From: David N. <jud...@ad...> - 2002-05-10 17:00:39
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I am disabled and a friend is building an IR transmitter for me to use = with LIRC and WinLIRC. The circuit we chose is the "improved" transmitter by Enrique Vidal: http://www.lirc.org/improved_transmitter.html He is having trouble getting it to work on his NT box and we haven't = tried it yet on my Linux machine. He is concerned that he has built the = circuit incorrectly. Would you please look at his comments below and provide any advice you = may have. David > I'm getting a positive connection, a charged capacitor, and a > measurable (DTR-GND) voltage drop during the sending of codes on = WinNT. > > The problem is the LED in the circuit isn't getting enough juice to = light up > (this also affects IR output, which is too weak to work). My gut still > suspects the PNP and NPN transistors aren't properly rated, or perhaps = I > have them hooked up wrong... To be honest, I just went to Radio Shack = and > looked for a matching NPN and PNP and of the poor smattering of = offerings, > selected the lowest voltage rated ones I could find there (40 volt). = This > may be too high as the circuit seems to be getting 8-10 volts from my > measurements across DTR and GND. > > Another possibility is that I don't understand transistor schematic > diagrams... in building the circuit this far, I've assumed the little arrow > facing inwards is the "collector" of the PNP and the little arrow = facing > outwards is the "emitter" of the NPN. This may not be true as it's = just a > logical "guess" on my part. I'm quite sure I've got the cathodes and anodes > correct on all the diodes... I'm also quite confident I've got all the > resistors exactly as prescribed. The only other question lingering is = if > there are different kinds of LEDs (different power ratings)... I've assumed > they're pretty much all the same. > > Perhaps you could write to the community or author of the circuit and = see if > anyone can suggest digi-key part numbers for the transistors so we can = at > least rule that out. The only other question is that I ended up = getting a > 4700 uf capacitor rather than a 4000 uf one since that was all RS had. = My > thinking was that a little bigger would be OK, it would just hold a slightly > bigger charge... again I'm guessing as to if this could affect = success. |
From: Craig B. <cra...@bt...> - 2002-05-10 17:30:17
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From what I remember the arrow is always the emitter, the direction of = the arrow determines NPN or PNP. Hope this helps Craig ----- Original Message -----=20 From: David Norwood=20 To: lir...@li...=20 Sent: Friday, May 10, 2002 5:59 PM Subject: Trouble with the "improved" IR transmitter circuit=20 I am disabled and a friend is building an IR transmitter for me to use = with LIRC and WinLIRC. The circuit we chose is the "improved" transmitter = by Enrique Vidal: http://www.lirc.org/improved_transmitter.html He is having trouble getting it to work on his NT box and we haven't = tried it yet on my Linux machine. He is concerned that he has built the = circuit incorrectly. Would you please look at his comments below and provide any advice you = may have. David > I'm getting a positive connection, a charged capacitor, and a > measurable (DTR-GND) voltage drop during the sending of codes on = WinNT. > > The problem is the LED in the circuit isn't getting enough juice to = light up > (this also affects IR output, which is too weak to work). My gut = still > suspects the PNP and NPN transistors aren't properly rated, or = perhaps I > have them hooked up wrong... To be honest, I just went to Radio = Shack and > looked for a matching NPN and PNP and of the poor smattering of = offerings, > selected the lowest voltage rated ones I could find there (40 volt). = This > may be too high as the circuit seems to be getting 8-10 volts from = my > measurements across DTR and GND. > > Another possibility is that I don't understand transistor schematic > diagrams... in building the circuit this far, I've assumed the = little arrow > facing inwards is the "collector" of the PNP and the little arrow = facing > outwards is the "emitter" of the NPN. This may not be true as it's = just a > logical "guess" on my part. I'm quite sure I've got the cathodes and anodes > correct on all the diodes... I'm also quite confident I've got all = the > resistors exactly as prescribed. The only other question lingering = is if > there are different kinds of LEDs (different power ratings)... I've assumed > they're pretty much all the same. > > Perhaps you could write to the community or author of the circuit = and see if > anyone can suggest digi-key part numbers for the transistors so we = can at > least rule that out. The only other question is that I ended up = getting a > 4700 uf capacitor rather than a 4000 uf one since that was all RS = had. My > thinking was that a little bigger would be OK, it would just hold a slightly > bigger charge... again I'm guessing as to if this could affect = success. |
From: Enrique V. <ev...@it...> - 2002-05-10 18:21:40
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Regarding David's question, 2002-05-10: Craig Barnes dixit: > >From what I remember the arrow is always the emitter, the > >direction of the arrow determines NPN or PNP. > > ----- Original Message ----- > From: David Norwood > I am disabled and a friend is building an IR transmitter for > me to use with LIRC and WinLIRC. The circuit we chose is the > "improved" transmitter by Enrique Vidal: > http://www.lirc.org/improved_transmitter.html > [...] > He is having trouble getting it to work on his NT box and we > haven't tried it yet on my Linux machine. He is concerned > that he has built the circuit incorrectly. > [...] > > Another possibility is that I don't understand transistor > > schematic diagrams... in building the circuit this far, I've > > assumed the little arrow facing inwards is the "collector" of > > the PNP [...] Actually, Craig's diagnostic is the correct one. Wiring the PNP transistor in the wrong way will never work! Best, Enrique. |
From: Stephen D. <st...@da...> - 2002-05-11 07:45:59
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On Fri, 10 May 2002, David Norwood wrote: > > Another possibility is that I don't understand transistor schematic > > diagrams... in building the circuit this far, I've assumed the little > arrow > > facing inwards is the "collector" of the PNP and the little arrow facing > > outwards is the "emitter" of the NPN. This may not be true as it's just a > > logical "guess" on my part. The little arrow always denotes the emitter, whether it points in OR out. HTH, Steve |