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Re: [Microscope] Re: How Do I Change AC to DC in My AO 110 Illuminator

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  • J. Forster
    The bulb voltage is of no matter, except that for constant wattage, the higher voltage bulbs will have shorter thermal time constants, hence flicker more.
    Message 1 of 29 , Feb 14, 2013
      The bulb voltage is of no matter, except that for constant wattage, the
      higher voltage bulbs will have shorter thermal time constants, hence
      flicker more.

      -John

      =============



      > Ok, I thought we were dealing with a 6V bulb.
      >
      > Tony
      >
      > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
      >>
      >> Tony,
      >>
      >> It's not that simple.
      >>
      >> If you use a big capacitor, as you correctly suggest, the aim is to
      >> charge
      >> the cap up to the peak voltage on every half-cycle of line. The cap
      >> needs
      >> to be big enough that the voltage does not dip much before the next peak
      >> comes along.
      >>
      >> BUT, that means the capacitor stays charged to the full peak of the
      >> transformer output, which ius 0.5*SQR2 * RMS of transformer. If trhe
      >> transfoirmer secondary is 12 VRMS, the peak will be around 18VDC.
      >>
      >> The ulb will burn out just about instantly.
      >>
      >> If you are going to full-wave rectify and use a big filter, you must
      >> reduce to transformer output.
      >>
      >> Please see my previous post for good solutions.
      >>
      >> -John
      >>
      >> ===================
      >>
      >>
      >>
      >> > Don't forget folks that we're talking about something in the region of
      >> 6V
      >> > 20W. Which means about 3.3A. It should be possible to use the scope AC
      >> > output ( which will probably be around 10V AC off load) into a bridge
      >> > rated at say 10A ( be generous they're cheap) and a reservoir cap of
      >> > around 47000uF @16V (at least) working will produce very little
      >> ripple. (
      >> > around 250mv) Remember it's just the lamp filament and not the camera
      >> > that's running off this supply.
      >> > The problem comes when you want to build it all into the scope, as the
      >> cap
      >> > tends to be on the tubby side. It is possible to use two or more caps
      >> in
      >> > parallel which may ease space problems.
      >> >
      >> > regards
      >> >
      >> > Tony
      >> >
      >> > Reading UK
      >> >
      >> > --- In Microscope@yahoogroups.com, Chris Albertson wrote:
      >> >>
      >> >> Yes, you can buy a bridge reactifiier like in the data sheet. But
      >> four
      >> >> diodes will work as well. Cost about 1 to 5 cents each. Then you
      >> >> still
      >> >> don't have good DC. You need a filter cap and a regulator. And of
      >> >> course
      >> >> #1 most importance is the transformer.
      >> >>
      >> >> You can buy a good DC power supply with adjustable voltage for not a
      >> lot
      >> >> of
      >> >> money and you can build them too. The Googe term is "power supply".
      >> >> You
      >> >> can buy them already build on a circuit borad on eBay for maybe $10.
      >> >> Thefirst thing to decide is the range of voltages you need is it 2-6
      >> >> volts
      >> >> or 5-9 volts or whatever.
      >> >>
      >> >> There must be many people with enginerring degrees on this list who
      >> can
      >> >> help but a simple DC power supply is something you can learn to
      >> design
      >> >> and
      >> >> build assuming you know the basics of electronics. I absolutly
      >> >> recommend
      >> >> a regulated power supply if the goal is ripple fee DC. Those simple
      >> >> can
      >> >> cheap LM317 regulator chips cost under a buck and will produce nearly
      >> >> perfect, clean DC.
      >> >>
      >> >> You can build or buy but eBay makes buying the better option see item
      >> >> number 271153856438
      >> >> Look at the above in the product description is a classic schematic
      >> that
      >> >> shows you how to use that rectifier chip you found. As you can see
      >> if
      >> >> is
      >> >> just the first part of a larger circuit. But you can buy it all for
      >> >> $10.
      >> >>
      >> >>
      >> >>
      >> >> On Thu, Feb 14, 2013 at 6:23 AM, Elliot Kirschbaum
      >> >> wrote:
      >> >>
      >> >> > **
      >> >> >
      >> >> >
      >> >> > This is a followup to my post on "What Can I Do About Electrical
      >> >> > Interference?"
      >> >> >
      >> >> > Tony gets first prize. I did the experiment he suggested. No
      >> >> interference
      >> >> > using natural light with the electronics running. Take the mirror
      >> away
      >> >> so
      >> >> > the light is from the lamp and the interference pattern resumes. So
      >> >> the
      >> >> > interference pattern is generated by the lamp.
      >> >> >
      >> >> > So what do I do now? Is it simply a matter of putting a diode
      >> bridge
      >> >> > rectifier and a smoothing capacitor between the transformer and the
      >> >> lamp?
      >> >> >
      >> >> > I have posted a picture of such as circuit in Elliot's Microscope
      >> >> folder
      >> >> > http://tinyurl.com/abew7op
      >> >> >
      >> >> > The rectifier in that circuit uses a Toshiba 1B4B42 bridge
      >> rectifier.
      >> >> The
      >> >> > data sheet for which can be found at the following URL
      >> >> >
      >> >> > http://www.alldatasheet.com/datasheet-pdf/pdf/29740/TOSHIBA/1B4B42.html
      >> >> >
      >> >> > Will this work to change the 6V AC to 6V DC in my AO 110
      >> Illuminator?
      >> >> >
      >> >> > How big is this thing? Will it fit inside the base?
      >> >> >
      >> >> > Are the values for C1 and R1 in the circuit what I should use to
      >> >> smooth
      >> >> > the DC output, even though V1 in my application is 6V rather than
      >> 12,
      >> >> and
      >> >> > it may be at 60Hz rather than 50Hz?
      >> >> >
      >> >> > Any help, other than telling me to take a college level course in
      >> >> > electronics, will be appreciated.
      >> >> >
      >> >> > --
      >> >> > Elliot
      >> >> >
      >> >> > --
      >> >> > Elliot Kirschbaum
      >> >> > Shepherdstown, WV
      >> >> > kingfisher501 at gmail dot com
      >> >> >
      >> >> > [Non-text portions of this message have been removed]
      >> >> >
      >> >> >
      >> >> >
      >> >>
      >> >>
      >> >>
      >> >> --
      >> >>
      >> >> Chris Albertson
      >> >> Redondo Beach, California
      >> >>
      >> >>
      >> >> [Non-text portions of this message have been removed]
      >> >>
      >> >
      >> >
      >> >
      >>
      >
      >
      >
    • Tony
      Ah well, I ve given up on bulbs. Here s my newest conversion of my Swift inverted.
      Message 2 of 29 , Feb 14, 2013
        Ah well, I've given up on bulbs. Here's my newest conversion of my Swift inverted.

        http://groups.yahoo.com/group/Microscope/photos/album/353933373/pic/231628664/view

