ir on-off switch

Discussion in 'The Projects Forum' started by shoban, Aug 27, 2012.

  1. shoban

    Thread Starter New Member

    Jul 27, 2012
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    hi ,
    i picked up and assembled this circuit from
    http://www.extremecircuits.net/2010/05/on-off-infrared-remote-control.html

    on powering up, the triac just switches itself on and off without any input from the remote.
    don't know whats going wrong....have used TSOP1838 as the ir receiver, rest all seems ok.

    btw i'm a mechanical engg....so my skills in electronic are limited:).

    any help is welcome:).

    [​IMG]
     
  2. wayneh

    Expert

    Sep 9, 2010
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    I'd try disconnecting R5 to see which side of the circuit might be misbehaving. If the toggling continues, you know it's not the whole left hand side of the circuit. If the toggling is slow enough, get in there and probe the key voltages.

    [update] You could also disconnect the wire from the connection to IC2B pin 9 and manually take it to ground to see if the right hand side is working.
     
    Last edited: Aug 27, 2012
  3. DickCappels

    Moderator

    Aug 21, 2008
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    That doesn't look like a very sophisticated decoder, therefore, it might not be looking for a complex coded signal.

    Is it possible that you are using a light bulb for the load, and that the IR sensor is seeing the IR from the bulb?

    By the way, thank you for the foresight of posting the schematic :)
     
  4. shoban

    Thread Starter New Member

    Jul 27, 2012
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    hi...tried disconnecting R5 and the triac remained in off condition not toggling.
    disconnected ic2b pin 9 and grounding pin 2 of the opto results in switching on of the triac as long as it is kept grounded.
    is it supposed to remain on once the pin2 opto ground is removed?

    i am using a lamp as the load but i have kept it isolated from the ir sensor..

    toggling is happening once every 3-4 secs...
     
  5. wayneh

    Expert

    Sep 9, 2010
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    OK, so the problem is on the LHS (left hand side) of the schematic. I think your tests showed that opto LED on = light on, opto LED off, light off. Right?

    My hunch is that the IR receiver only produces a pulse - not a continuous output - when modulated IR is detected. Many IR receiver modules work this way. You're seeing those pulses go by followed by a reset. Look up the specs of the exact detector you are using. It's a a "module" and not just a simple photodiode or phototransistor, right?
     
  6. shoban

    Thread Starter New Member

    Jul 27, 2012
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    hi...
    on disconnecting R1 and output terminal of ir sensor the triac remains off.
    then if i touch R1 with my finger momentarily i am able to switch on/off the triac.
    If i keep my finger continuously on R1 then the triac goes into fast on-off toggle.

    just some layman trouble shooting...:) i cant think of anything clever :)

    help...
     
  7. shoban

    Thread Starter New Member

    Jul 27, 2012
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  8. shoban

    Thread Starter New Member

    Jul 27, 2012
    15
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  9. wayneh

    Expert

    Sep 9, 2010
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    OK, well the zener is a crude voltage regulator, holding the voltage at the receiver at a constant 5.1V. R1 is there to protect the zener from over-current.

    How about trying this: Disconnect R2 at either end and watch the voltage there. I think you'll see the same toggling effect. If not, it's not the receiver as I suspect.

    Oh, you're seeing the toggling even without a remote pointed at the receiver? That might indicate a noise problem. What's your power source? Are working under florescent lights?
     
  10. shoban

    Thread Starter New Member

    Jul 27, 2012
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    ..its all up in smoke..:(....will make a new one and get back at it
     
  11. wayneh

    Expert

    Sep 9, 2010
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    Whoa! What happened?
     
  12. shoban

    Thread Starter New Member

    Jul 27, 2012
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  13. shoban

    Thread Starter New Member

    Jul 27, 2012
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    oh....it got shorted out on some metal wire one the table....main operated circuits are such a pain. :)

    if its noise thats the problem what should i do.......do i raise the R1 to say 10 Mohm and put a cap across output of sensor and ground in the first circuit.
     
  14. shoban

    Thread Starter New Member

    Jul 27, 2012
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    i'm using 230v main to power up the circuit......the circuit was toggling on its own even when the sensor was covered......it stopped when i disconnected the output of the sensor.

    will make a new one in 2-3 days...:)
     
  15. wayneh

    Expert

    Sep 9, 2010
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    Ooh, a pain and generally a forbidden topic here, for safety reasons. Not sure where this one falls.
     
  16. shoban

    Thread Starter New Member

    Jul 27, 2012
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    agreed its not safe to work with mains but i guess it has its own merits....going to use an isolation transformer this time on.
    any idea whats the value for C4 in post #12 .may be i will try and make the one in post #12.......seems better with a regulated power supply...
     
  17. shoban

    Thread Starter New Member

    Jul 27, 2012
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    guidance is much appreciated.
     
  18. absf

    Senior Member

    Dec 29, 2010
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    I would put a 10uF parallel with 100nF there. But the writing looked like 20nF.

    Allen
     
  19. wayneh

    Expert

    Sep 9, 2010
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    Look up the datasheet for that regulator and use the capacitor size recommended there. Nano or pico, either seems too small.
     
  20. shoban

    Thread Starter New Member

    Jul 27, 2012
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    datasheet shows in general application to use .33uF in input side and 100 nF in outputside..... just wondering if the circuit is using these small values for any particular reason?
     
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