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Junior's got a drinking problem.

Junior's my cat, and he only drinks from running water.

Pet water fountain pumps are USB power driven (good), but noisy (30db w/ wavering pitch almost, not quite, at C3) and the noise is irritating. So, I want a Junior-detector that completes a 5VDC circuit to deliver 200mA to the pump only when Junior (8 lb house cat) approaches within 12" of the fountain.

The proximity detector should use infrared (I think) so there's no problem with noise Junior could hear, so the device should include an IR LED to illuminate Junior.

Decades ago, I'd pull something out of a Lafayette Radio or Radio Shack catalog and breadboard it, but the former is long gone, and the latter wants to sell me an Arduino-based solution, which is spendy overkill.

A web search found this 5VDC infrared light-sensor-switch combination with 80cm range, but it only passes 100mA, and I need 200mA to drive the water fountain pump.

Is there some better way to simply do this? I really like the idea of one component to handle the illumination, detection, and switching, but it must switch 200mA at 5VDC from that USB wall wart which powers the fountain pump.

JYelton
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K7AAY
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    I really like this question and how you've stated it, but sadly, upon reaching the end, you're asking for a component or vendor recommendation, which is off-topic. You might consider re-wording it a bit. Instead of asking for help finding a switch, instead try "I tried this switch which can only handle 100 mA, is there some better way to do it?" – JYelton Apr 21 '22 at 22:37
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    What about using the existing signal to turn on a transistor, which will then pass the required current? Lots of microcontroller based motor circuits out there. I've got a small usb fan that uses an A1SHB or A2SHB mosfet to supply far more current than the tiny uController can source. – enhzflep Apr 21 '22 at 22:41
  • Maybe have a look at passive infrared sensors, like they use in burglar alarms. – user253751 Apr 22 '22 at 09:44
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    RFID tag on the collar springs to mind. – Neil_UK Apr 22 '22 at 12:53
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    Oh btw. since you are dealing with a cat, he will find a way to not make it work. Like not even approaching that thing from afar when water is not running ;) – PlasmaHH Apr 22 '22 at 15:39
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    As a slight frame challenge, if the pump noise is too loud, I'd look for a quieter pump (and maybe build my own fountain around it). If the noise is annoying you now, imagine how much _more_ annoying it will get when it's not constant but intermittent. – Ilmari Karonen Apr 22 '22 at 18:58
  • Arduino costs $5 or less if clone used and once you start using them they become an extremely useful tool. – Russell McMahon Apr 26 '22 at 23:04

3 Answers3

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Use the sensor you found, and drive a small relay with a coil current of under 100 mA (basically any common small relay), to turn on the device/pump.

Alternatively use any number of PIR motion sensing modules with a built in relay. Reduce false triggering by adding a tube around the sensor to narrow the field of view. Or skip the middle man, a usb pir motion sensor that has usb connectors on both sides.

Passerby
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  • Have not found USB PIR motion sensors w/ simple switching & USB connectors. That would be perfect, if you know of any. – K7AAY Apr 21 '22 at 22:45
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    Did you try "usb motion sensor" in google? – Passerby Apr 21 '22 at 22:59
  • Passerby, your search phrase hit the nail on the head! Please submit that as an answer so I may accept it! – K7AAY Apr 21 '22 at 23:33
  • @K7AAY wiring up a USB connector is not difficult especially if you only need the power. You can literally cut a USB cable in half and strip the ends. – user253751 Apr 22 '22 at 13:54
  • @K7AAY You will definitely need [flyback diodes](https://electronics.stackexchange.com/questions/110574/how-to-choose-a-flyback-diode-for-a-relay): one across the relay coil (to protect the sensor) and one across the motor (to protect the relay contacts). – Andrew Morton Apr 22 '22 at 19:03
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I think, thin plywood or plastic platform right in front of fountain, staying on three legs, one of which is a switch with proper return spring, will solve the problem :-)

Vladimir
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A retroreflective infrared sensor and an electromagnetic relay would do.

enter image description here

Here's the schematic.

enter image description here

The sensor shown has an open-collector output.

The 'NO' contact of the relay is to be used to energise the pump.

vu2nan
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