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HI , I'm an extreme novice and want to make a salvaged PIR+ relay +windscreen pump,squirting device.

HI everybody, i followed this instructablehttps://www.instructables.com/id/Re-purposing-an-Air-Wick-Freshmatic-Compact-i-Moti/step4/Aproach-1B-Digitized-Sensor-Output-Small-Module/           and the pir is outputting +-4.7 v. i purchased a rs5 5v (coil) 12v switch relay. I have connected the output of the PIR to the relay coil and i am trying to use this to switch on a 12v windscreen washer pump. I can switch the relay with 3x 1.5v cells directly and the pump activates but when i use the output of the PIR to try and switch the relay, nothing happens. I am assuming it is a ( Icurrent ) problem but as i say I dont have a clue.please help.?

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You need to add a transistor to turn the relay on, the PIR won't have enough drive capability.
You know, that board had what looked like a pretty beefy lookin' transistor on it. I mean it did back in Step 2. I am guessing that was there for driving the actuator for the can of air-fragrancer. Without speculating on how that transistor was driven, how much current it could handle, how often fragrance-squirter actually turns on, I'm just saying that there was a freebie transistor of some kind that came with the board, and maybe it could be pressed into service in some other way, like driving a relay.
Hey... it looks like the author, Doug Paradis, already did something to exploit that transistor. Look at the circuit diagram picured in Step 10.  It's the one with an input labeled "R", what looks like a nice relay driving circuit.
macgyverknife (author) 6 years ago
thanks for the quick and helpful responses. Jack, unfortunately i didn't spot that option in step 10 and had already chosen to cut the board down as in step 4.(should have read the whole thing) I have used the transistor and diode that i removed from the board. Following Steve's advice and after some reading it is all up and running and my wife has just received a blast of cold water. thanks guys.
Looks to me, as Jack notes, you have everything in place there anyway. I would say you link pin D and pin R together and connect your relay on the white connector.

Steve