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By OliverNZ
#71709 Hi all,

I'm trying to trigger a GPIO on an ESP8266 when something moves past in about a 4-5m range (e.g. car). So I thought about using an ultrasonic sensor but the distance while rated at 4m probably is limited to about 2m. IR/laser range sensors are about 1m exact. I have nothing that could reflect the signal on the other side. I can't use anything mechanical (i.e. ground based sensor). And I need it to be fast to trigger (within 50ms).

Any ideas out there of things I could use? Potentially I could have something reflecting a beam but that would need to be at least 5m away.

Cheers & Thanks!
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By rudy
#71720 Microwave radar sensor with a dish to reduce the beamwidth would something to investigate. It will do it but the problem is what components can you use that will meet your time requirements and is affordable. I have used the cheap $1 sensor boards and am quite impressed with them. I have not tried something on the lines of what you want to do.

I have lots of experience with an ultrasonic sensor that SensComp/Polaroid made. I spent hundreds of hours trying to make the technology work well in feed bins. (I call it the project from hell) I recommend you don't waste your time looking at that. It might do the 50mS. The problem is that the target needs to be perpendicular to the path of the sensor. Depending on the angle you could get no reflected signal back.

Laser beam that would be interrupted (laser on the far side) would be the best bet if you were able to have a device on the other side. But you can't so no go.