ultrasonic range finder.

[Woody]

I am new here and somewhat new to electronics. I am able to solder components together and understand how to read a schematic but I still have faith in the magic smoke theory. My current problem is trying to get an ultrasonic range detector to operate without an arduino. Is there a simple circuit I can use to get module HC-SR04 to operate a buzzer or vibrator?

[MJG]

So you want to use the range finder module to detect an echo and don't really care about the range?

You have four pins on the module. One is +V, one is Ground, one is the Trigger, and one is the Echo. I got this from the HC-SR04 User's Manual (from https://docs.google.com/document/d/1Y-yZnNhMYy7rwhAgyL_pfa39RsB-x2qR4vP8saG73rE/edit?pli=1#).

You can trigger a burst of ultrasonic pulses by pulling the Trigger pin high. You can use a momentary N.O. pushbutton, methinks. The only caveat is that the minimum Trigger signal has to be a minimum of 10uS, but a human pushing a button would find it hard/impossible to press and release any quicker -- so no worries there.

Your only problem will be the Echo coming back. It can be very short as well and you might not hear it if you hooked up directly to a buzzer. So what you need is a pulse-stretcher that will detect the super-short echo pulse and stretch it so that the buzzer goes off long enough for you to hear it. The internet is full of pulse-stretchers using the good old 555 timer. Do a search on "555 pulse stretcher." The circuit is also sometimes called a one-shot or monostable circuit.

The circuit requires a low signal, while the Echo pin goes high, so you'll need to invert the logic. You can use an inverter chip or a transistor for that task.

I am not handing you the circuit on a silver platter. You'll need to dig a little yourself. If you get stuck, post again.

Of course, all this is based on my assumption that you want an "object detector" rather than a range finder. I could have misunderstood completely...

W