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Fwd: [UKHAS] Launch annoucement, Gliwice, Polnad sat, 28 sep 2013 9:00 UTC

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  • Anthony Stirk
    Forwarded as HF may make it to the US. Regards, Anthony M0UPU ... From: SP9UOB Date: Wed, Sep 25, 2013 at 10:51 AM Subject: [UKHAS] Launch
    Message 1 of 21 , Sep 25, 2013
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      Forwarded as HF may make it to the US.

      Regards,

      Anthony M0UPU

      ---------- Forwarded message ----------
      From: SP9UOB <verox75@...>
      Date: Wed, Sep 25, 2013 at 10:51 AM
      Subject: [UKHAS] Launch annoucement, Gliwice, Polnad sat, 28 sep 2013 9:00 UTC
      To: ukhas@...


      Hi,

      On Saturday we are planning on launching three balloons from Gliwice Glider Airport.

      - First launch, which may be cancelled because of bad predictions: http://predict.habhub.org/#!/uuid=2442a26e2799eb83f824b548ffa1733f1c80c6ea (we dont want to lose our precious equipment in mountains), winn be carring:

       SEBA-4 at 9:00 UTC

       - APRS tracker 300 mW SP9UOB-11 QRG 144.800 MHz
       - DominoEX11 tracker on HF 1Watt output QRG 21.401 MHz USB (Dial freq 21.400 MHz) transmission every minute (disabled during WSPR transmission)
       - CW (Morse) id - callsign, locator and altitude every 5 minutes
       - WSPR on 21.096100 MHz - two transmissions (6 digit locator) every 12 minutes
       - ATV on 23 cm and 6 cm

      Any listeners on HF (especially US and UK) are welcome.

      - Second launch - from stsproject.net at 10:00 UTC
      • STS-8, QRG 438.090 MHz, USB, UKHAS RTTY 300 Bd, 7N2, 450 Hz shift
      • STS-8N, QRG 438.020 MHz, USB, UKHAS RTTY 300 Bd, 7N2, 450 Hz shift

      - and third launch (very high altitude attempt) 

       SEBA-5 at 11:00 UTC

         QRG 437.600 MHz USB, RTTY 50 baud, 7n2 470 Hz shift.


      73! Tom SP9UOB





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    • Michael Hojnowski
      Hiya, I ve got a microcontroller and radio set up to send aloft on a balloon. We hope to let it go for an hour or so, and have it cut itself down, and then
      Message 2 of 21 , Sep 26, 2013
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        Hiya,

        I've got a microcontroller and radio set up to send aloft on a balloon.
        We hope to let it go for an hour or so, and have it cut itself down, and
        then foxhunt the transmitter.

        I tried using a pair of mosfets in parallel between the microcontroller
        and the nichrome we want to use for cut-down, but the mosfets heat up,
        and the nichrome doesn't. I'm more of a software guy than a hardware
        one. What have people been using for switching their cutdown wires?

        Thanks for any suggestions!
        Mike
        KD2EAT
      • L. Paul Verhage
        Relays. They need more current to close, but don t have the voltage drop. The relay is closed for such a short time that its current draw is insignificant.
        Message 3 of 21 , Sep 26, 2013
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          Relays. They need more current to close, but don't have the voltage drop. The relay is closed for such a short time that its current draw is insignificant.

          Paul

          On Sep 26, 2013 8:34 PM, "Michael Hojnowski" <kd2eat@...> wrote:
          Hiya,

          I've got a microcontroller and radio set up to send aloft on a balloon.
          We hope to let it go for an hour or so, and have it cut itself down, and
          then foxhunt the transmitter.

          I tried using a pair of mosfets in parallel between the microcontroller
          and the nichrome we want to use for cut-down, but the mosfets heat up,
          and the nichrome doesn't.  I'm more of a software guy than a hardware
          one.  What have people been using for switching their cutdown wires?

