IR Sensor Troubleshooting

Discussion in 'General Electronics Chat' started by uriahsky, Feb 11, 2013.

  1. uriahsky

    Thread Starter Active Member

    Apr 27, 2009
    42
    2
    I have been having a real hard time with this particular pcb and am stuck.

    This is a sensor for a little game called Mini Dunx by ICE GAME. It is a redemption game where little kids throw small basketballs through a hoop and score points. There is an IR Transmitter on one end of the basket and a two receivers on the other end. Very simple but I can't figure out what is wrong.

    The IR sensors are working. They go to a op amp and from there to the Inverters shown in the schematic. I didn't include the Op Amp schematic because it seems to be working like it should. With the transmitter not shining into the receiver I get 5Volts at the input into the inverter. When I shin the transmitter into the receiver the 5volt drops to 0 volts at the input into the first pair of inverters but at the output nothing happens.

    That is the problem, why don't I get a voltage change at the output of the first pair of inverters? And why doesn't the LED turn on and off?

    The IR pcb is linked to the main board by that sense line and once it reaches the main board it goes through those 10K resistor network and into a 74hc165. Which seems to be OK.

    When I disconnect the sense line I get 5 volts on the main pcb at that 10K resistor network. When that goes to zero the games scores a point. But when I hook that sense line back up to the IR pcb the 5 volts drops to 0 volts and stays there regardless of the transmitter being on or off.

    I also checked all of those parts on the schematic out of circuit and they all check OK? Unless I missed something. I replaced the hex inverter a 74LS05 and it made no difference.

    Any ideas on what is going on?
    Can someone explain how this should work.
    Thanks very much,
    Russ
     
  2. timescope

    Member

    Dec 14, 2011
    298
    44
    Hi,
    The 74LS05 is an open collector device and the output requires a pullup resistor.

    There might be a short circuit to ground at the output of the inverters.

    Both NOT1 and NOT2 inputs should be L (0v) for the output to be H (5v). This means that the IR transmitter should be aligned to activate both sensors.

    Timescope
     
  3. uriahsky

    Thread Starter Active Member

    Apr 27, 2009
    42
    2
    Thanks for pointing out that I needed both IR receivers active at the same time to get this to work.

    I tried it with two independent transmitters pointing at each receiver and it does work like it should.

    I think maybe the original transmitter is getting weak if that is possible? Because when I point the original transmitter at it, it isn't strong enough to trigger both receivers. I am going to swap in another transmitter to see if that helps.

    That was sure frustrating. I hope I learned something from this.
    Thanks again,
    Russ
     
  4. electron_prince

    Member

    Sep 19, 2012
    93
    3
    I am sorry. I am feeling too lazy cause i just returned from the college. I'd read your post later and edit my post. In the mean while I want to ask you something. why are you making things so complicated? i mean that an IR sensor can be prepared from two IR led (one forward biased and one reversed). and one comparator and one preset. and few resistors.
     
  5. timescope

    Member

    Dec 14, 2011
    298
    44
    Hi uriahsky,

    Yes, it is possible that the transmitter is defective. I hope you can get it working properly and make the kids happy.

    Timescope
     
  6. sheldons

    Active Member

    Oct 26, 2011
    616
    101
    you may need to replace the ir emitter in the handset,have a look at the intensity of the light coming from the handset when a button is pressed (you need to view it via your phone camera etc) or replace the ir sensor on the reciever
     
  7. uriahsky

    Thread Starter Active Member

    Apr 27, 2009
    42
    2
    I have been working on this thing for a few days and I am still not having much luck.

    I must have ten or more different pairs of IR LEDs around here from past repairs and parts off other boards but few of them match up and most all of them don't give me enough distance.

    Is there a way to increase power to a IR transmitter?

    Or to increase the strength of the receiver?

    I tried adding a 100 ohm pot to where the 100 ohm series resistor was on the transmitter but it didn't make much of a difference as I adjusted it.

    I also added an extra IR transmitter to the pcb but it still doesn't seem to have the range that is should have.

    I can get a number of them to work but I only get about a six inch range and if I barely tilt the pcb it doesn't connect.

    I noticed some of the new receivers would not even work. Most of these components I have don't have part numbers so I can't do much research.

    Is there a way to find IR pairs that travel over a distance of a about 1.5 feet. Is there a spec I should be looking for?

    They want about 100.00 for a replacement pcb but I can't do that knowing it is probably a four dollar part, and of course I want to learn more about the circuit.

    Thanks again,
    Russ
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    Make sure you have 5V from the V2 supply. Based on the measurements shown I think either that is gone or the cap is shorted.
    And make sure R5 is not open.

    I re-read your
    post's, now not sure.

    Are you still having the same symptoms on the posted diagram?
     
    Last edited: Feb 16, 2013
  9. timescope

    Member

    Dec 14, 2011
    298
    44
    Something must be wrong because IR usually works across a room with a remote control powered by 3v batteries. If possible, post a complete schematic as the problems may be caused by a marginal design.

    Timescope
     
  10. uriahsky

    Thread Starter Active Member

    Apr 27, 2009
    42
    2
    I did some experiments I wired up the LED to my power supply and ran up the current from 20mA up to over 500mA and it only changed the range by a few inches. I moved up the voltage to almost over 2 volts and it also only made a difference of a few inches. I still can't go over six inches.

    I found some 1 watt and 3 watt high power IR LEDs on eBay and ordered those up. I will see if that helps.

    It seems most ways to increase the distance involves pulsing the LED so that you can go over the current requirements without damaging the component. I would rather not have to design a new circuit if at all possible. It worked at one time, so it has to be in the parts. I checked all of those parts mentioned and it isn't any of them. It is either that I have the wrong IR LED or the receiver is bad or I missed the obvious, again.
    Thanks
    Russ
     
  11. uriahsky

    Thread Starter Active Member

    Apr 27, 2009
    42
    2
    I finally resolved this. It was the emitter that was burned out, or at least a lot weaker. After going through all of the standard ones found on eBay I managed to find one that was stronger than the others. A SIR311STA that had a range of over a foot. I added an extra one and so far it is working. I hope it lasts. Thanks for all of the help.
    Russ
     
  12. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,826
    All LEDs, including IREmitters have an angle of dispersion. Some emit to near 180 degree (hemisphere) and result in very low intensity at any given point. IR emitters are also available in very focused packages that allow as little as 8 degrees of dispersion. They allow very good intensity at a range.

    IR phototransistor a have a similar set of angles available. Also note that not all IR emitter receiver pairs work together. Some have peak sensitivity anywhere from high 700 nanometer wavelength and have max sensitivity over 1100 nm. Mis-matches can be severe with some phototransistors have a sharp band stop only 50 to 100 mn above there peak sensitivity so watch that factor too.
     
Loading...