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We have a mouse (or something) getting into cabinets. My wife doesn't want to kill it, and the no-kill mousetrap isn't catching it. So, I am modifying a trap with an IR emitter / detector so I know when the little fella is there. I naively bought an infrared emitter (RS 276-0143) and biased it up, and then a 276-640 receiver (with no data sheet). Using two "D" cells to create 3v rail. I'm assuming the emitter is working. The receiver "output" rails up to 3V when GND and Vcc are connected. A 5K resistor on the output to GND pulls it low. When I turn on the emitter 2 inches away, nothing happens. I'm already down to .6 mA on the output with the 5K. Any ideas? Bigger resistor on the output? Wrong emitter (frequency range), maybe this thing doesn't work for continuous duty?

All in put welcome, I think the mouse is getting bigger.

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    \$\begingroup\$ Please share a schematic, it is a bit easier for me to understand the set-up with a picture than with a word-picture. In case you do not have sufficient reputation, please upload a schematic, even a hand-drawn sketch, to some public image sharing site, and add the link as a comment here - someone will edit the image into your question for you. \$\endgroup\$ Commented Jun 23, 2013 at 15:06
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    \$\begingroup\$ IR emitters usually show up on cameras like in a 'phone or web-cam. That is one handy way to test the emitter. \$\endgroup\$ Commented Jun 23, 2013 at 15:38
  • \$\begingroup\$ As for catching/detecting mice: I set up a web cam with motion detection at a mouse crawl space. With lights! The mice did not seem to mind the light, but were pretty canny about certain traps, jumping right over them. \$\endgroup\$ Commented Jun 23, 2013 at 16:45

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The RS 276-640 is a 38kHz IR receiver module whereas the RS 276-0143 is a high power IR LED. The receiver is expecting a 38kHz pulsed signal not a continuous one. You could try pulsing the IR LED at 38kHz with a simple oscillator.

enter image description here

or use an IR photo transistor

enter image description here

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  • \$\begingroup\$ OK .. thanks, Jim ... that makes perfect sense. Before I build an oscillator (thanks for the schematic), Ida thought there'd be a IR detector that simply conducts (or does something) when it detects continuous IR energy. Maybe I throw the receiver away and find a simple IR detector? Thoughts? \$\endgroup\$
    – davef
    Commented Jun 23, 2013 at 21:03
  • \$\begingroup\$ Yes - a simple IR photo transistor should do the trick Take a look at sunrom.com/sensors/light-infrared/phototransistor virtually any IR photo transistor should do. \$\endgroup\$ Commented Jun 24, 2013 at 8:18
  • \$\begingroup\$ PERFECT! Thanks. We have FOUR mechanical mouse traps on the counter. All four are tripped .. no mice. Gotta this thing built, as right now, we're just feeding them. \$\endgroup\$
    – davef
    Commented Jun 24, 2013 at 11:47
  • \$\begingroup\$ @davef lol - if you want to catch a mouse tie a small piece of chocolate onto the trap trigger with thread then set the trap with a spoon handle so its just about to trip (saves the fingers). Worked every time for me. \$\endgroup\$ Commented Jun 24, 2013 at 13:31
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IR receiver modules like the one cited are designed so that when they are receiving a modulated signal from an infrared remote control they will relay that signal accurately, and when they are not receiving such a signal they will output noise (similar to the way radios and televisions used to output static when they are not tuned to a station). Essentially, any time the signal is higher than the average for the last ~10ms or so it will say there is signal present, and any time it's lower, it will say there's no signal. This means that the strength of signal that's required for reliable detection will depend upon the ambient level of modulated IR, rather than any fixed threshold in the sensor itself. If there's no stray modulated IR, the detector can be very sensitive. Good for a remote-control receiver. Not so good for your application.

While it's possible to use a "steady on" infra red transmitter and receiver, such an approach will require calibration, and ensuring that things stay in calibration may be difficult. Using a microcontroller may allow you to achieve better results. Have the microcontroller turn the IR emitter on and off either randomly or in some pattern, and some time after switching it each time, measure the signal from the receiver. Keep track of the average signal values received when the emitter is on, and when it is off. The difference between the "on" and "off" values should be very significant when the beam is not blocked, and fall off enormously when it is blocked. Since you would be measuring the amount by which the IR pickup changes when the light is switched, rather than measuring an absolute level, the system would be in a sense self-calibrating. Additionally, it would only be necessary to have the light on a small fraction of the time, a fact which could save considerably on power utilization.

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