          Thanks for any suggestions!
          Mike
          KD2EAT


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        • Mike Manes
          Hi Mike, EOSS uses a 5A relay to close the burner ckt thru a short (1m) run of #16-2 zip cord from 3S CR123 LiSO2 cells which are separate from the controller
          Message 4 of 21 , Sep 26, 2013
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            Hi Mike,

            EOSS uses a 5A relay to close the burner ckt thru a short
            (1m) run of #16-2 zip cord from 3S CR123 LiSO2 cells which
            are separate from the controller Vcc supply. The relay is
            closed for 10s and the cord burns in about 4s. The burner
            is 1.5 ohms of NiCr wound tight over the cord and inside
            a styrofoam box with 1/2" walls.

            Sounds as though your MOSFETS have too high Rds-on. The burner
            current can exceed 5A, so get a FET with no more than 40 milliohm
            Rds-on to keep Pj < 1W. Or use a relay.

            GL on ur flight & happy hunting!
            73 de Mike W5VSI

            On 9/26/13 8:34 PM, Michael Hojnowski wrote:
            > Hiya,
            >
            > I've got a microcontroller and radio set up to send aloft on a balloon.
            > We hope to let it go for an hour or so, and have it cut itself down, and
            > then foxhunt the transmitter.
            >
            > I tried using a pair of mosfets in parallel between the microcontroller
            > and the nichrome we want to use for cut-down, but the mosfets heat up,
            > and the nichrome doesn't. I'm more of a software guy than a hardware
            > one. What have people been using for switching their cutdown wires?
            >
            > Thanks for any suggestions!
            > Mike
            > KD2EAT
            >
            >
            > ------------------------------------
            >
            > Yahoo! Groups Links
            >
            >
            >
          • Michael Hojnowski
            Thanks for the tips. Again, I m a rookie with hardware. I m poking around radioshack.com, and see 5A relays, but they look HUGE. We re trying to keep the
            Message 5 of 21 , Sep 26, 2013
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              Thanks for the tips. Again, I'm a rookie with hardware. I'm poking
              around radioshack.com, and see 5A relays, but they look HUGE. We're
              trying to keep the payload light. Can you perhaps share pointers to the
              relays you're using? Perhaps I'm not using the right search terms, and
              coming up with the wrong stuff. Our system is presently powered by a
              3.7v LiPo battery, which runs our radio and controller. It's got enough
              milliamp hours to do that and light up the nichrome. Ideally, we'd have
              a relay which we could trip from the microcontroller (or via the
              mosfets), at 3.7v, and shunt enough power through to do the job without
              having to also add more batteries to the payload. We're doing this with
              a cluster of mylar balloons, and (presently) a 73 gram payload.

              Mike
              KD2EAT

              On 9/26/2013 10:48 PM, Mike Manes wrote:
              >
              > EOSS uses a 5A relay to close the burner ckt thru a short
              > (1m) run of #16-2 zip cord from 3S CR123 LiSO2 cells which
              > are separate from the controller Vcc supply. The relay is
              > closed for 10s and the cord burns in about 4s. The burner
              > is 1.5 ohms of NiCr wound tight over the cord and inside
              > a styrofoam box with 1/2" walls.
            • Mike Manes
              Hi Mike, The problem with low Rds-on FETs in a 3.7V system is getting Vgs high enough to saturate the channel. So a relay is the simplest solution. Here s what
              Message 6 of 21 , Sep 26, 2013
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                Hi Mike,

                The problem with low Rds-on FETs in a 3.7V system is getting Vgs high
                enough to saturate the channel. So a relay is the simplest solution.
                Here's what I found at DigiKey:

                http://www.digikey.com/product-search/en?pv72=5&pv1409=32&pv1410=26&FV=fff40010%2Cfff80367&k=relay&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

                3V 67mA coils are easy enough to drive using a 2N7000 or 2N3904 from
                a uC output pin, but be SURE to add a snubber diode around the coil
                to trap the turnoff current! Less than $6, but DigiKey may have a
                min order or surcharge. If so, try Jameco & Sparkfun. Yeah, more
                mass than the FET, but it'll git 'er done.