        Tony

        Reading UK

        --- In Microscope@yahoogroups.com, "J. Forster" wrote:
        >
        > The bulb voltage is of no matter, except that for constant wattage, the
        > higher voltage bulbs will have shorter thermal time constants, hence
        > flicker more.
        >
        > -John
        >
        > =============
        >
        >
        >
        > > Ok, I thought we were dealing with a 6V bulb.
        > >
        > > Tony
        > >
        > > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
        > >>
        > >> Tony,
        > >>
        > >> It's not that simple.
        > >>
        > >> If you use a big capacitor, as you correctly suggest, the aim is to
        > >> charge
        > >> the cap up to the peak voltage on every half-cycle of line. The cap
        > >> needs
        > >> to be big enough that the voltage does not dip much before the next peak
        > >> comes along.
        > >>
        > >> BUT, that means the capacitor stays charged to the full peak of the
        > >> transformer output, which ius 0.5*SQR2 * RMS of transformer. If trhe
        > >> transfoirmer secondary is 12 VRMS, the peak will be around 18VDC.
        > >>
        > >> The ulb will burn out just about instantly.
        > >>
        > >> If you are going to full-wave rectify and use a big filter, you must
        > >> reduce to transformer output.
        > >>
        > >> Please see my previous post for good solutions.
        > >>
        > >> -John
        > >>
        > >> ===================
        > >>
        > >>
        > >>
        > >> > Don't forget folks that we're talking about something in the region of
        > >> 6V
        > >> > 20W. Which means about 3.3A. It should be possible to use the scope AC
        > >> > output ( which will probably be around 10V AC off load) into a bridge
        > >> > rated at say 10A ( be generous they're cheap) and a reservoir cap of
        > >> > around 47000uF @16V (at least) working will produce very little
        > >> ripple. (
        > >> > around 250mv) Remember it's just the lamp filament and not the camera
        > >> > that's running off this supply.
        > >> > The problem comes when you want to build it all into the scope, as the
        > >> cap
        > >> > tends to be on the tubby side. It is possible to use two or more caps
        > >> in
        > >> > parallel which may ease space problems.
        > >> >
        > >> > regards
        > >> >
        > >> > Tony
        > >> >
        > >> > Reading UK
        > >> >
        > >> > --- In Microscope@yahoogroups.com, Chris Albertson wrote:
        > >> >>
        > >> >> Yes, you can buy a bridge reactifiier like in the data sheet. But
        > >> four
        > >> >> diodes will work as well. Cost about 1 to 5 cents each. Then you
        > >> >> still
        > >> >> don't have good DC. You need a filter cap and a regulator. And of
        > >> >> course
        > >> >> #1 most importance is the transformer.
        > >> >>
        > >> >> You can buy a good DC power supply with adjustable voltage for not a
        > >> lot
        > >> >> of
        > >> >> money and you can build them too. The Googe term is "power supply".
        > >> >> You
        > >> >> can buy them already build on a circuit borad on eBay for maybe $10.
        > >> >> Thefirst thing to decide is the range of voltages you need is it 2-6
        > >> >> volts
        > >> >> or 5-9 volts or whatever.
        > >> >>
        > >> >> There must be many people with enginerring degrees on this list who
        > >> can
        > >> >> help but a simple DC power supply is something you can learn to
        > >> design
        > >> >> and
        > >> >> build assuming you know the basics of electronics. I absolutly
        > >> >> recommend
        > >> >> a regulated power supply if the goal is ripple fee DC. Those simple
        > >> >> can
        > >> >> cheap LM317 regulator chips cost under a buck and will produce nearly
        > >> >> perfect, clean DC.
        > >> >>
        > >> >> You can build or buy but eBay makes buying the better option see item
        > >> >> number 271153856438
        > >> >> Look at the above in the product description is a classic schematic
        > >> that
        > >> >> shows you how to use that rectifier chip you found. As you can see
        > >> if
        > >> >> is
        > >> >> just the first part of a larger circuit. But you can buy it all for
        > >> >> $10.
        > >> >>
        > >> >>
        > >> >>
        > >> >> On Thu, Feb 14, 2013 at 6:23 AM, Elliot Kirschbaum
        > >> >> wrote:
        > >> >>
        > >> >> > **
        > >> >> >
        > >> >> >
        > >> >> > This is a followup to my post on "What Can I Do About Electrical
        > >> >> > Interference?"
        > >> >> >
        > >> >> > Tony gets first prize. I did the experiment he suggested. No
        > >> >> interference
        > >> >> > using natural light with the electronics running. Take the mirror
        > >> away
        > >> >> so
        > >> >> > the light is from the lamp and the interference pattern resumes. So
        > >> >> the
        > >> >> > interference pattern is generated by the lamp.
        > >> >> >
        > >> >> > So what do I do now? Is it simply a matter of putting a diode
        > >> bridge
        > >> >> > rectifier and a smoothing capacitor between the transformer and the
        > >> >> lamp?
        > >> >> >
        > >> >> > I have posted a picture of such as circuit in Elliot's Microscope
        > >> >> folder
        > >> >> > http://tinyurl.com/abew7op
        > >> >> >
        > >> >> > The rectifier in that circuit uses a Toshiba 1B4B42 bridge
        > >> rectifier.
        > >> >> The
        > >> >> > data sheet for which can be found at the following URL
        > >> >> >
        > >> >> > http://www.alldatasheet.com/datasheet-pdf/pdf/29740/TOSHIBA/1B4B42.html
        > >> >> >
        > >> >> > Will this work to change the 6V AC to 6V DC in my AO 110
        > >> Illuminator?
        > >> >> >
        > >> >> > How big is this thing? Will it fit inside the base?
        > >> >> >
        > >> >> > Are the values for C1 and R1 in the circuit what I should use to
        > >> >> smooth
        > >> >> > the DC output, even though V1 in my application is 6V rather than
        > >> 12,
        > >> >> and
        > >> >> > it may be at 60Hz rather than 50Hz?
        > >> >> >
        > >> >> > Any help, other than telling me to take a college level course in
        > >> >> > electronics, will be appreciated.
        > >> >> >
        > >> >> > --
        > >> >> > Elliot
        > >> >> >
        > >> >> > --
        > >> >> > Elliot Kirschbaum
        > >> >> > Shepherdstown, WV
        > >> >> > kingfisher501 at gmail dot com
        > >> >> >
        > >> >> > [Non-text portions of this message have been removed]
        > >> >> >
        > >> >> >
        > >> >> >
        > >> >>
        > >> >>
        > >> >>
        > >> >> --
        > >> >>
        > >> >> Chris Albertson
        > >> >> Redondo Beach, California
        > >> >>
        > >> >>
        > >> >> [Non-text portions of this message have been removed]
        > >> >>
        > >> >
        > >> >
        > >> >
        > >>
        > >
        > >
        > >
        >
      • Dave McGuire
        ... Absolutely...that s why I prefaced that with if I were doing this for myself . :) Ya gotta admit, though, that that would ve made one heck of a nice
        Message 3 of 29 , Feb 14, 2013
          On 02/14/2013 02:45 PM, J. Forster wrote:
          > A home brew regulator might be fine for an electronics guy, but not so
          > much for someone w/o electronic expoerience.

          Absolutely...that's why I prefaced that with "if I were doing this for
          myself". :) Ya gotta admit, though, that that would've made one heck of
          a nice stabilized illuminator!

