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How to use a motion sensor to trigger sound? Answered

Hey guys, I initially posted this in the forums but someone suggested I put it here.

I'm trying to trigger audio with a PIR sensor but with no joy. I was hoping that someone on here would be able to help!

I've got:
Oomlout SPD61 PIR sensor
Omron 5v relay g6a-234-bs
Voice recorder Cebek C9701
5v Voltage regulator L7805CV

with 9v battery attached and 8ohm speaker (these both work fine).

This is loosely based on the following instructable https://www.instructables.com/id/Sound-graffiti/

But the instructions relating to the wiring was not very detailed. 

Some people have suggested that I would also need a transistor between the sensor and the 5v relay (which was not mentioned in the instructable), can anyone confirm this?

If anyone could draw me a diagram of how I'm supposed to connect the sensor to the relay to the voice recorder I would be so grateful!!

Dolly x



Best Answer 5 years ago

According to the datasheet for that sensor, is that it either drives the output high/low OR has open collector output. Open collector means it cannot drive the output high to 3 or 5 volts, but in fact can only pull the output down to ground 0 volts. What does that mean? It means it basically only outputs signal level output (very low power). basically if you want to control anything you have to buffer it with something like an NPN bipolar transistor.

On page 2 of the pdf linked it shows a circuit diagram using a relay and a transistor so when motion is detected, the relay can toggle your audio circuit.

Dolly Mix

5 years ago

Thanks Frollard! Your explanation is really helpful, especially for a noob like me!