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Lasers

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  • William Koepp
    Ok guys, i know this is not really a beam topic so i apologize pre-hand. You guys are the most intelligent people in the field of electronics that i know
    Message 1 of 25 , Nov 4, 2011
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      Ok guys, i know this is not really a beam topic so i apologize pre-hand. You guys are the most intelligent people in the field of electronics that i know though. So here it is....

      I am working on my final project of the semester, a Staubli robotics system. I am the leader of my team so i must over see everything and one of these area's is safety. So i have designed a work cell with the fail safe light curtain system on top of a half fence. Now to the real issue, budget is almost none existent(part of the challenge as I take it). i decided on using shielded photo resistors as the light sensors, i need a powerful enough light source to span the 6ft from corner to corner. I thought of just using pointer lasers but realized that those get expensive quick. So is there any other less costly way to provide the light?, such as directing/modding a LED to maybe channel light as a suedo laser? Any help would be much appreciated. Thanks :)
    • Alvaro Barcellos
      Use a laser 5mm from ebay or dealextreme and a inside tube photodiode. 2 cents.
      Message 2 of 25 , Nov 4, 2011
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        Use a laser 5mm from ebay or dealextreme and a "inside tube" photodiode.

        2 cents.

        On Fri, Nov 4, 2011 at 12:57 PM, William Koepp <william.koepp@...> wrote:
         

        Ok guys, i know this is not really a beam topic so i apologize pre-hand. You guys are the most intelligent people in the field of electronics that i know though. So here it is....

        I am working on my final project of the semester, a Staubli robotics system. I am the leader of my team so i must over see everything and one of these area's is safety. So i have designed a work cell with the fail safe light curtain system on top of a half fence. Now to the real issue, budget is almost none existent(part of the challenge as I take it). i decided on using shielded photo resistors as the light sensors, i need a powerful enough light source to span the 6ft from corner to corner. I thought of just using pointer lasers but realized that those get expensive quick. So is there any other less costly way to provide the light?, such as directing/modding a LED to maybe channel light as a suedo laser? Any help would be much appreciated. Thanks :)


      • William Koepp
        I do not want to use a photo diode in the circuit because i need the resistor in there in combo with a transistor and zener diode to create my fail safe, there
        Message 3 of 25 , Nov 4, 2011
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          I do not want to use a photo diode in the circuit because i need the resistor in there in combo with a transistor and zener diode to create my fail safe, there must not be any chance that even the mV from a photo diode could trigger the transistor. im not sure if the college will allow me to buy from ebay or simular, due to risk, but i will throw that idea by them sense the prices are so much lower. 
        • scottallenburns
          My two cents... It all comes down to the ambient light level. If in a dark room, any old LEDs will work as long as the LDR sensors have their signal amplified
          Message 4 of 25 , Nov 4, 2011
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            My two cents... It all comes down to the ambient light level. If in a dark room, any old LEDs will work as long as the LDR sensors have their signal amplified appropriately. But if in a bright environment, you'll need more focused (narrower radiation angle and highter power) LEDs to separate the signal from the ambient light noise.
            Scott

            --- In beam@yahoogroups.com, William Koepp <william.koepp@...> wrote:
            >
            > Ok guys, i know this is not really a beam topic so i�apologize�pre-hand. You guys are the most intelligent people in the field of electronics that i know though. So here it is....
            >
            > I am working on my final project of the semester, a Staubli robotics system. I am the leader of my team so i must over see everything and one of these area's is safety. So i have designed a work cell with the fail safe light�curtain�system on top of a half fence. Now to the real issue, budget is almost none�existent(part of the�challenge�as I take it). i decided on using shielded photo resistors as the light sensors, i need a powerful enough light source to span the 6ft from corner to corner. I thought of just using pointer lasers but realized that those get expensive quick. So is there any other less costly way to provide the light?, such as directing/modding�a LED to maybe channel light as a suedo laser? Any help would be much appreciated. Thanks :)
            >
          • Alvaro Barcellos
            if using a laser beam and a inside dark long tube led, it will works. ... if using a laser beam and a inside dark long tube led, it will works. On Fri, Nov
            Message 5 of 25 , Nov 4, 2011
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              if using a laser beam and a "inside dark long tube" led, it will works.

