I have a project in which we want to place a proximity sensor inside/ on the bottom of a tapered spring in order to track the compression of a plastic material on top of the spring. The distance range would only be 1-10 cm away from the sensor and the plastic would be compressed 80-200 times/minute. We were thinking ultrasound (but the waves bouncing off of the spring may be a problem) or an IR emitter/detector system. Are there any other suggestions or examples of similar devices that can accurately measure the distance from the sensor to the plastic and the rate of movement (compression/minute). Thanks.
Electronic – Short Range Proximity Sensor
proximity-sensor
Related Solutions
Mouser's latest mailing mentioned this one: Vishay VCNL4000. For the price of the proximity sensor you also get an ambient light sensor. 4mm x 4mm, 0.75mm high, though it has three blobs on it which make it somewhat higher. Still looks like it's less than 3mm.
Detection range for the proximity sensor is only 20cm, though.
disclaimer: the mention of Mouser is not a shopping advice :-)
Pretty sure they use radar for adaptive cruise control in cars. Check this sensor out:
I've heard them called "headway sensors" or "radar headway sensors". There are other technologies like acoustic but I'm not sure if they'll have the range you're looking for. Laser could work but it's aim is pretty narrow, dust dirt and fog can get in the way etc.
Good Luck!
Best Answer
You could wind a coil around a former and then mount a plunger to the spring so that as the spring went up and down the plunger would move in and out of the coil, changing its inductance.
Build an oscillator around the coil, use the zero-crossings to drive a one-shot, integrate the one-shot's output pulses and voilà!, frequency-to-voltage converter.