                73 de Mike W5VSI

                On 9/26/13 9:07 PM, Michael Hojnowski wrote:
                > Thanks for the tips. Again, I'm a rookie with hardware. I'm poking
                > around radioshack.com, and see 5A relays, but they look HUGE. We're
                > trying to keep the payload light. Can you perhaps share pointers to the
                > relays you're using? Perhaps I'm not using the right search terms, and
                > coming up with the wrong stuff. Our system is presently powered by a
                > 3.7v LiPo battery, which runs our radio and controller. It's got enough
                > milliamp hours to do that and light up the nichrome. Ideally, we'd have
                > a relay which we could trip from the microcontroller (or via the
                > mosfets), at 3.7v, and shunt enough power through to do the job without
                > having to also add more batteries to the payload. We're doing this with
                > a cluster of mylar balloons, and (presently) a 73 gram payload.
                >
                > Mike
                > KD2EAT
                >
                > On 9/26/2013 10:48 PM, Mike Manes wrote:
                >>
                >> EOSS uses a 5A relay to close the burner ckt thru a short
                >> (1m) run of #16-2 zip cord from 3S CR123 LiSO2 cells which
                >> are separate from the controller Vcc supply. The relay is
                >> closed for 10s and the cord burns in about 4s. The burner
                >> is 1.5 ohms of NiCr wound tight over the cord and inside
                >> a styrofoam box with 1/2" walls.
                >
                >
                >
                > ------------------------------------
                >
                > Yahoo! Groups Links
                >
                >
                >
              • HarryM
                I use one dual channel MosFet, 10 turns of small nichrome wrapped around a toothpick (my load line is that size) and 2-9v alkaline batteries in parallel. A
                Message 7 of 21 , Sep 26, 2013
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                  I use one dual channel MosFet, 10 turns of small nichrome wrapped around
                  a toothpick (my load line is that size) and 2-9v alkaline batteries in parallel.
                  A timer is activated by a DTMF decoder and the nichrome is heated for 10 sec.
                   
                  73 Harry KC5TRB
                   
                   
                  What have people been using for switching their cutdown wires?
                • HarryM
                  BTW – My whole cutdown controller (less the burner) is about 1.5”x1.5”. Harry KC5TRB BTW – My whole cutdown controller (less the burner) is about
                  Message 8 of 21 , Sep 26, 2013
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                    BTW – My whole cutdown controller (less the burner) is about 1.5”x1.5”.
                     
                    Harry KC5TRB
                  • Anthony Stirk
                    How thick is the Nichrome ? A beefy FET is fine for cutting down (a low value resistor works well too). Here is a circuit we used,A separate battery pack is
                    Message 9 of 21 , Sep 26, 2013
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                    • 64 KB
                    How thick is the Nichrome ? A beefy FET is fine for cutting down (a low value resistor works well too).

                    Here is a circuit we used,A separate battery pack is used for the cut down.

                    Cheers,

                    Anthony M0UPU


                    On Fri, Sep 27, 2013 at 3:34 AM, Michael Hojnowski <kd2eat@...> wrote:
                     

                    Hiya,

                    I've got a microcontroller and radio set up to send aloft on a balloon.
                    We hope to let it go for an hour or so, and have it cut itself down, and
                    then foxhunt the transmitter.

                    I tried using a pair of mosfets in parallel between the microcontroller
                    and the nichrome we want to use for cut-down, but the mosfets heat up,
                    and the nichrome doesn't. I'm more of a software guy than a hardware
                    one. What have people been using for switching their cutdown wires?

                    Thanks for any suggestions!
                    Mike
                    KD2EAT


                  • David Akerman
                    MOSFETs are just fine so long as you choose one with a suitably low Vgs. I use the IRLB8721 which works from 3.3V logic, has a very low on resistance, costs
                    Message 10 of 21 , Sep 27, 2013
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                      MOSFETs are just fine so long as you choose one with a suitably low Vgs.  I use the IRLB8721 which works from 3.3V logic, has a very low on resistance, costs about $1, and has way more current capability than you'll ever need for this.

                      Dave
                    • Michael Hojnowski
                      Wow, Thanks to everyone who jumped on this and shared information! :-) This is a great forum! It looks like we blew it in terms of mosfet selection. We
                      Message 11 of 21 , Sep 27, 2013
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                        Wow,

                        Thanks to everyone who jumped on this and shared information!  :-)   This is a great forum!

                        It looks like we blew it in terms of mosfet selection.  We bought BS170G's http://www.onsemi.com/pub_link/Collateral/BS170-D.PDF.  The suggestions here are to keep the Rds under 40 uOhms, but these suckers are 5.0 Ohms.  Oops!