              On Fri, Nov 4, 2011 at 1:31 PM, scottallenburns <yahoo@...> wrote:
               

              My two cents... It all comes down to the ambient light level. If in a dark room, any old LEDs will work as long as the LDR sensors have their signal amplified appropriately. But if in a bright environment, you'll need more focused (narrower radiation angle and highter power) LEDs to separate the signal from the ambient light noise.
              Scott

              --- In beam@yahoogroups.com, William Koepp <william.koepp@...> wrote:
              >
              > Ok guys, i know this is not really a beam topic so i�apologize�pre-hand. You guys are the most intelligent people in the field of electronics that i know though. So here it is....
              >
              > I am working on my final project of the semester, a Staubli robotics system. I am the leader of my team so i must over see everything and one of these area's is safety. So i have designed a work cell with the fail safe light�curtain�system on top of a half fence. Now to the real issue, budget is almost none�existent(part of the�challenge�as I take it). i decided on using shielded photo resistors as the light sensors, i need a powerful enough light source to span the 6ft from corner to corner. I thought of just using pointer lasers but realized that those get expensive quick. So is there any other less costly way to provide the light?, such as directing/modding�a LED to maybe channel light as a suedo laser? Any help would be much appreciated. Thanks :)
              >


            • William Koepp
              Well i am going to propose the extremedeal site as a buying option, if that is turned down the i suppose i will just try to make lasers using ultra bright leds
              Message 6 of 25 , Nov 4, 2011
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                Well i am going to propose the extremedeal site as a buying option, if that is turned down the i suppose i will just try to make lasers using ultra bright leds and glass cylinders to prevent light refraction.
              • Duane C. Johnson
                Will there be strong ambient light? If so, modulate the LED source at say 1KHz or so. Then sense the presence or absence of the 1KHz on the sensor. Instead of
                Message 7 of 25 , Nov 4, 2011
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                  Will there be strong ambient light?

                  If so, modulate the LED source at say 1KHz or so.
                  Then sense the presence or absence of the 1KHz
                  on the sensor.

                  Instead of a photo conductive diode you might
                  use a pair of green LEDs. One as a light source
                  and the other as a photovoltaic sensor.

                  LEDs work quite nicely as PV sensors.

                  Duane
                • David Buckley
                  The LDR will react to light levels so how can it be failsafe. It will respond to any sufficiently bright light regardless of where it comes from, your
                  Message 8 of 25 , Nov 4, 2011
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                    The LDR will react to light levels so how can it be failsafe. It will respond to any sufficiently bright light regardless of where it comes from, your equipment or not. Encoding a message in the beam could make it failsafe.
                    Laser Pointers are dirt cheap, you can get them here for £1, ie about $1.50.
                    LDRs are not that responsive to Laser Pointers anyway.
                    eBay, what risk if you are buying from a shop?
                     
                    ----- Original Message -----
                    Sent: Friday, November 04, 2011 3:26 PM
                    Subject: Re: [beam] Lasers

                     

                    I do not want to use a photo diode in the circuit because i need the resistor in there in combo with a transistor and zener diode to create my fail safe, there must not be any chance that even the mV from a photo diode could trigger the transistor. im not sure if the college will allow me to buy from ebay or simular, due to risk, but i will throw that idea by them sense the prices are so much lower. 

                  • William Koepp
                    With a photo resistor i have more control over the circuit because i can get it at a min resistance level where i can not have that control with a photo diode.
                    Message 9 of 25 , Nov 4, 2011
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                      With a photo resistor i have more control over the circuit because i can get it at a min resistance level where i can not have that control with a photo diode. the photo resistor as long as it has a very bright light source will keep the transistor "on" which connects to a relay and then to the power supply of the Robotic system. once power is removed and the safe button is released it will require a person to physically push it in before power is returned. power to the sensor also will come from the controller, meaning off stays off. the room is subjected to normal daylight condition's. the photo resistors will also be shielded. the zener diode i mentioned before will be used to also set a voltage level that will have to be maintained. E-bay is considered high risk for several reasons, at least in the colleges eyes. probably due to there are no guaranteed, you buy from a individual not a company, and what you get might not work at all. i am going to propose the other site mentioned before because it is a company and products can be guaranteed.
                    • David Buckley
                      Have you managed to get green LED pairs working over 6 feet? I would love the details, especially for a normally lit room. ... From: Duane C. Johnson To:
                      Message 10 of 25 , Nov 4, 2011
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                        Have you managed to get green LED pairs working over 6 feet? I would love the details, especially for a normally lit room.
                         
