Friday, August 3, 2012
UPDATE (9/12/11): When actually implementing the circuit in my laser project, I uncovered several problems. I was going to have the output connected to a voltage regulator inhibit pin. Because the datasheet was so vague, I thought that the regulator was off when that pin is high. I was wrong. I had to place a mosfet on the output to invert the signal. Doing that caused another problem. The opamp's output voltage was too high (~2.5v) in the off state causing the mosfet to stay on. I had to increase the resistance on the feedback which also required that I change the resistor for the zener diode. Note that different opamps can behave very differently based on their specifications. Be sure to use the same opamp in your final build as the one you used for testing. LTSpice schematic files can be found on my blog: patheticcomputing.com In this video, I explore several different circuits and solutions to the problem of low battery voltage cutoff. I also explain zener diodes, Schmitt triggers, and hysteresis. Near the end of the video, I show an actual breadboarded circuit and show how to find the correct resistor values through experimentation.
http://www.youtube.com/watch?v=E6Zkq9tV6Lw&hl=en
