low battery indicator circuit
this is a very usefull circuit if you're building projects powered by batteries.this simple circuit informs you when the battery needs to be recharged by turning on a led.the threshold is set to the desired voltage by a multiturn potentiometer. the only thing you should have in mind is that it doesnt work with red led's,at least with the ones i tryied. i think it has something to do with the very low voltage that red led's need to lit.didnt have the time to experiment further.besides that,the circuit works perfect. components needed: R1= 1k (2,2k if you use smd led) R2= 2.2K U2= TL431 adjustable shunt regulator(can be found very easy in power supplies) PR1=10K potentiometer (for higher precision use multiturn) LED1= led (not red-didnt work with me) here is a video building it.