                        ----- Original Message -----
                        Sent: Friday, November 04, 2011 4:04 PM
                        Subject: Re: [beam] Re: Lasers

                         

                        Will there be strong ambient light?

                        If so, modulate the LED source at say 1KHz or so.
                        Then sense the presence or absence of the 1KHz
                        on the sensor.

                        Instead of a photo conductive diode you might
                        use a pair of green LEDs. One as a light source
                        and the other as a photovoltaic sensor.

                        LEDs work quite nicely as PV sensors.

                        Duane

                      • David Buckley
                        You can t make lasers like that. ... From: William Koepp To: beam@yahoogroups.com Sent: Friday, November 04, 2011 3:56 PM Subject: [beam] Re: Lasers Well i am
                        Message 11 of 25 , Nov 4, 2011
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                          You can't make lasers like that.
                           
                          ----- Original Message -----
                          Sent: Friday, November 04, 2011 3:56 PM
                          Subject: [beam] Re: Lasers

                           

                          Well i am going to propose the extremedeal site as a buying option, if that is turned down the i suppose i will just try to make lasers using ultra bright leds and glass cylinders to prevent light refraction.

                        • David Buckley
                          The circuit might be failsafe but that doesn t mean the curtain is safe. Shine a light at the sensor and walk through. It is a waste of time being worried
                          Message 12 of 25 , Nov 4, 2011
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                            The circuit might be failsafe but that doesn't mean the curtain is safe. Shine a light at the sensor and walk through.
                            It is a waste of time being worried about a guarantee on a $1.50 item, you spend more trying to get your money back.
                             
                            ----- Original Message -----
                            Sent: Friday, November 04, 2011 4:50 PM
                            Subject: Re: [beam] Lasers

                             

                            With a photo resistor i have more control over the circuit because i can get it at a min resistance level where i can not have that control with a photo diode. the photo resistor as long as it has a very bright light source will keep the transistor "on" which connects to a relay and then to the power supply of the Robotic system. once power is removed and the safe button is released it will require a person to physically push it in before power is returned. power to the sensor also will come from the controller, meaning off stays off. the room is subjected to normal daylight condition's. the photo resistors will also be shielded. the zener diode i mentioned before will be used to also set a voltage level that will have to be maintained. E-bay is considered high risk for several reasons, at least in the colleges eyes. probably due to there are no guaranteed, you buy from a individual not a company, and what you get might not work at all. i am going to propose the other site mentioned before because it is a company and products can be guaranteed.

                          • William Koepp
                            Mr. Buckley  there is no fail safe to definition of your standards. If some one wants that bad to get past one they will. If someone is willing to purposely
                            Message 13 of 25 , Nov 4, 2011
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                              Mr. Buckley  there is no fail safe to definition of your standards. If some one wants that bad to get past one they will. If someone is willing to purposely try to by-pass the light curtian by pointing a light into the sensor then they deserve to have there arm ripped off. And if you look to the designs of say a ruby laser or semiconductor laser then you will see that a laser is just a light source placed within a semi reflective area creating an amplification before the light can pass through the output usually has a source to reduce the refraction of the light and keep it concentrated. We have though im afraid drifted off the topic at hand and this has now come to a dead end. thank you anyway for the help. 
                            • David Buckley
                              ... My opinion exactly. However in a real safety curtain it is something to be taken into consideration, so is a stray sunlight reflection. I do know what a
                              Message 14 of 25 , Nov 4, 2011
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                                > If some one wants that bad to get past one they will. If someone is
                                willing to purposely try to by-pass the light curtain by pointing a light into the sensor then they deserve to have there arm ripped off.
                                My opinion exactly.
                                However in a real safety curtain it is something to be taken into consideration, so is a stray sunlight reflection.
                                 
