It’s a project called snapVCC, and it turns a 9 volt battery into a regulated 3.3 or 5 volt supply. The idea behind snapVCC is simple enough; just add a circuit board to the top of a nine volt ...

This is a very simple 9V low battery indicator circuit which has 2 LEDs, one green which will light up when the battery voltage is higher than 6.9 volts and one red LED which will light up when the ...

If you have trouble getting any of these parts to stay in place, use a scrap of aluminum foil to bridge any gaps. On a large phone with a fast-charging charger, the 9 volt battery may have trouble ...

The whole circuit, complete with tiny speaker and an LED to indicate pulses, sits neatly on top of a 9-volt battery. The video below shows it in action with a test source.

Buying a 9-volt battery is now the simplest way to upgrade your home to a smart home. The Roost Smart Battery for smoke alarms and carbon monoxide detectors is now available to pre-order for ...