          I might build one of those for my Vickers Photoplan. Its two
          lamphouses are powered by the most "lowbrow" power supply I've ever
          seen...it was clearly a matter of a great microscope company getting
          just about ready to ship a new product, when someone said, "oh wait,
          that's right, we need some of this ELECTRIC stuff in here to make these
          bulbs light up!" ;)

          > I'd use a 15-20 VDC unregulated DC supply, and a little Chinese step-down
          > switching regulator like eBay 150989421790. This is just an example, not a
          > specific reccomendation.

          That's a nice-looking module.

          > A switching regulator is a better choice than a linear regulator, because
          > of power dissipation and simplicity.

          Agreed 100%. Unless of course you want it to double as a space heater. ;)

          One approach I've used in the past to get close to the best of both
          worlds (efficiency and clean output) is to use a switching regulator
          followed by a low-dropout linear post-regulator. The switching
          regulator gets the voltage low enough, at typically 85-95+% efficiency,
          so that the LDO doesn't end up having to do much.

          -Dave

          --
          Dave McGuire, AK4HZ
          New Kensington, PA
        • billbillt_2000
          Tony, Looks to me you did the wisest thing converting to LED.. BillT
          Message 4 of 29 , Feb 14, 2013
            Tony,
            Looks to me you did the wisest thing converting to LED..
            BillT
            --- In Microscope@yahoogroups.com, "Tony" wrote:
            >
            > Ah well, I've given up on bulbs. Here's my newest conversion of my Swift inverted.
            >
            > http://groups.yahoo.com/group/Microscope/photos/album/353933373/pic/231628664/view
            >
            > Tony
            >
            > Reading UK
            >
            > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
            > >
            > > The bulb voltage is of no matter, except that for constant wattage, the
            > > higher voltage bulbs will have shorter thermal time constants, hence
            > > flicker more.
            > >
            > > -John
            > >
            > > =============
            > >
            > >
            > >
            > > > Ok, I thought we were dealing with a 6V bulb.
            > > >
            > > > Tony
            > > >
            > > > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
            > > >>
            > > >> Tony,
            > > >>
            > > >> It's not that simple.
            > > >>
            > > >> If you use a big capacitor, as you correctly suggest, the aim is to
            > > >> charge
            > > >> the cap up to the peak voltage on every half-cycle of line. The cap
            > > >> needs
            > > >> to be big enough that the voltage does not dip much before the next peak
            > > >> comes along.
            > > >>
            > > >> BUT, that means the capacitor stays charged to the full peak of the
            > > >> transformer output, which ius 0.5*SQR2 * RMS of transformer. If trhe
            > > >> transfoirmer secondary is 12 VRMS, the peak will be around 18VDC.
            > > >>
            > > >> The ulb will burn out just about instantly.
            > > >>
            > > >> If you are going to full-wave rectify and use a big filter, you must
            > > >> reduce to transformer output.
            > > >>
            > > >> Please see my previous post for good solutions.
            > > >>
            > > >> -John
            > > >>
            > > >> ===================
            > > >>
            > > >>
            > > >>
            > > >> > Don't forget folks that we're talking about something in the region of
            > > >> 6V
            > > >> > 20W. Which means about 3.3A. It should be possible to use the scope AC
            > > >> > output ( which will probably be around 10V AC off load) into a bridge
            > > >> > rated at say 10A ( be generous they're cheap) and a reservoir cap of
            > > >> > around 47000uF @16V (at least) working will produce very little
            > > >> ripple. (
            > > >> > around 250mv) Remember it's just the lamp filament and not the camera
            > > >> > that's running off this supply.
            > > >> > The problem comes when you want to build it all into the scope, as the
            > > >> cap
            > > >> > tends to be on the tubby side. It is possible to use two or more caps
            > > >> in
            > > >> > parallel which may ease space problems.
            > > >> >
            > > >> > regards
            > > >> >
            > > >> > Tony
            > > >> >
            > > >> > Reading UK
            > > >> >
            > > >> > --- In Microscope@yahoogroups.com, Chris Albertson wrote:
            > > >> >>
            > > >> >> Yes, you can buy a bridge reactifiier like in the data sheet. But
            > > >> four
            > > >> >> diodes will work as well. Cost about 1 to 5 cents each. Then you
            > > >> >> still
            > > >> >> don't have good DC. You need a filter cap and a regulator. And of
            > > >> >> course
            > > >> >> #1 most importance is the transformer.
            > > >> >>
            > > >> >> You can buy a good DC power supply with adjustable voltage for not a
            > > >> lot
            > > >> >> of
            > > >> >> money and you can build them too. The Googe term is "power supply".
            > > >> >> You
            > > >> >> can buy them already build on a circuit borad on eBay for maybe $10.
            > > >> >> Thefirst thing to decide is the range of voltages you need is it 2-6
            > > >> >> volts
            > > >> >> or 5-9 volts or whatever.
            > > >> >>
            > > >> >> There must be many people with enginerring degrees on this list who
            > > >> can
            > > >> >> help but a simple DC power supply is something you can learn to
            > > >> design
            > > >> >> and
            > > >> >> build assuming you know the basics of electronics. I absolutly
            > > >> >> recommend
            > > >> >> a regulated power supply if the goal is ripple fee DC. Those simple
            > > >> >> can
            > > >> >> cheap LM317 regulator chips cost under a buck and will produce nearly
            > > >> >> perfect, clean DC.
            > > >> >>
            > > >> >> You can build or buy but eBay makes buying the better option see item
            > > >> >> number 271153856438
            > > >> >> Look at the above in the product description is a classic schematic
            > > >> that
            > > >> >> shows you how to use that rectifier chip you found. As you can see
            > > >> if
            > > >> >> is
            > > >> >> just the first part of a larger circuit. But you can buy it all for
            > > >> >> $10.
            > > >> >>
            > > >> >>
            > > >> >>
            > > >> >> On Thu, Feb 14, 2013 at 6:23 AM, Elliot Kirschbaum
            > > >> >> wrote:
            > > >> >>
            > > >> >> > **
            > > >> >> >
            > > >> >> >
            > > >> >> > This is a followup to my post on "What Can I Do About Electrical
            > > >> >> > Interference?"
            > > >> >> >
            > > >> >> > Tony gets first prize. I did the experiment he suggested. No
            > > >> >> interference
            > > >> >> > using natural light with the electronics running. Take the mirror
            > > >> away
            > > >> >> so
            > > >> >> > the light is from the lamp and the interference pattern resumes. So
            > > >> >> the
            > > >> >> > interference pattern is generated by the lamp.
            > > >> >> >
            > > >> >> > So what do I do now? Is it simply a matter of putting a diode
            > > >> bridge
            > > >> >> > rectifier and a smoothing capacitor between the transformer and the
            > > >> >> lamp?
            > > >> >> >
            > > >> >> > I have posted a picture of such as circuit in Elliot's Microscope
            > > >> >> folder
            > > >> >> > http://tinyurl.com/abew7op
            > > >> >> >
            > > >> >> > The rectifier in that circuit uses a Toshiba 1B4B42 bridge
            > > >> rectifier.
            > > >> >> The
            > > >> >> > data sheet for which can be found at the following URL
            > > >> >> >
            > > >> >> > http://www.alldatasheet.com/datasheet-pdf/pdf/29740/TOSHIBA/1B4B42.html
            > > >> >> >
            > > >> >> > Will this work to change the 6V AC to 6V DC in my AO 110
            > > >> Illuminator?
            > > >> >> >
            > > >> >> > How big is this thing? Will it fit inside the base?
            > > >> >> >
            > > >> >> > Are the values for C1 and R1 in the circuit what I should use to
            > > >> >> smooth
            > > >> >> > the DC output, even though V1 in my application is 6V rather than
            > > >> 12,
            > > >> >> and
            > > >> >> > it may be at 60Hz rather than 50Hz?
            > > >> >> >
            > > >> >> > Any help, other than telling me to take a college level course in
            > > >> >> > electronics, will be appreciated.
            > > >> >> >
            > > >> >> > --
            > > >> >> > Elliot
            > > >> >> >
            > > >> >> > --
            > > >> >> > Elliot Kirschbaum
            > > >> >> > Shepherdstown, WV
            > > >> >> > kingfisher501 at gmail dot com
            > > >> >> >
            > > >> >> > [Non-text portions of this message have been removed]
            > > >> >> >
            > > >> >> >
            > > >> >> >
            > > >> >>
            > > >> >>
            > > >> >>
            > > >> >> --
            > > >> >>
            > > >> >> Chris Albertson
            > > >> >> Redondo Beach, California
            > > >> >>
            > > >> >>
            > > >> >> [Non-text portions of this message have been removed]
            > > >> >>
            > > >> >
            > > >> >
            > > >> >
            > > >>
            > > >
            > > >
            > > >
            > >
            >
          • J. Forster
            You can regulate the light source, or auto-adjust the integrated light to the sensor. The Zeiss MC-63 does the latter and has a photocell and beamsplitter in
            Message 5 of 29 , Feb 14, 2013
              You can regulate the light source, or auto-adjust the integrated light to
              the sensor. The Zeiss MC-63 does the latter and has a photocell and
              beamsplitter in the optical path to the camera.