                                I do know what a laser is and what you propose isn't practically possible, it is silly to mislead people so.
                                 
                                 
                                ----- Original Message -----
                                Sent: Friday, November 04, 2011 9:55 PM
                                Subject: Re: [beam] Lasers

                                 

                                Mr. Buckley  there is no fail safe to definition of your standards. If some one wants that bad to get past one they will. If someone is willing to purposely try to by-pass the light curtian by pointing a light into the sensor then they deserve to have there arm ripped off. And if you look to the designs of say a ruby laser or semiconductor laser then you will see that a laser is just a light source placed within a semi reflective area creating an amplification before the light can pass through the output usually has a source to reduce the refraction of the light and keep it concentrated. We have though im afraid drifted off the topic at hand and this has now come to a dead end. thank you anyway for the help. 

                              • Randy M. Dumse
                                William Koepp said: Friday, November 04, 2011 4:55 PM ... Your original post said Any help would be much appreciated. DAvid was giving you very sound advice.
                                Message 15 of 25 , Nov 5, 2011
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                                  William Koepp said: Friday, November 04, 2011 4:55 PM
                                  > Mr. Buckley there is no fail safe to
                                  > definition of your standards.

                                  Your original post said "Any help would be much appreciated."
                                  DAvid was giving you very sound advice. There is "a fail safe of
                                  his definition". Many systems use encoding on a beam to help
                                  detect the beam from being swamped by ambient.

                                  Do you know what a DC Blocking cap is? Rather than try to detect
                                  the presence or absense of light, (which shows up as a higher or
                                  lower DC level) most break-beams try to detect the presence or
                                  absense of an encoded frequency put ontop of the beam. Putting
                                  that signal on the beam is called Modulation. A photo cell that
                                  detects levels can be tricked by any additional source of light.
                                  However, if you put a DC blocking capacitor in line with the
                                  signal, no matter if there's a little steady ambient light, or a
                                  lot of steady ambient light, the output of the cap is 0V. DC
                                  does not pass through a cap. However, if the signal is modulated
                                  with a higher frequency, the signal appears at the output of the
                                  cap, because caps pass the AC component riding on a DC signal
                                  level, while blocking the DC from passing.

                                  So if you look for that frequency at the output, you know your
                                  transmitter is what is being seen, rather than some unmodulated
                                  source, like a laser pointer or flashlight. Yes someone can try
                                  to match your frequency, and maybe then get past the saftey
                                  curtain, but it won't be casually by accident.

                                  Do I know what I'm talking about? Yes. I've made a commercial
                                  laser break-beam that operates over 1/4 mile separation under
                                  all sort of harsh conditions. It is the beam of a laser for a
                                  barrel-racing timer. I put a high frequency on the beam, so high
                                  most sources like an IR remote control, cannot simulate it. Then
                                  I put a second secret modulation on it almost no one can see
                                  unless they know it is there. I used phase lock loops to recover
                                  both. I know when there's something in the beam, even when the
                                  eye is looking almost right into the sun. Turns out the first
                                  encoding was secure enough, so the second was not necessary in
                                  production.

                                  You might want to offer Mr. Buckley an appology for trying to
                                  tell you something important, which you had promised to be "much
                                  appreciaed", but instead was blown off.

                                  Here's a suggestion. Look at the IS471F. It is used often as a
                                  proximity detector. It modulates an external LED (which could be
                                  a laser) and looks for its own modulation on the reflection to
                                  know if something is in front of it a few inches. However, you
                                  could separate the detector and run wires to the transmitting
                                  LED, and so, look straight down the beam without bouncing it off
                                  anything, and get the range you need, and much greater if you
                                  used a concentrating lenses on both ends. I've done this with a
                                  visible laser and a similar part, the S6986, to retroreflective
                                  material, and had it work reliably over 3 meters separation.
                                  Remember that's out and back. It would go much further without
                                  having to reflect off of a material.

