D7 protects against reverse battery connection. The LEDs are biased to operate at about ... They are both inexpensive and BRIGHT! The 12v battery level indicator unit in the photo has no reverse ...

Makers, developers and hobbyists that enjoy building Arduino ... a battery connector & charger built-in, & a fuel gauge that can tell you when to charge the battery.” • Battery Charger Circuit ...

In my example the whole circuitry is powered from a 9V battery ... the circuit and the Arduino Board from the USB cable because the USB port cannot output more than 100mA, that is why you need an ...