                        I'm thinking the shortest path to victory, and lightest solution given our starting point, will be to go with Dave's suggestion below.  That should just plug-replace on my circuit board.

                        This is our first balloon launch, though we have grand plans for APRS, SSTV and such down the road.  We're really just getting started, so this kind of information is really helpful.  Thanks so much!

                        Here's a link to our current (and VERY modest) balloon design.  Try not to laugh.  We're just getting started!  ;-)  http://w2cxm.org/projects/balloon/balloonmark1   (and yes, I really DO solder THAT badly!)

                        Mike
                        KD2EAT

                         

                        On 9/27/2013 4:45 AM, David Akerman wrote:
                         
                        MOSFETs are just fine so long as you choose one with a suitably low Vgs.  I use the IRLB8721 which works from 3.3V logic, has a very low on resistance, costs about $1, and has way more current capability than you'll ever need for this.

                        Dave

                      • Mike Manes
                        Be careful to look deeper into the specs than just Rds-on. Most feature-level specs show Rds-on for a saturated condition, where the Vgs is well over +3V -
                        Message 12 of 21 , Sep 27, 2013
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                          Be careful to look deeper into the specs than just Rds-on. Most
                          feature-level specs show Rds-on for a saturated condition, where the
                          Vgs is well over +3V - often as high as 10-15V. And you won't find
                          any FET that has a 40 micro(u)-ohm spec, but there are plenty lower
                          than 40 milli(m)-ohm - again at Vgs well over 3v. This is why I
                          ended up with a relay.

                          BTW, the BS170/D is a pretty low-power FET: TO-92 with IGSmax of just
                          500 mA. OK to fire a pyro, but one needs like 10X that current for
                          a NiCr nylon lift cord burner.

                          73 de Mike W5VSI

                          On 9/27/13 8:32 AM, Michael Hojnowski wrote:
                          >
                          >
                          > Wow,
                          >
                          > Thanks to everyone who jumped on this and shared information! :-) This
                          > is a great forum!
                          >
                          > It looks like we blew it in terms of mosfet selection. We bought
                          > BS170G's http://www.onsemi.com/pub_link/Collateral/BS170-D.PDF. The
                          > suggestions here are to keep the Rds under 40 uOhms, but these suckers
                          > are 5.0 Ohms. Oops!
                          >
                          > I'm thinking the shortest path to victory, and lightest solution given
                          > our starting point, will be to go with Dave's suggestion below. That
                          > should just plug-replace on my circuit board.
                          >
                          > This is our first balloon launch, though we have grand plans for APRS,
                          > SSTV and such down the road. We're really just getting started, so this
                          > kind of information is really helpful. Thanks so much!
                          >
                          > Here's a link to our current (and VERY modest) balloon design. Try not
                          > to laugh. We're just getting started! ;-)
                          > http://w2cxm.org/projects/balloon/balloonmark1 (and yes, I really DO
                          > solder THAT badly!)
                          >
                          > Mike
                          > KD2EAT
                          >
                          >
                          >
                          > On 9/27/2013 4:45 AM, David Akerman wrote:
                          >> MOSFETs are just fine so long as you choose one with a suitably low
                          >> Vgs. I use the IRLB8721 which works from 3.3V logic, has a very low
                          >> on resistance, costs about $1, and has way more current capability
                          >> than you'll ever need for this.
                          >>
                          >> Dave
                          >
                          >
                          >
                          >
                        • wb8elk
                          Relays would be an option for a more traditional ARHAB payload, but as I understand it they are flying with multiple foil party balloons so every additional
                          Message 13 of 21 , Sep 27, 2013
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                            Relays would be an option for a more traditional ARHAB payload, but as I understand it they are flying with multiple foil party balloons so every additional gram of weight is an issue in this case since you can't fill a foil balloon completely up at launch unless you want a short and low altitude flight (I tried this a few weeks ago and reached 4300 meters (14,107 feet). Even a small relay would add significant weight to their payload in comparison to an SMT FET.
                             