                                  Here's an article on making an IRPD.
                                  http://www.instructables.com/id/A-very-simple-proximity-detector
                                  /?ALLSTEPS

                                  Randy
                                • William Koepp
                                  Mr. Buckley I do apologize for my mood. The way i came off was not intended, i am just stressed with this project. Mr Dumse a encoded signal was my original
                                  Message 16 of 25 , Nov 6, 2011
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                                    Mr. Buckley I do apologize for my mood. The way i came off was not intended, i am just stressed with this project. Mr Dumse a encoded signal was my original thought but unfortunately i am unable to do that at this point. I do greatly appreciate everyone that did comment and help. All of you guys are intelligent and experienced and that is why i come to y'all. I have decided to go with lasers and will just have to cut back somewhere else on the project, as things progress in the project i will update y'all if you like and any future comments i will be more welcoming of and less apprehensive.  
                                  • William
                                    To add on to the below statement, when i said unfortunately i am unable to do that at this point about encoding i was referring to that i am unable to use
                                    Message 17 of 25 , Nov 6, 2011
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                                      To add on to the below statement, when i said "unfortunately i am unable to do that at this point" about encoding i was referring to that i am unable to use anything like a microcontroller or PLC at the time. I am defiantly going to see if i can work in that idea some way of using the cap.

                                      --- In beam@yahoogroups.com, William Koepp <william.koepp@...> wrote:
                                      >
                                      > Mr. Buckley I do apologize for my mood. The way i came off was not intended, i am just stressed with this project. Mr Dumse a encoded signal was my original thought but unfortunately i am unable to do that at this point. I do greatly appreciate everyone that did comment and help. All of you guys are intelligent and experienced and that is why i come to y'all. I have decided to go with lasers and will just have to cut back somewhere else on the project, as things progress in the project i will update y'all if you like and any future comments i will be more welcoming of and less apprehensive.  
                                      >
                                    • David Buckley
                                      That is what projects do, they stress us! Nothing is ever perfect either but if we are aware of problem areas we can at least address them in manuals etc or
                                      Message 18 of 25 , Nov 6, 2011
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                                        That is what projects do, they stress us!
                                        Nothing is ever perfect either but if we are aware of problem areas we can at least address them in manuals etc or for a project explain that in real life such a problem would have to be addressed.
                                        I think if it was me I would use a tightly directed beam (shone down a tube) of 38KHz IR and use a 38KHz receiver (eg TSOP4838). Almost foolproof.
                                        Cheaper and better than using lasers. All you need is a 50c micro to generate the 38KHz (eg a PicAxe08 makes that very easy to do), an IR LED, resistor and a TSOP4838.
                                        DAvid
                                         
                                         
                                        ----- Original Message -----
                                        Sent: Monday, November 07, 2011 1:57 AM
                                        Subject: RE: [beam] Lasers

                                         

                                        Mr. Buckley I do apologize for my mood. The way i came off was not intended, i am just stressed with this project. Mr Dumse a encoded signal was my original thought but unfortunately i am unable to do that at this point. I do greatly appreciate everyone that did comment and help. All of you guys are intelligent and experienced and that is why i come to y'all. I have decided to go with lasers and will just have to cut back somewhere else on the project, as things progress in the project i will update y'all if you like and any future comments i will be more welcoming of and less apprehensive.  
                                        < /div>

                                      • David Buckley
                                        I think when you say unable to use anything like a microcontroller or PLC you are sort of mixing things up and making life difficult. A PLC generally is a
                                        Message 19 of 25 , Nov 6, 2011
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                                          I think when you say unable to use anything like a microcontroller or PLC  you are sort of  mixing things up and making life difficult.
                                          A PLC generally is a box of electronics and never cheap.
                                          A microcontroller on the other hand is just a chip and (if you choose the right one) is as cheap and as hard to use as an LED.
                                          Whereas one time you might have used a 555 timer (for example to generate a 38KHz signal) it is now easier to use a microcontroller chip.
                                          And since this is Beam, you should understand freeforming so you wouldn't even need a PCB.
                                           
                                           
                                          ----- Original Message -----
                                          From: William
                                          Sent: Monday, November 07, 2011 2:10 AM
                                          Subject: [beam] Re: Lasers

                                           

                                          To add on to the below statement, when i said "unfortunately i am unable to do that at this point" about encoding i was referring to that i am unable to use anything like a microcontroller or PLC at the time. I am defiantly going to see if i can work in that idea some way of using the cap.