              A post-regulator is not needed in this application. It's overkill. The
              lamp supply has to be ripple free, but high frequency switching trash and
              other noise is too high frequency to make it through the Low Pass Filter
              of the lamp filament.

              The switching pre-reg and DC/DC converter has been used in the aerospace
              business for >40 years, where the objective is to maximize spacecraft
              battery life.

              -John

              ======================




              > On 02/14/2013 02:45 PM, J. Forster wrote:
              >> A home brew regulator might be fine for an electronics guy, but not so
              >> much for someone w/o electronic expoerience.
              >
              > Absolutely...that's why I prefaced that with "if I were doing this for
              > myself". :) Ya gotta admit, though, that that would've made one heck of
              > a nice stabilized illuminator!
              >
              > I might build one of those for my Vickers Photoplan. Its two
              > lamphouses are powered by the most "lowbrow" power supply I've ever
              > seen...it was clearly a matter of a great microscope company getting
              > just about ready to ship a new product, when someone said, "oh wait,
              > that's right, we need some of this ELECTRIC stuff in here to make these
              > bulbs light up!" ;)
              >
              >> I'd use a 15-20 VDC unregulated DC supply, and a little Chinese
              >> step-down
              >> switching regulator like eBay 150989421790. This is just an example, not
              >> a
              >> specific reccomendation.
              >
              > That's a nice-looking module.
              >
              >> A switching regulator is a better choice than a linear regulator,
              >> because
              >> of power dissipation and simplicity.
              >
              > Agreed 100%. Unless of course you want it to double as a space heater.
              > ;)
              >
              > One approach I've used in the past to get close to the best of both
              > worlds (efficiency and clean output) is to use a switching regulator
              > followed by a low-dropout linear post-regulator. The switching
              > regulator gets the voltage low enough, at typically 85-95+% efficiency,
              > so that the LDO doesn't end up having to do much.
              >
              > -Dave
              >
              > --
              > Dave McGuire, AK4HZ
              > New Kensington, PA
              >
            • John
              When a bridge rectifier is used on a transformer that just has 2 wires coming out of it the peak voltage on the smoothing capacitor wont reach root 2 times the
              Message 6 of 29 , Feb 14, 2013
                When a bridge rectifier is used on a transformer that just has 2 wires coming out of it the peak voltage on the smoothing capacitor wont reach root 2 times the supply. It's generally about 1.1 times and will drop under load - that can make capacitors blow up when the load is low and the transformer has very poor load regulation. It's best to check the open circuit voltage of the transformer before choosing capacitors for smoothing. The diode voltage drop also reduces the output voltage and in real terms with a 6v transformer you probably wont get 6v on the output. In fact it's likely to be under 5. It will be lower under load.

                Voltage regulators make matters worse. There are low drop types but even these need in excess of 1/2 volt drop across them to work.These can be very touchy to use as well. Normal types will quite likely need 2v or more across them.

                If you happen to have say a 6-0-6 v transformer and use the usual 2 diode rectifier for these they may give 1.414 less diode drops after smoothing with capacitors.

                Poor old diodes will be taking several amps in this sort of set up and it would be best to use one of the larger encapsulated bridge rectifiers. In this case one of the ones in a square metal "box" with 4 spade terminals sticking out. While some bridge recifiers may say 4 amp etc this will as with most electronics specs when mounted on an infinite heat sink. Worse still it might be a commercial spec which would mean that it would get exceedingly hot even on this ficticious heat sink. People get away with this sort of thing as the parts are better than the spec but it's a good idea to be cautious. The same is true of transformers except the way they are rated varies. You might buy a 1amp type for instance and find it has a temperature rise of in excess of 80C when fully loaded.

                This however sounds like the Tucsen camera problem. The simplest solution is to keep the lamp well up and use a neutral density filter. Maybe playing with the camera gain which is always too high and setting the exposure time yourself. The reason for this is a thyristor drives to the lamp. They switch on for a period in each mains cycle. The period sets the average intensity of the lamp. Cameras are very sensitive so are used with the lamp well down so the period of no drive to the lamp is long. If you DC a scope like that you wont have lighting control any more. The easiest way to dc drive the bulb in a scope like that is too use an external DC power supply. That is fairly cost effective with some 12v or so adjustable supplies that are intended for amateur radio types but some of them wont power up into a bulb even when the voltage is turned right down - these generally wont go down to zero volts as that costs money.

