Low-battery indicator circuit

I designed this little circuit to show a battery’s status.

It lights an led to show the battery is OK, and will change to show another colour when the battery’s low.

The transistors can be any npn-type, and the leds can be any colour (in the diagram, green=ok, red=low)

The operating voltage range is ~3v-12v, and by adjusting the resistor values it will work beyond that.

The voltage the low led comes on at, is set by the potentiometer.

Momentary latching circuit

Here is a little circuit I made that will allow a momentary switch to turn on/off a load.

Q1 can be any NPN transistor, and Q2 is any N-channel MOSFET capable of handling the current being switched. It should be fine with a range of ~5-12V but I've only tested it at 7.4V.

It somewhat mimics the action of a newer console's power button. I made it so I could switch a relatively large amount of power with a small tactile switch, press for on, press again for off.