                            - Bill WB8ELK
                             
                             
                             
                             
                            -----Original Message-----
                            From: L. Paul Verhage <nearsys@...>
                            To: GPSL <GPSL@yahoogroups.com>
                            Sent: Fri, Sep 27, 2013 12:16 pm
                            Subject: Re: [GPSL] Seeking advice on nichrome cut-down from microcontroller

                             
                            Relays. They need more current to close, but don't have the voltage drop. The relay is closed for such a short time that its current draw is insignificant.
                            Paul
                            On Sep 26, 2013 8:34 PM, "Michael Hojnowski" <kd2eat@...> wrote:
                            Hiya,

                            I've got a microcontroller and radio set up to send aloft on a balloon.
                            We hope to let it go for an hour or so, and have it cut itself down, and
                            then foxhunt the transmitter.

                            I tried using a pair of mosfets in parallel between the microcontroller
                            and the nichrome we want to use for cut-down, but the mosfets heat up,
                            and the nichrome doesn't.  I'm more of a software guy than a hardware
                            one.  What have people been using for switching their cutdown wires?

                            Thanks for any suggestions!
                            Mike
                            KD2EAT


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                          • Mike Manes
                            It is written, Things should be made as light as possible, but not more so. , with apologies to A. Einstein 73 de Mike W5VSI
                            Message 14 of 21 , Sep 27, 2013
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                              It is written, "Things should be made as light as possible, but not
                              more so.", with apologies to A. Einstein

                              73 de Mike W5VSI

                              On 9/27/13 2:27 PM, wb8elk@... wrote:
                              >
                              >
                              > Relays would be an option for a more traditional ARHAB payload, but as I
                              > understand it they are flying with multiple foil party balloons so every
                              > additional gram of weight is an issue in this case since you can't fill
                              > a foil balloon completely up at launch unless you want a short and low
                              > altitude flight (I tried this a few weeks ago and reached 4300 meters
                              > (14,107 feet). Even a small relay would add significant weight to their
                              > payload in comparison to an SMT FET.
                              > - Bill WB8ELK
                              > -----Original Message-----
                              > From: L. Paul Verhage <nearsys@...>
                              > To: GPSL <GPSL@yahoogroups.com>
                              > Sent: Fri, Sep 27, 2013 12:16 pm
                              > Subject: Re: [GPSL] Seeking advice on nichrome cut-down from microcontroller
                              >
                              > Relays. They need more current to close, but don't have the voltage
                              > drop. The relay is closed for such a short time that its current draw is
                              > insignificant.
                              > Paul
                              > On Sep 26, 2013 8:34 PM, "Michael Hojnowski" <kd2eat@...
                              > <mailto:kd2eat@...>> wrote:
                              >
                              > Hiya,
                              >
                              > I've got a microcontroller and radio set up to send aloft on a balloon.
                              > We hope to let it go for an hour or so, and have it cut itself down, and
                              > then foxhunt the transmitter.
                              >
                              > I tried using a pair of mosfets in parallel between the microcontroller
                              > and the nichrome we want to use for cut-down, but the mosfets heat up,
                              > and the nichrome doesn't. I'm more of a software guy than a hardware
                              > one. What have people been using for switching their cutdown wires?
                              >
                              > Thanks for any suggestions!
                              > Mike
                              > KD2EAT
                              >
                              >
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                              > Yahoo! Groups Links
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                            • wb8elk
                              I have used the logic-level gate RFP12N10L FET (less than a buck from Digikey) for nichrome cutdowns (and other things) quite successfully for years now
                              Message 15 of 21 , Sep 27, 2013
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                                I have used the logic-level gate RFP12N10L FET (less than a buck from Digikey) for nichrome cutdowns (and other things) quite successfully for years now activated by a microcontroller output. It is not in a SMT package however (TO220). The big brother to this one is also available from SparkFun and can be used as well (RFP30N06LE). The important thing to note about it is that when you select a FET that the Gate voltage to turn the device fully on has been fabricated to be activated by logic levels (i.e. 3 to 5 volts) and it has a very low Rds. Make sure that any device you plan to use this way has a logic-level gate...otherwise you will not fully turn the device on as Mike Manes mentioned in his previous post.
                                 