                John


                --- In Microscope@yahoogroups.com, "Tony" wrote:
                >
                > Ah well, I've given up on bulbs. Here's my newest conversion of my Swift inverted.
                >
                > http://groups.yahoo.com/group/Microscope/photos/album/353933373/pic/231628664/view
                >
                > Tony
                >
                > Reading UK
                >
                > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
                > >
                > > The bulb voltage is of no matter, except that for constant wattage, the
                > > higher voltage bulbs will have shorter thermal time constants, hence
                > > flicker more.
                > >
                > > -John
                > >
                > > =============
                > >
                > >
                > >
                > > > Ok, I thought we were dealing with a 6V bulb.
                > > >
                > > > Tony
                > > >
                > > > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
                > > >>
                > > >> Tony,
                > > >>
                > > >> It's not that simple.
                > > >>
                > > >> If you use a big capacitor, as you correctly suggest, the aim is to
                > > >> charge
                > > >> the cap up to the peak voltage on every half-cycle of line. The cap
                > > >> needs
                > > >> to be big enough that the voltage does not dip much before the next peak
                > > >> comes along.
                > > >>
                > > >> BUT, that means the capacitor stays charged to the full peak of the
                > > >> transformer output, which ius 0.5*SQR2 * RMS of transformer. If trhe
                > > >> transfoirmer secondary is 12 VRMS, the peak will be around 18VDC.
                > > >>
                > > >> The ulb will burn out just about instantly.
                > > >>
                > > >> If you are going to full-wave rectify and use a big filter, you must
                > > >> reduce to transformer output.
                > > >>
                > > >> Please see my previous post for good solutions.
                > > >>
                > > >> -John
                > > >>
                > > >> ===================
                > > >>
                > > >>
                > > >>
                > > >> > Don't forget folks that we're talking about something in the region of
                > > >> 6V
                > > >> > 20W. Which means about 3.3A. It should be possible to use the scope AC
                > > >> > output ( which will probably be around 10V AC off load) into a bridge
                > > >> > rated at say 10A ( be generous they're cheap) and a reservoir cap of
                > > >> > around 47000uF @16V (at least) working will produce very little
                > > >> ripple. (
                > > >> > around 250mv) Remember it's just the lamp filament and not the camera
                > > >> > that's running off this supply.
                > > >> > The problem comes when you want to build it all into the scope, as the
                > > >> cap
                > > >> > tends to be on the tubby side. It is possible to use two or more caps
                > > >> in
                > > >> > parallel which may ease space problems.
                > > >> >
                > > >> > regards
                > > >> >
                > > >> > Tony
                > > >> >
                > > >> > Reading UK
                > > >> >
                > > >> > --- In Microscope@yahoogroups.com, Chris Albertson wrote:
                > > >> >>
                > > >> >> Yes, you can buy a bridge reactifiier like in the data sheet. But
                > > >> four
                > > >> >> diodes will work as well. Cost about 1 to 5 cents each. Then you
                > > >> >> still
                > > >> >> don't have good DC. You need a filter cap and a regulator. And of
                > > >> >> course
                > > >> >> #1 most importance is the transformer.
                > > >> >>
                > > >> >> You can buy a good DC power supply with adjustable voltage for not a
                > > >> lot
                > > >> >> of
                > > >> >> money and you can build them too. The Googe term is "power supply".
                > > >> >> You
                > > >> >> can buy them already build on a circuit borad on eBay for maybe $10.
                > > >> >> Thefirst thing to decide is the range of voltages you need is it 2-6
                > > >> >> volts
                > > >> >> or 5-9 volts or whatever.
                > > >> >>
                > > >> >> There must be many people with enginerring degrees on this list who
                > > >> can
                > > >> >> help but a simple DC power supply is something you can learn to
                > > >> design
                > > >> >> and
                > > >> >> build assuming you know the basics of electronics. I absolutly
                > > >> >> recommend
                > > >> >> a regulated power supply if the goal is ripple fee DC. Those simple
                > > >> >> can
                > > >> >> cheap LM317 regulator chips cost under a buck and will produce nearly
                > > >> >> perfect, clean DC.
                > > >> >>
                > > >> >> You can build or buy but eBay makes buying the better option see item
                > > >> >> number 271153856438
                > > >> >> Look at the above in the product description is a classic schematic
                > > >> that
                > > >> >> shows you how to use that rectifier chip you found. As you can see
                > > >> if
                > > >> >> is
                > > >> >> just the first part of a larger circuit. But you can buy it all for
                > > >> >> $10.
                > > >> >>
                > > >> >>
                > > >> >>
                > > >> >> On Thu, Feb 14, 2013 at 6:23 AM, Elliot Kirschbaum
                > > >> >> wrote:
                > > >> >>
                > > >> >> > **
                > > >> >> >
                > > >> >> >
                > > >> >> > This is a followup to my post on "What Can I Do About Electrical
                > > >> >> > Interference?"
                > > >> >> >
                > > >> >> > Tony gets first prize. I did the experiment he suggested. No
                > > >> >> interference
                > > >> >> > using natural light with the electronics running. Take the mirror
                > > >> away
                > > >> >> so
                > > >> >> > the light is from the lamp and the interference pattern resumes. So
                > > >> >> the
                > > >> >> > interference pattern is generated by the lamp.
                > > >> >> >
                > > >> >> > So what do I do now? Is it simply a matter of putting a diode
                > > >> bridge
                > > >> >> > rectifier and a smoothing capacitor between the transformer and the
                > > >> >> lamp?
                > > >> >> >
                > > >> >> > I have posted a picture of such as circuit in Elliot's Microscope
                > > >> >> folder
                > > >> >> > http://tinyurl.com/abew7op
                > > >> >> >
                > > >> >> > The rectifier in that circuit uses a Toshiba 1B4B42 bridge
                > > >> rectifier.
                > > >> >> The
                > > >> >> > data sheet for which can be found at the following URL
                > > >> >> >
                > > >> >> > http://www.alldatasheet.com/datasheet-pdf/pdf/29740/TOSHIBA/1B4B42.html
                > > >> >> >
                > > >> >> > Will this work to change the 6V AC to 6V DC in my AO 110
                > > >> Illuminator?
                > > >> >> >
                > > >> >> > How big is this thing? Will it fit inside the base?
                > > >> >> >
                > > >> >> > Are the values for C1 and R1 in the circuit what I should use to
                > > >> >> smooth
                > > >> >> > the DC output, even though V1 in my application is 6V rather than
                > > >> 12,
                > > >> >> and
                > > >> >> > it may be at 60Hz rather than 50Hz?
                > > >> >> >
                > > >> >> > Any help, other than telling me to take a college level course in
                > > >> >> > electronics, will be appreciated.
                > > >> >> >
                > > >> >> > --
                > > >> >> > Elliot
                > > >> >> >
                > > >> >> > --
                > > >> >> > Elliot Kirschbaum
                > > >> >> > Shepherdstown, WV
                > > >> >> > kingfisher501 at gmail dot com
                > > >> >> >
                > > >> >> > [Non-text portions of this message have been removed]
                > > >> >> >
                > > >> >> >
                > > >> >> >
                > > >> >>
                > > >> >>
                > > >> >>
                > > >> >> --
                > > >> >>
                > > >> >> Chris Albertson
                > > >> >> Redondo Beach, California
                > > >> >>
                > > >> >>
                > > >> >> [Non-text portions of this message have been removed]
                > > >> >>
                > > >> >
                > > >> >
                > > >> >
                > > >>
                > > >
                > > >
                > > >
                > >
                >
              • Dave McGuire
                ... Oh, VERY nice! ... I wasn t suggesting it for this application; I was just describing a technique I d used for clean power supplies. Of course the
                Message 7 of 29 , Feb 14, 2013
                  On 02/14/2013 03:55 PM, J. Forster wrote:
                  > You can regulate the light source, or auto-adjust the integrated light to
                  > the sensor. The Zeiss MC-63 does the latter and has a photocell and
                  > beamsplitter in the optical path to the camera.

