2017-06-12

With all this extra time on my hands while waiting for the PCB to come back, instead of working on the house, playing with the dog, interacting with family, or doing a push-up I decided to test some of the circuitry I’ve already sent off for fabrication.

The portion of the circuit under test this time was the the over-voltage crowbar circuit. The basic idea is that if the voltage goes above spec, 5.5V for 5V rail, the triac in the circuit is activated and ties the 5V rail to ground which results in, hopefully, a blown fuse rather than a blown micro-controller or some other IC.

In this picture we see the voltage being ramped up by me. That’s the little hump to the left of the reticule centerline. As soon as the voltage hits 5.5 volts the triac activates and the voltage is brought down quick, fast, and in a hurry. At that point the over-current protection in my power supply kicks in and the voltage stays at approximately 3 volts.

This is zoomed in on the moment the triac activates. The over-voltage condition is mitigated in 2 milliseconds.

Very very neat.