                                The SMT one listed in the posts by Anthony and Dave from the UK should be just fine for your purposes.
                                - Bill WB8ELK
                                 
                                 
                                 
                                 
                                -----Original Message-----
                                From: Michael Hojnowski <kd2eat@...>
                                To: GPSL list <GPSL@yahoogroups.com>
                                Sent: Thu, Sep 26, 2013 9:34 pm
                                Subject: [GPSL] Seeking advice on nichrome cut-down from microcontroller

                                 
                                Hiya,

                                I've got a microcontroller and radio set up to send aloft on a balloon.
                                We hope to let it go for an hour or so, and have it cut itself down, and
                                then foxhunt the transmitter.

                                I tried using a pair of mosfets in parallel between the microcontroller
                                and the nichrome we want to use for cut-down, but the mosfets heat up,
                                and the nichrome doesn't. I'm more of a software guy than a hardware
                                one. What have people been using for switching their cutdown wires?

                                Thanks for any suggestions!
                                Mike
                                KD2EAT
                              • Mike Manes
                                I got the spes for Dave s FET, and it is fine for the pyro initiator that he uses on the LOHAN project, but with +3Vgs, it won t pull the 5A that we see on our
                                Message 16 of 21 , Sep 27, 2013
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                                  I got the spes for Dave's FET, and it is fine for the pyro initiator
                                  that he uses on the LOHAN project, but with +3Vgs, it won't pull the
                                  5A that we see on our burners. It MIGHT be better to use a Darlington
                                  power BJT, which will saturate with less than 3V Vbe, but has a Vce-sat
                                  like 1.5V @ 3A Ic with Ib of 3 mA. E.g., Fairchild KSD560 in a TO-220
                                  package.

                                  BTW, Bill posted a query about a magnetic cutdown device that was
                                  mentioned in one of the Vin Lally papers. I couldn't find any more
                                  details about it either, but speculate that it might operate much
                                  like a maglatch relay, which uses a permanent magnet to hold the
                                  relay closed (or open), with a coil surrounding the PM carrying
                                  current which creates a field that BUCKS that of the PM, thus
                                  allowing the magnet to let go. This would work for a light balloon
                                  payload, which can't supply a continuous electromagnet current
                                  in flight, but can supply a brief, high-current pulse.

                                  My battery-operated programmable furnace thermostat uses maglatches
                                  to close the 24 VAC control circuit.

                                  73 de Mike W5VSI

                                  On 9/27/13 2:43 PM, wb8elk@... wrote:
                                  >
                                  >
                                  > I have used the logic-level gate RFP12N10L FET (less than a buck from
                                  > Digikey) for nichrome cutdowns (and other things) quite successfully for
                                  > years now activated by a microcontroller output. It is not in a SMT
                                  > package however (TO220). The big brother to this one is also available
                                  > from SparkFun and can be used as well (RFP30N06LE). The important thing
                                  > to note about it is that when you select a FET that the Gate voltage to
                                  > turn the device fully on has been fabricated to be activated by logic
                                  > levels (i.e. 3 to 5 volts) and it has a very low Rds. Make sure that any
                                  > device you plan to use this way has a logic-level gate...otherwise you
                                  > will not fully turn the device on as Mike Manes mentioned in his
                                  > previous post.
                                  > The SMT one listed in the posts by Anthony and Dave from the UK should
                                  > be just fine for your purposes.
                                  > - Bill WB8ELK
                                  > -----Original Message-----
                                  > From: Michael Hojnowski <kd2eat@...>
                                  > To: GPSL list <GPSL@yahoogroups.com>
                                  > Sent: Thu, Sep 26, 2013 9:34 pm
                                  > Subject: [GPSL] Seeking advice on nichrome cut-down from microcontroller
                                  >
                                  > Hiya,
                                  >
                                  > I've got a microcontroller and radio set up to send aloft on a balloon.
                                  > We hope to let it go for an hour or so, and have it cut itself down, and
                                  > then foxhunt the transmitter.
                                  >
                                  > I tried using a pair of mosfets in parallel between the microcontroller
                                  > and the nichrome we want to use for cut-down, but the mosfets heat up,
                                  > and the nichrome doesn't. I'm more of a software guy than a hardware
                                  > one. What have people been using for switching their cutdown wires?
                                  >
                                  > Thanks for any suggestions!
                                  > Mike
                                  > KD2EAT
                                  >
                                  >
                                  >
                                • HarryM
                                  Here’s the MosFET I use... http://www.onsemi.com/pub_link/Collateral/NTMD6N02R2-D.PDF A DTMF receiver turns on a 555 timer that triggers both gates. 73 Harry
                                  Message 17 of 21 , Sep 28, 2013
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                                    Here’s the MosFET I use...
                                     