                  Oh, VERY nice!

                  > A post-regulator is not needed in this application. It's overkill. The
                  > lamp supply has to be ripple free, but high frequency switching trash and
                  > other noise is too high frequency to make it through the Low Pass Filter
                  > of the lamp filament.

                  I wasn't suggesting it for this application; I was just describing a
                  technique I'd used for clean power supplies. Of course the switching
                  trash won't affect the lamp, but it can certainly create a lot of EMI/RFI.

                  > The switching pre-reg and DC/DC converter has been used in the aerospace
                  > business for >40 years, where the objective is to maximize spacecraft
                  > battery life.

                  I use it to great advantage today in power-consumption-sensitive
                  analog stuff like sensor interfacing. It's a nice technique.

                  -Dave

                  --
                  Dave McGuire, AK4HZ
                  New Kensington, PA
                • J. Forster
                  The 1.1 number is ex rectum, but this group is not the place to argue the matter. The filter caps will charge to SQR2 times the RMS of the transformer, minus
                  Message 8 of 29 , Feb 14, 2013
                    The 1.1 number is ex rectum, but this group is not the place to argue the
                    matter.

                    The filter caps will charge to SQR2 times the RMS of the transformer,
                    minus the diode drop(s), either 0.6V or 1.2V, depending on the connection.
                    I(f there is a lot of ripple, the filter cap0s need to be bigger.

                    -John

                    =================



                    > When a bridge rectifier is used on a transformer that just has 2 wires
                    > coming out of it the peak voltage on the smoothing capacitor wont reach
                    > root 2 times the supply. It's generally about 1.1 times and will drop
                    > under load - that can make capacitors blow up when the load is low and
                    the transformer has very poor load regulation.

                    [snip]
                  • Elliot Kirschbaum
                    ... Thanks Chris I believe that I need a range of 4-6 volts. (See my post in response to John Foster) I looked at the schematic and saw three inputs: 2 AC
                    Message 9 of 29 , Feb 14, 2013
                      On Feb 14, 2013, at 11:26 AM, Chris Albertson <albertson.chris@...> wrote:

                      > You can buy a good DC power supply with adjustable voltage for not a lot of
                      > money and you can build them too. The Googe term is "power supply". You
                      > can buy them already build on a circuit borad on eBay for maybe $10.
                      > Thefirst thing to decide is the range of voltages you need is it 2-6 volts
                      > or 5-9 volts or whatever.
                      >
                      > There must be many people with enginerring degrees on this list who can
                      > help but a simple DC power supply is something you can learn to design and
                      > build assuming you know the basics of electronics. I absolutly recommend
                      > a regulated power supply if the goal is ripple fee DC. Those simple can
                      > cheap LM317 regulator chips cost under a buck and will produce nearly
                      > perfect, clean DC.
                      >
                      > You can build or buy but eBay makes buying the better option see item
                      > number 271153856438
                      > Look at the above in the product description is a classic schematic that
                      > shows you how to use that rectifier chip you found. As you can see if is
                      > just the first part of a larger circuit. But you can buy it all for $10.

                      Thanks Chris

                      I believe that I need a range of 4-6 volts. (See my post in response to John Foster)

                      I looked at the schematic and saw three inputs: 2 AC inputs and 1 DC input. I would only have the 2 AC inputs, which I want converted to ripple free DC. I assume that the lamp would be connected to the DC output and the ground.

                      --
                      Elliot

                      --
                      Elliot Kirschbaum
                      Shepherdstown, WV
                      kingfisher501 at gmail dot com





                      [Non-text portions of this message have been removed]
                    • Elliot Kirschbaum
                      Thanks for the response John. ... 6V 20W The transformer is continuously variable from 4V to 6V. ... I would appreciate that. Here is everything that I know
                      Message 10 of 29 , Feb 14, 2013
                        Thanks for the response John.

                        On Feb 14, 2013, at 11:26 AM, "J. Forster" <jfor@...> wrote:

                        > Well, I am an EE and have a degree from MIT to prove it.
                        >
                        > 'Filtering' the AC will do nothing.
                        >
                        > With respect to the full wave bridge:
                        >
                        > 1. There is no need at all for the resistor, if the thing is connected to
                        > a lamp load.
                        >
                        > 2. The capacitor is far, far too small and will do essentially nothing.
                        >
                        > What is the voltage and wattage of the lamp?

                        6V 20W

                        The transformer is continuously variable from 4V to 6V.

                        >
                        > I would suggest using a high frequency switching regulator module from
                        > eBay. If you post your lamp characteristics, I'll help you pic one.

                        I would appreciate that. Here is everything that I know about the lamp:

                        The AO Series One-Ten Microstar Reference Manual says that the "Illuminator contains a high intensity 6V, 20W Tungsten Halogen lamp (Cat. No. 1120)�."

                        The Reference Manual also says that the "Illuminator has a continuously variable transformer with voltage markings for 4, 4.5, 5 and 6 volts�."

                        Actually, there is no 5 volt marking. The space between 4.5 and 6 is marked 5.5

                        psneely's website says that any of the following, available from AtlanticLightBulbs.com can be used.

                        AMERICAN OPTICAL 7388 $3.70 (as of 9/05)

                        AtlantaLightBulbs.com ESB
                        ESB - 20W T3 6V G4 BASE OSRAM ESB CROSS TO: 7388/FHE HALOGEN (ALB-UPC: 4050300012407)


                        AMERICAN OPTICAL ONE-10 $3.04 (as of 9/05)

                        The BulbMatrix Has Found a Value Replacement for AMERICAN OPTICAL ONE-10
                        ESB - 20W T3 6V G4 BASE OSRAM ESB CROSS TO: 7388/FHE HALOGEN This is a BulbMatrix Value Replacement. (ALB-UPC: 4050300012407)


                        AMERICAN OPTICAL 1120 $7.88 (as of 9/05)


                        The bulb that is actually in the base now, however, is a Philips 6605 10W 6V Projector Light Bulb.





                        >
                        > There are two other alternatives:
                        >
                        > 1. Use an external DC supply.
                        > 2. Use the full-wave bridge, a bigger capacitor,m and a linear regulator IC.

                        Do either of these alternatives have advantages over the regulator module?



                        Elliot

                        --
                        Elliot Kirschbaum
                        Shepherdstown, WV
                        kingfisher500 at comcast dot net



                        --
                        Elliot

                        --
                        Elliot Kirschbaum
                        Shepherdstown, WV
                        kingfisher501 at gmail dot com





                        [Non-text portions of this message have been removed]
                      • Elliot Kirschbaum
                        ... I am willing to put something outside the base if need be. -- Elliot -- Elliot Kirschbaum Shepherdstown, WV kingfisher501 at gmail dot com [Non-text
                        Message 11 of 29 , Feb 14, 2013
                          On Feb 14, 2013, at 12:37 PM, Tony <tony.pattinson@...> wrote:

                          > Don't forget folks that we're talking about something in the region of 6V 20W. Which means about 3.3A. It should be possible to use the scope AC output ( which will probably be around 10V AC off load) into a bridge rated at say 10A ( be generous they're cheap) and a reservoir cap of around 47000uF @16V (at least) working will produce very little ripple. ( around 250mv) Remember it's just the lamp filament and not the camera that's running off this supply.
                          > The problem comes when you want to build it all into the scope, as the cap tends to be on the tubby side. It is possible to use two or more caps in parallel which may ease space problems.


