I've got a batch of knock-off HC-SR04 ultrasonic sensors from Amazon. They advertise needing 5v and, sure enough, they require 5v. If I give them 3.3v they flip out and can't detect a thing.
But, some eBay ads for these show that they work at 3v, with shorter ranges. Does anyone know if this is true, or just false advertising?
I can order some myself and test them, of course, but if anyone has experience I'd like to save myself the time and money...