IR Detector Circuit "Solved"

Discussion in 'General Electronics Chat' started by killivolt, Dec 7, 2017.

  1. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    Hi, anyone who might have an answer to this question. In another Thread we proposed a circuit operation that will require this IR Detector.

    I'm not sure what I'm doing wrong, I'm doing this with SMPS 12vdc and based on this circuit.

    [​IMG]
    How can I test the LTR4206E to see if I have burnt it out.

    kv
     
  2. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    Disconnect it from the '555 and connect that end of it to 0V, then measure the voltage across it. If you get a couple of volts it's probably OK.
     
  3. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    Thank you, thats what I thought, when I'm testing it do I need resistance or does it check much like an Photo Diode? I may have burnt it out testing it or just wired my circuit wrong or something. I've never been able to make this part work.:oops:

    kv :)
     
  4. AlbertHall

    AAC Fanatic!

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    Leave the other end connected to the resistor to limit the current.
     
  5. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    Check, resistor stays in :D

    Thanks again, learn something everyday on this site. :)

    kv
     
    Last edited: Dec 7, 2017
  6. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    @AlbertHall, yes, both I purchased are bad. Either I did something wrong which is usually the case or they came this way? Which I doubt.

    kv
     
  7. AlbertHall

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    Are you sure you have the polarity correct?
    upload_2017-12-8_15-31-15.png
     
  8. BobTPH

    Senior Member

    Jun 5, 2013
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    That phototransistor has an absolute maximum voltage of 5V and you are supplying 12V. It is likely damaged now.

    Bob
     
  9. DickCappels

    Moderator

    Aug 21, 2008
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    If you are concerned about your IRLED run about 20 ma through it (the forward drop will be near 1 volt) and look at it with a camera -if your camera doesn't have a great IR stop filter you will be able to see the LED glow in the picture. You might have to try more than one camera.

    If you are concerned about your photodetector, connect as shown in your schematic and monitor the voltage across the resistor with a digital voltmeter and then point it at a nearby incandescent lamp and see if that makes the voltage across the resistor increase.
     
  10. DickCappels

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    Aug 21, 2008
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    The 5V specification tells the maximum reverse voltage, probably related to the reverse breakdown voltage of the base-emitter junction. Even the detector were installed backwards, it is likely that the resistor would limit the current and that might save the detector in that case.
     
  11. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    Ya, I'm sure about the connection. But, if I was checking it with my DMM no resistor I probably blew it up. I tried both of them in circuit last year when I was trying to get this part of the circuit operational. There is no doubt, both are open in both directions.

    I can see a voltage drop on the IRLED, I got rid of my phone that didn't have a good IR filter. My new does. I went home and grabbed a remote and shot it, still nothing.


    Yup, first thing I did and nothing no change in Voltage. I'm sure I defunct it or it shipped this way, no biggie their cheap.

    kv

    Edit: I should have ordered more but thought it would be my IRLED that I would burn up, purchased 9 of them. :p Only purchased 2 of the detectors :oops:
     
  12. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    I'll order new ones and check them according to spec with a resistor before I install them.

    Thank you to everyone that contributed, your all great. Happy Hollidays.

    I'll make sure I bring this through after I get my new ones, checking them before installation and report.

    kv
     
  13. be80be

    AAC Fanatic!

    Jul 5, 2008
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    You do no that in a lite room you may not see a change
    This light turns on most so the output wouldn't change it would stay at ground
    IMG_20171208_205947.jpg
     
    Last edited: Dec 8, 2017
  14. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    I thought about that when I seen this post here https://www.evilmadscientist.com/2007/a-simple-and-cheap-dark-detecting-led-circuit/ I became confused.

    With the light off in the room and I measured still nothing V out, the same circuit here different site http://cr4.globalspec.com/thread/75590/Light-Sensing-Circuit had little success.

    Which now you can see my frustration, which is it light sensing or Dark sensing. Both remain at ground no Voltage drop.

    kv
     
  15. DickCappels

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    Aug 21, 2008
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    It is not clear to me whether you are troubleshooting the phototransistor or the LED. If the LED gives you about a 1 volt drop, then for now assume it is ok.

    Below is the base diagram of the phototransistor. The diagram that RobertHall posted is for the LED>
    upload_2017-12-9_22-56-20.png
    If you ground the emitter of the phototransistor and connect a suitable resistor (say 22k or so) from the collector to the positive power supply and monitor the voltage drop across the phototransistor,the voltage drop will change when you switch between blocking light entering the transistor and shining an incandescent light into it. Florescent lamps might not have enough IR to do the job.

    A. Are you troubleshooting the detector?
    B. If so, does the voltage across the collector resistor change?
    C. What is the value of the collector resistor?
    D. What voltage(s) do you see across the resistor? (from your previous post I would expect the full power supply voltage to be across the resistor all the time.
     
  16. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    Yes, zero, it's the LTR that seems non responsive. I attached a resistor to positive 12 vdc and put the cathode to ground 0 vdc the on state should have a voltage drop it acts as if it's an open either lights on or off exposed to IR or not. Same if I measure forward voltage with the Diode check on my meter out of circuit connected to a resistor. Lights on or off same result.

    The circuit I intend to use this on, is in my "Smoker Circuit Design" Thread, now that I understand a little more I realize that with smoke in the stack it would send power to a comparator to read the change of state or vice versa when that power changes state again with no smoke which would signal time for an auger filled with wood to feed a smoke box.

    kv
     
    Last edited: Dec 9, 2017
  17. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    Yes, we can assume the LED is working. It's the detector I'm talking about that had me confused. But, I think I understand how it could work in a circuit to trigger a response for my auger. BTW, I made a mistake while saying I removed it from the 555 it's the detector, sorry about that :oops:

    kv

    Edit: I've edited the above post with 555 confusion about LTE2718C or LTR4206E so it makes more sense.
     
    Last edited: Dec 9, 2017
  18. be80be

    AAC Fanatic!

    Jul 5, 2008
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    I didn't have a IR to show you but the same thing happens say the switch is the light you close it the pictures show what happens
    you open there no light you can see what happens too
    IR Light on
    turnedON.png
    IR light off
    off.png
     
  19. killivolt

    Thread Starter Distinguished Member

    Jan 10, 2010
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    Update:
    As to the related diagrams both how you show yours and how I missed Cathode Emitter on the LED and detector diagrams posted by @DickCappels and @AlbertHall ( In a PM DickCappel was able to see my mistake and point out as most people who encounter LED's over the years always consider the Flat or short stem always the Collector not the Emitter. The LTR4206E has the configuration short stem or flat side is the Emitter, this mis-representation could well have damaged the parts.

    Now that I have it connected correctly in circuit, I did see a voltage increase on the neutral side but, still not amazing went from 0vdc to 0.027vdc when I connect the IRLED when the IRLED is out of circuit it returns to 0vdc.

    But, remember this thing has been hooked to a circuit improperly as well as being checked with my DMM and no resistor. While the Voltage from my DMM is only 2.67vdc when I diode mode when check it in this mode resistor or no resistor the LTR4206E Detector appears open in either direction of polarity.

    I'll order some new LTR4206E from Mouser this afternoon and do a double Update.

    Oh, good to talk with you be8obe. Been awhile.

    Thanks for all the contributions, I learn something on this big time, just when I think I know I''m reminded how much there is to learn.

    Regards,

    kv
     
  20. AlbertHall

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    Jun 4, 2014
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    What value resistor do you have connected between the collector of the LTR and the supply?
     
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