                          I am willing to put something outside the base if need be.

                          --
                          Elliot

                          --
                          Elliot Kirschbaum
                          Shepherdstown, WV
                          kingfisher501 at gmail dot com





                          [Non-text portions of this message have been removed]
                        • Elliot Kirschbaum
                          ... Aren t these things usually rated in µamps? I would need about 3.3 amps, would I not? ... As it happens, I do have an old not-working Mac PowerBook from
                          Message 12 of 29 , Feb 14, 2013
                            On Feb 14, 2013, at 12:54 PM, Chris Albertson <albertson.chris@...> wrote:

                            > Only other simple and dirt cheap solution is to buy a 6 volt "wall wort" to
                            > plug-in cube. These will hava a small coaxial power plug and you can fit
                            > your scope with a matching socket. You may have to hunt to find out that
                            > makes the voltage and amps you need cost will be about $20.
                            >
                            Aren't these things usually rated in µamps? I would need about 3.3 amps, would I not?


                            > A hybred solution is tho get a power cube like that but with higher voltage
                            > than you need (buy a 12V suply that is designed for a laptop computer) then
                            > use a simple "reostat" or even the LM317 to drop the volts to some
                            > adjustable level that you set with a knob
                            >
                            > You should not have to build completely from scotch. The bench supply is
                            > a good way to go but costs $100. But you might already own an old PC
                            > notebook power supply and these are very good.

                            As it happens, I do have an old not-working Mac PowerBook from June 2000, but I don't think my wife would like me fooling with that power supply.

                            --
                            Elliot

                            --
                            Elliot Kirschbaum
                            Shepherdstown, WV
                            kingfisher501 at gmail dot com





                            [Non-text portions of this message have been removed]
                          • Elliot Kirschbaum
                            ... I am certainly willing to consider that. -- Elliot -- Elliot Kirschbaum Shepherdstown, WV kingfisher501 at gmail dot com [Non-text portions of this message
                            Message 13 of 29 , Feb 14, 2013
                              On Feb 14, 2013, at 3:45 PM, billbillt_2000 <2222lab@...> wrote:

                              > Looks to me you did the wisest thing converting to LED..

                              I am certainly willing to consider that.

                              --
                              Elliot

                              --
                              Elliot Kirschbaum
                              Shepherdstown, WV
                              kingfisher501 at gmail dot com





                              [Non-text portions of this message have been removed]
                            • J. Forster
                              ... No. they are typically 5 to 50 Watts. A wall wart or old laptop supply would only be the first stage. It would need to be followed by a voltage regulator.
                              Message 14 of 29 , Feb 14, 2013
                                >
                                >> Only other simple and dirt cheap solution is to buy a 6 volt "wall wort"
                                >> to
                                >> plug-in cube. These will hava a small coaxial power plug and you can fit
                                >> your scope with a matching socket. You may have to hunt to find out that
                                >> makes the voltage and amps you need cost will be about $20.
                                >>
                                > Aren't these things usually rated in µamps? I would need about 3.3 amps,
                                > would I not?

                                No. they are typically 5 to 50 Watts.

                                A wall wart or old laptop supply would only be the first stage. It would
                                need to be followed by a voltage regulator.

                                The wall wart would:

                                Need to supply >3.3 A IF you use a linear regulator
                                Need to supply <3.3 A If you use a switching regulator

                                With a linear regulator, the current in is slightly more than the current
                                out.

                                A switching regulator is like a transformer for DC. Power in is only
                                slightly greater than power out. So, a switcher could take in 18VDC @ 1.1A
                                and put out 6VDC @ 3.3A.

                                -John

                                ===================
                              • smoketester
                                The short answer is with a (full-wave) rectifier . ... Couple of observations: If the voltage applied to the bulb socket is 6.5VAC, the full-wave rectified
                                Message 15 of 29 , Mar 20, 2013
                                  The short answer is "with a (full-wave) rectifier".
                                  >
                                  Couple of observations:

                                  If the voltage applied to the bulb socket is 6.5VAC, the full-wave
                                  rectified OUTPUT voltage UNFILTERED calculates to 2.926VDC.
                                  Unfortunately, this output level is useless in most (all?) LED's
                                  given that this is less than the typical forward voltages.

                                  If you want the quick and (not so) dirty solution, consider a
                                  switching power supply (it doesn't require a large transformer
                                  with a beercan size capacitor) and a current limiting device
                                  (pulse width modulator, anybody?)

                                  Don't forget the safety ballast resistor.

                                  Happy motoring,

                                  Smoketester

                                  (Plug it in...See if it smokes)