                                          --- In beam@yahoogroups.com, William Koepp <william.koepp@...> wrote:
                                          >
                                          > Mr. Buckley I do apologize for my mood. The way i came off was not intended, i am just stressed with this project. Mr Dumse a encoded signal was my original thought but unfortunately i am unable to do that at this point. I do greatly appreciate everyone that did comment and help. All of you guys are intelligent and experienced and that is why i come to y'all. I have decided to go with lasers and will just have to cut back somewhere else on the project, as things progress in the project i will update y'all if you like and any future comments i will be more welcoming of and less apprehensive.  
                                          >

                                        • William Koepp
                                          Yes i am unable to use micro s. For some reason my professor seems against them and is all big on PLC s, especially Siemens made ones. I am unable though to
                                          Message 20 of 25 , Nov 6, 2011
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                                            Yes i am unable to use micro's. For some reason my professor seems against them and is all big on PLC's, especially Siemens made ones. I am unable though to use a PLC because we have none to spare and as you said they are costly. I am really going to try and push the topic of using microcontrollers for this do to the added safety it can provide. I have yet to work with any true PLCs myself, so in your experience would it be easy to wire a PLC to the picaxes if i am able to go with those? We will eventually add a PLC into the system. To the freeforming, well i am ok but far from great, we have some perf/proto board on hand i think so i might as well use it.  
                                          • David Buckley
                                            Seems as if your professor is living in the last century or at least fondly imagining that he is teaching you the way industry does it, Buy some equipment,
                                            Message 21 of 25 , Nov 6, 2011
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                                              Seems as if your professor is living in the last century or at least fondly imagining that he is teaching you the way 'industry' does it, Buy some equipment, wire it together and hey presto you have your system. In that case instead of designing a light curtain he should be insisting you obtain items off the shelf to create your curtain.
                                               
                                              Why would you wan to wire a PLC to a PicAxe? See later.
                                               
                                              I suggested you generate a 38KHz signal to drive an IR-LED, you can't (or at least you couldn't) do that with a PLC. In the past you would have used a 555 timer IC or similar to generate the signal which would of course depend on the stability of the resistors and capacitors used.
                                              Nowadays it is easier to use a singlechip microcontroller with an inbuilt oscillator and program a pin to output a 38KHz signal.
                                              I mentioned a PicAxe because they are easy to program and generating 38KHz output and signals to Sony codes is built into the language and they don't need a programmer because they have a bootloader. You could do the same with other small PICs or AVRs but maybe need to get programmers and compilers. Reinventing wheels is costly in terms of time at least. And if you are making a one-off who cares if the parts cost is 10c or 50c. Having generated your 38KHz IR beam a 38KHz detector IC would do all the work giving you a low for signal present and high for no signal. You could feed that signal into whatever latching circuit you want to use. It would be the output from that circuit you would feed to the PLC. Now the latch maybe another small microcontroller that is looking for codes in the IR stream for added safety. Again the PicAxe chips have that functionality (for Sony codes) built into the language.
                                              It depends on the PLC you use what logic levels it can read.
                                              You need to understand PLCs because that is what industry uses, they are very rugged and virtually bomb proof but it is horses for courses, you wouldn't try and clean your teeth with a yard brush.
                                              DAvid
                                               
                                               
                                              ----- Original Message -----
                                              Sent: Monday, November 07, 2011 3:59 AM
                                              Subject: Re: [beam] Re: Lasers

                                               

                                              Yes i am unable to use micro's. For some reason my professor seems against them and is all big on PLC's, especially Siemens made ones. I am unable though to use a PLC because we have none to spare and as you said they are costly. I am really going to try and push the topic of using microcontrollers for this do to the added safety it can provide. I have yet to work with any true PLCs myself, so in your experience would it be easy to wire a PLC to the picaxes if i am able to go with those? We will eventually add a PLC into the system. To the freeforming, well i am ok but far from great, we have some perf/proto board on hand i think so i might as well use it.  