                                     
                                    A DTMF receiver turns on a 555 timer that triggers both gates.
                                     
                                    73 Harry
                                    KC5TRB
                                  • Mike Manes
                                    Yep. That s a good one, Harry. 73 de Mike W5VSI
                                    Message 18 of 21 , Sep 28, 2013
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                                      Yep. That's a good one, Harry.
                                      73 de Mike W5VSI

                                      On 9/28/13 11:23 AM, HarryM wrote:
                                      >
                                      >
                                      > Here’s the MosFET I use...
                                      > http://www.onsemi.com/pub_link/Collateral/NTMD6N02R2-D.PDF
                                      > A DTMF receiver turns on a 555 timer that triggers both gates.
                                      > 73 Harry
                                      > KC5TRB
                                      >
                                      >
                                      >
                                    • HarryM
                                      It was recommended to me by Michael Gray, KD7LMO. God rest his soul! 73 Harry Yep. That s a good one, Harry. 73 de Mike W5VSI
                                      Message 19 of 21 , Sep 28, 2013
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                                        It was recommended to me by Michael Gray, KD7LMO.
                                        God rest his soul!
                                        73 Harry
                                         
                                         

                                        Yep. That's a good one, Harry.
                                        73 de Mike W5VSI

                                      • Michael Hojnowski
                                        Gang, As the Cornell Amateur Radio Club is getting into balloons, we re (ok, ok, I am!) intrigued by long-flight (multi-day) pico balloons. Being in the US,
                                        Message 20 of 21 , Oct 3, 2013
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                                          Gang,

                                          As the Cornell Amateur Radio Club is getting into balloons, we're (ok,
                                          ok, I am!) intrigued by long-flight (multi-day) pico balloons. Being in
                                          the US, APRS seems like the right technology to use for telemetry, but
                                          we're struggling a bit to work out a low wattage transmitter. The lower
                                          the wattage, the longer we figure we can track. It doesn't seem like
                                          reaching an APRS rf gateway will be difficult, even at low wattages,
                                          from a great height.

                                          We're not afraid to build something, if need be. Does anyone have
                                          suggestions? Crystals in the right range seem to be as rare and
                                          expensive as hens teeth. I feel like we're missing something.

                                          Mike / KD2EAT
                                        • Anthony Stirk
                                          Evening Mike, Try decase the Radiometrix HX1 it comes in about 2g and power it using a step up. You re still going to be pushing it for a pico. Alternately try
                                          Message 21 of 21 , Oct 3, 2013
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                                            Evening Mike,

                                            Try decase the Radiometrix HX1 it comes in about 2g and power it using a step up. You're still going to be pushing it for a pico. Alternately try a custom radio design based on the SI446x chips  which are the same ones we are using on our picos over the pond. I believe these can be run down to the 2 meter band but I've not tried doing APRS on one. 

                                            Cheers,

                                            Anthony M0UPU


                                            On Thu, Oct 3, 2013 at 8:11 PM, Michael Hojnowski <kd2eat@...> wrote:
                                             

                                            Gang,

                                            As the Cornell Amateur Radio Club is getting into balloons, we're (ok,
                                            ok, I am!) intrigued by long-flight (multi-day) pico balloons. Being in
                                            the US, APRS seems like the right technology to use for telemetry, but
                                            we're struggling a bit to work out a low wattage transmitter. The lower
                                            the wattage, the longer we figure we can track. It doesn't seem like
                                            reaching an APRS rf gateway will be difficult, even at low wattages,
                                            from a great height.

                                            We're not afraid to build something, if need be. Does anyone have
                                            suggestions? Crystals in the right range seem to be as rare and
                                            expensive as hens teeth. I feel like we're missing something.

                                            Mike / KD2EAT


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