                                  --- In Microscope@yahoogroups.com, "billbillt_2000" <2222lab@...> wrote:
                                  >
                                  >
                                  > Tony,
                                  > Looks to me you did the wisest thing converting to LED..
                                  > BillT
                                  > --- In Microscope@yahoogroups.com, "Tony" wrote:
                                  > >
                                  > > Ah well, I've given up on bulbs. Here's my newest conversion of my Swift inverted.
                                  > >
                                  > > http://groups.yahoo.com/group/Microscope/photos/album/353933373/pic/231628664/view
                                  > >
                                  > > Tony
                                  > >
                                  > > Reading UK
                                  > >
                                  > > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
                                  > > >
                                  > > > The bulb voltage is of no matter, except that for constant wattage, the
                                  > > > higher voltage bulbs will have shorter thermal time constants, hence
                                  > > > flicker more.
                                  > > >
                                  > > > -John
                                  > > >
                                  > > > =============
                                  > > >
                                  > > >
                                  > > >
                                  > > > > Ok, I thought we were dealing with a 6V bulb.
                                  > > > >
                                  > > > > Tony
                                  > > > >
                                  > > > > --- In Microscope@yahoogroups.com, "J. Forster" wrote:
                                  > > > >>
                                  > > > >> Tony,
                                  > > > >>
                                  > > > >> It's not that simple.
                                  > > > >>
                                  > > > >> If you use a big capacitor, as you correctly suggest, the aim is to
                                  > > > >> charge
                                  > > > >> the cap up to the peak voltage on every half-cycle of line. The cap
                                  > > > >> needs
                                  > > > >> to be big enough that the voltage does not dip much before the next peak
                                  > > > >> comes along.
                                  > > > >>
                                  > > > >> BUT, that means the capacitor stays charged to the full peak of the
                                  > > > >> transformer output, which ius 0.5*SQR2 * RMS of transformer. If trhe
                                  > > > >> transfoirmer secondary is 12 VRMS, the peak will be around 18VDC.
                                  > > > >>
                                  > > > >> The ulb will burn out just about instantly.
                                  > > > >>
                                  > > > >> If you are going to full-wave rectify and use a big filter, you must
                                  > > > >> reduce to transformer output.
                                  > > > >>
                                  > > > >> Please see my previous post for good solutions.
                                  > > > >>
                                  > > > >> -John
                                  > > > >>
                                  > > > >> ===================
                                  > > > >>
                                  > > > >>
                                  > > > >>
                                  > > > >> > Don't forget folks that we're talking about something in the region of
                                  > > > >> 6V
                                  > > > >> > 20W. Which means about 3.3A. It should be possible to use the scope AC
                                  > > > >> > output ( which will probably be around 10V AC off load) into a bridge
                                  > > > >> > rated at say 10A ( be generous they're cheap) and a reservoir cap of
                                  > > > >> > around 47000uF @16V (at least) working will produce very little
                                  > > > >> ripple. (
                                  > > > >> > around 250mv) Remember it's just the lamp filament and not the camera
                                  > > > >> > that's running off this supply.
                                  > > > >> > The problem comes when you want to build it all into the scope, as the
                                  > > > >> cap
                                  > > > >> > tends to be on the tubby side. It is possible to use two or more caps
                                  > > > >> in
                                  > > > >> > parallel which may ease space problems.
                                  > > > >> >
                                  > > > >> > regards
                                  > > > >> >
                                  > > > >> > Tony
                                  > > > >> >
                                  > > > >> > Reading UK
                                  > > > >> >
                                  > > > >> > --- In Microscope@yahoogroups.com, Chris Albertson wrote:
                                  > > > >> >>
                                  > > > >> >> Yes, you can buy a bridge reactifiier like in the data sheet. But
                                  > > > >> four
                                  > > > >> >> diodes will work as well. Cost about 1 to 5 cents each. Then you
                                  > > > >> >> still
                                  > > > >> >> don't have good DC. You need a filter cap and a regulator. And of
                                  > > > >> >> course
                                  > > > >> >> #1 most importance is the transformer.
                                  > > > >> >>
                                  > > > >> >> You can buy a good DC power supply with adjustable voltage for not a
                                  > > > >> lot
                                  > > > >> >> of
                                  > > > >> >> money and you can build them too. The Googe term is "power supply".
                                  > > > >> >> You
                                  > > > >> >> can buy them already build on a circuit borad on eBay for maybe $10.
                                  > > > >> >> Thefirst thing to decide is the range of voltages you need is it 2-6
                                  > > > >> >> volts
                                  > > > >> >> or 5-9 volts or whatever.
                                  > > > >> >>
                                  > > > >> >> There must be many people with enginerring degrees on this list who
                                  > > > >> can
                                  > > > >> >> help but a simple DC power supply is something you can learn to
                                  > > > >> design
                                  > > > >> >> and
                                  > > > >> >> build assuming you know the basics of electronics. I absolutly
                                  > > > >> >> recommend
                                  > > > >> >> a regulated power supply if the goal is ripple fee DC. Those simple
                                  > > > >> >> can
                                  > > > >> >> cheap LM317 regulator chips cost under a buck and will produce nearly
                                  > > > >> >> perfect, clean DC.
                                  > > > >> >>
                                  > > > >> >> You can build or buy but eBay makes buying the better option see item
                                  > > > >> >> number 271153856438
                                  > > > >> >> Look at the above in the product description is a classic schematic
                                  > > > >> that
                                  > > > >> >> shows you how to use that rectifier chip you found. As you can see
                                  > > > >> if
                                  > > > >> >> is
                                  > > > >> >> just the first part of a larger circuit. But you can buy it all for
                                  > > > >> >> $10.
                                  > > > >> >>
                                  > > > >> >>
                                  > > > >> >>
                                  > > > >> >> On Thu, Feb 14, 2013 at 6:23 AM, Elliot Kirschbaum
                                  > > > >> >> wrote:
                                  > > > >> >>
                                  > > > >> >> > **
                                  > > > >> >> >
                                  > > > >> >> >
                                  > > > >> >> > This is a followup to my post on "What Can I Do About Electrical
                                  > > > >> >> > Interference?"
                                  > > > >> >> >
                                  > > > >> >> > Tony gets first prize. I did the experiment he suggested. No
                                  > > > >> >> interference
                                  > > > >> >> > using natural light with the electronics running. Take the mirror
                                  > > > >> away
                                  > > > >> >> so
                                  > > > >> >> > the light is from the lamp and the interference pattern resumes. So
                                  > > > >> >> the
                                  > > > >> >> > interference pattern is generated by the lamp.
                                  > > > >> >> >
                                  > > > >> >> > So what do I do now? Is it simply a matter of putting a diode
                                  > > > >> bridge
                                  > > > >> >> > rectifier and a smoothing capacitor between the transformer and the
                                  > > > >> >> lamp?
                                  > > > >> >> >
                                  > > > >> >> > I have posted a picture of such as circuit in Elliot's Microscope
                                  > > > >> >> folder
                                  > > > >> >> > http://tinyurl.com/abew7op
                                  > > > >> >> >
                                  > > > >> >> > The rectifier in that circuit uses a Toshiba 1B4B42 bridge
                                  > > > >> rectifier.
                                  > > > >> >> The
                                  > > > >> >> > data sheet for which can be found at the following URL
                                  > > > >> >> >
                                  > > > >> >> > http://www.alldatasheet.com/datasheet-pdf/pdf/29740/TOSHIBA/1B4B42.html
                                  > > > >> >> >
                                  > > > >> >> > Will this work to change the 6V AC to 6V DC in my AO 110
                                  > > > >> Illuminator?
                                  > > > >> >> >
                                  > > > >> >> > How big is this thing? Will it fit inside the base?
                                  > > > >> >> >
                                  > > > >> >> > Are the values for C1 and R1 in the circuit what I should use to
                                  > > > >> >> smooth
                                  > > > >> >> > the DC output, even though V1 in my application is 6V rather than
                                  > > > >> 12,
                                  > > > >> >> and
                                  > > > >> >> > it may be at 60Hz rather than 50Hz?
                                  > > > >> >> >
                                  > > > >> >> > Any help, other than telling me to take a college level course in
                                  > > > >> >> > electronics, will be appreciated.
                                  > > > >> >> >
                                  > > > >> >> > --
                                  > > > >> >> > Elliot
                                  > > > >> >> >
                                  > > > >> >> > --
                                  > > > >> >> > Elliot Kirschbaum
                                  > > > >> >> > Shepherdstown, WV
                                  > > > >> >> > kingfisher501 at gmail dot com
                                  > > > >> >> >
                                  > > > >> >> > [Non-text portions of this message have been removed]
                                  > > > >> >> >
                                  > > > >> >> >
                                  > > > >> >> >
                                  > > > >> >>
                                  > > > >> >>
                                  > > > >> >>
                                  > > > >> >> --
                                  > > > >> >>
                                  > > > >> >> Chris Albertson
                                  > > > >> >> Redondo Beach, California
                                  > > > >> >>
                                  > > > >> >>
                                  > > > >> >> [Non-text portions of this message have been removed]
                                  > > > >> >>
                                  > > > >> >
                                  > > > >> >
                                  > > > >> >
                                  > > > >>
                                  > > > >
                                  > > > >
                                  > > > >
                                  > > >
                                  > >
                                  >
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