I am trying to make a time of flight sensor using a pair of piezoelectric crystals, a Schmidt trigger, and an atmega328 timer using a single timer capture interrupt. I have attached a picture of my scope with about a 200mV trigger. Note the time response seems pretty long given a 675kHz crystal... 10 ms means I would need an incredibly long pair of sensors. For this concept to work, I would need a sensor response of about 10 us!
I took a disk: Mini Piezo Ceramic Disc 3x0.4mm S 675 KHz - SMD03T04S311 - STEMINC - Piezoceramic Discs, Plates, Transformers, Bimorphs and Cylinders. I soldered wires to the top and bottom and mounted wires to a tripod such that the piezo was levitating by about 2 inches of 22 gage wire. I would fire a projectile above the sensor. I think I am only detecting the movement of the sensor relative to wire strain and not the compression from the shockwave. Oscope does 100mHz samples.
I don't think I am "mounting" the crystal properly. Maybe I need a more rigid mounting surface? Does anybody have experience making a piezoelectric sensor from scratch with very high frequency response? I know this can be done.