                                            • William Koepp
                                              Hahaha yeah he does do the when i was in the industry... alot. The reason i asked is because he wants to get rid of the adept controller it has and wire it
                                              Message 22 of 25 , Nov 6, 2011
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                                                Hahaha yeah he does do the "when i was in the industry..." alot. The reason i asked is because he wants to get rid of the adept controller it has and wire it to a PLC sometime next year, which i dont understand because we are about to put a brand new $4k DEPS board into the controller. I just try to do as he asks and keep a good GPA. I will be taking a PLC course but it is not for another two semesters i believe.
                                              • Randy M. Dumse
                                                William said: Sunday, November 06, 2011 8:10 PM ... Maybe I m too long winded in my replies. Seems you ve missed my point. Let me make it simple. Get an IS471F
                                                Message 23 of 25 , Nov 7, 2011
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                                                  William said: Sunday, November 06, 2011 8:10 PM
                                                  > When i said "unfortunately i am unable to do that
                                                  > at this point" about encoding i was referring to
                                                  > that i am unable to use anything like a
                                                  > microcontroller or PLC at the time. ...
                                                  > I am defiantly going to see if i can work
                                                  > in that idea some way of using the cap.

                                                  Maybe I'm too long winded in my replies. Seems you've missed my
                                                  point.

                                                  Let me make it simple.

                                                  Get an IS471F and a matching IR LED. Put the IS471F on one side
                                                  of the opening. Put the IR LED (via wires run on the floor or
                                                  elsewise) on the other side.

                                                  You can get ~9" detection doing this as an IRPD, but straight
                                                  on, as a break-beam it might go quite a bit further. Then you
                                                  have your encoding, already built in. The IS471F provides the
                                                  drive to the LED, and that drive is encoded. Then inside the
                                                  IS471F is the whole circuit that checks incoming IR light for
                                                  that encoding. Very simple. Very cheap.

                                                  http://www.junun.org/MarkIII/Info.jsp?item=46 $2.50
                                                  http://www.junun.org/MarkIII/Info.jsp?item=47 $2.50

                                                  If you don't get the range you want (testing is called "an
                                                  experiment", useful in your learning) you can extend it by
                                                  putting the LED and the detector at the focal point of a lens.
                                                  Probably cheaper, you could use a laser for the IR LED. Or use
                                                  the similar S6986, and use a visible laser. Only a little more
                                                  expensive, but is much easier to get lined up.

                                                  http://www.junun.org/MarkIII/Info.jsp?item=79 $4.00
                                                  http://www.dealextreme.com/p/6mm-5mw-red-laser-module-3-5-4-5v-1
                                                  3378 $1.60

                                                  There's your whole project. Output is a open collector to GND to
                                                  signal something in the beam.

                                                  Randy
                                                • William Koepp
                                                  Thank you Randy for the idea. I am going to try to use a Picaxe or 555 timer though. we have the 555 s on hand. Yes i think your reply hand gone a bit over my
                                                  Message 24 of 25 , Nov 7, 2011
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                                                    Thank you Randy for the idea. I am going to try to use a Picaxe or 555 timer though. we have the 555's on hand. Yes i think your reply hand gone a bit over my head, and if i tried to explain it to the others, who have even less understanding of electronics, it would def go right over there head. I will keep your idea's in mind though because situations are constantly changing. I have my proposal in about 30mins, so i will find out what is excepted and what is not.

                                                  • Alvaro Barcellos
                                                    If you put a DC blocking capacitor in line with the signal, no matter if there s a little steady ambient light, or a lot of steady ambient light, the output
                                                    Message 25 of 25 , Nov 7, 2011
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                                                      " If you put a DC blocking capacitor in line with the
                                                      signal, no matter if there's a little steady ambient light, or a
                                                      lot of steady ambient light, the output of the cap is 0V. DC
                                                      does not pass through a cap. However, if the signal is modulated
                                                      with a higher frequency, the signal appears at the output of the
                                                      cap, because caps pass the AC component riding on a DC signal
                                                      level, while blocking the DC from passing. "

                                                      A basic lesson.

                                                      use simply solutions, a capacitor, a crystal (32.768 kHz) or ressonator (445kHz) and a watch-dog.


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