Problem with Infrared Remote Control circuit

Discussion in 'General Electronics Chat' started by hazim, Aug 27, 2010.

  1. hazim

    Thread Starter Active Member

    Jan 3, 2008
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    Hi all
    I'm building the circuit in this web page: http://www.aaroncake.net/circuits/irremote.asp . I used SS8550 instead of 2N2907 (Q2), every thing else is the same. The circuit didn't worked... I tried 2N3906 and the circuit didn't worked too. I think C5 should be 10nF as C1 and not 100n (for frequency congruence?) but both values didn't worked.
    Any help is appreciated.
    Hazim
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    First thing is to figure out if it's the transmitter or receiver that isn't working. Substitute a visible red LED in for the IR one to see if it's lighting up at all.

    While a scope would be most helpful in this situation it can probably bne worked through with a simple voltmeter. For now, keep the cap values as stated in the parts list.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The transmitter circuit is no good.

    Try building a transmitter using a 555 timer.

    Actually, try increasing the battery voltage to around 5-6v - then you should see some output from it.

    Add a resistor in series with the LED so that you don't burn it up.
     
    Last edited: Aug 27, 2010
  4. hazim

    Thread Starter Active Member

    Jan 3, 2008
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    I use a digital camera to see the transmitter IR LED light, I also have built a remote control tester circuit... on the camera's screen I see the LED lighting up all the time I'm pressing the switch, while in any other remote control the LED lights up intermittently with period about 0.5s (this is the length of the code I think), but in the circuit I'm building the LED lights continuously (with frequency determined by C1, R1 and R2). So I don't know if this is the problem.

    SgtWookie, I'll try to use 555 timer for the transmitter tomorrow, but actually I prefer a small two transistor transmitter with 3V supply. the 555 needs 4.5V min while most appliances remote control uses 3V batteries. I'll use lithium coin cell, if I used a 555 timer then maybe I'll use two thin 3V cells. I'm very concerned about the volume of the transmitter.

    Regards,
    Hazim
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    Did you add the resistor that is missing as mentioned in note#4 of the article?
     
  6. wannaBinventor

    Member

    Apr 8, 2010
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    I beleive there are some low voltage 555s out there. You can make a relaxation oscillator out of some NAND gates if you have some of those laying around that will work on the voltages you'd like.

    See this thread for some help on getting the IR transmitter to work with two 555s. I posted it last month looking for some help and originally proposed a bad schematic that didn't work. If you read all the replies, you will see the modifications I made to get it to work.

    http://forum.allaboutcircuits.com/showthread.php?t=40386
     
    hazim likes this.
  7. hazim

    Thread Starter Active Member

    Jan 3, 2008
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    Thanks, I'll check the thread right now. I don't want to use an IC with more than 8 pins so I may use 555 timer not CMOS NAND ICs...

    Audioguru, I may try it tomorrow but I don't think this will solve the problem. The transmitter supply voltage is only 3V, the led is working on high frequency so its not a big problem? especially because that the series resistor won't affect the frequency but prevent the LED from burning up.
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    An ordinary 555 has a minimum supply of 4.5V. A Cmos 555 has a minimum supply of 1.5V to 2.0V but its output current is very low and needs a booster transistor on its output to drive an LED.

    The transmitter is a very simple "Mickey Mouse" circuit. Its frequency is probably wrong and changes all over the place.
    The receiver uses a 42 years old 741 opamp that has poor performance above only 9kHz (modern opamps cost the same but work well up to 100kHz). The 741 opamp has its input floating without a DC voltage reference without the important missing resistor to ground.
     
  9. hazim

    Thread Starter Active Member

    Jan 3, 2008
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    I can't get a CMOS 555 timer now, this is not a problem, I may use 2x3V cells.
    No they are using LM308 opamp, not a big difference right? my main problem is that I'm far from any electronic components store.
     
    Last edited: Aug 28, 2010
  10. Audioguru

    New Member

    Dec 20, 2007
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    The LM308 is older and slower than the 42 years old 741 opamp. It is obsolete and has not been made for 12 years.
    I would use a TL071 or TL081 opamp (minimum supply is 7V) that is available nearly everywhere. Their frequency compensation capacitor is built-in and the pins numbers are the same as the LM308.
     
  11. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I think what a lot of us are saying is that in this instance it might be easier and better to stat off with a new design. I built a similar circuit using a modern IR receiver http://www.vishay.com/docs/82090/tsop48xx.pdf but it exects to see more than just the presence of a signal at a set frequency.

    A 555 will drive an LED directly and could be set up for something like 10 KHz, then you'd just need a phototransistor driving an op amp designed to be a bandpass filter/amplifier as the receiver.

    I had distance to consider with mine so I used an IR emitter pulsed in a high current / low duty cycle mode. 100' was easy, probably go much further but I'm physically limited due to the area it's used in. If you really need some distance and the transmitter/receiver are to be in set locations you can add some simple optics and extend the range of these circuits by quite a bit.

    A second on the TL08x series op amps, they're somewhat dated but inexpensive, easy to find and easy to work with.
     
  12. hazim

    Thread Starter Active Member

    Jan 3, 2008
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    Ok thanks, later I'll buy some TL071 opamps. I want to use the transmitter from about 4 to 5 meters only far from the receiver... But anyway I think I can build an easy IR remote control circuit even using old parts. can't I do it with frequency around 10kHz with LM308?
     
  13. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I don't see why not.
     
  14. Audioguru

    New Member

    Dec 20, 2007
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    The datasheet for the obsolete LM308 shows that is max full output frequency is 12kHz when its frequency compensation capacitor is only 3pF and is 1.2kHz when the capacitor is 30pF. This project uses a capacitor that is 100pF so the max full output frequency is about only 400Hz.
    Modern opamps like the TL071 or TL081 go up to 100kHz easily and have the frequency compensation capacitor built-in.
     
  15. marshallf3

    Well-Known Member

    Jul 26, 2010
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    That IC is THAT bad?

    He's going to have to run to Radio Shack and buy a TL082 then just use half of it.
     
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