Don't know if I can post this sort of thing here - apologies if it is not permitted/in the wrong place! But just for fun I'm trying to build a light-activated buzzer. Function: Light goes on, voltage at the divider of the first circuit passes threshold for Schmitt trigger (U1), causes trigger to go high and activate the transistor/relay (Q1), which closes the second circuit and causes the buzzer (R4) to go off - the buzzer should keep making noise until the system is reset. Questions: Will it work the way I expect it to? Will Q1 explode with a setup like this? (Or can I get a Schmitt Trigger thingy that regulates the current...?) Can I use one battery to power both circuits, or will I need to use 2? Attached is the circuit diagram - unfortunately I couldn't find the symbols I wanted, so here is a legend (also reproduced in the image) R1: Photoresistor R2: Variable resistor (to make adjustments for light) R3: Variable resistor (to make adjustments for the resistance of the buzzer) R4: Buzzer U1: Schmitt Trigger* Q1: Transistor/relay (activated/deactivated by the Schmitt Trigger) *Not sure how to get one of these... I found a 7419 chip that functions as a Schmitt Inverter or something - can I just use one of these?