Looking for practical Arduino projects? This guide shows how to control a relay from your smartphone using an Arduino Uno — ...

Relays continue to be useful and popular, but in low-power, battery operated applications they tend to be power wasters. The following relay economy circuits reduce coil power significantly by simply ...

1. The well-established relay-driving circuit uses an optocoupler to isolate the grounds and noise coupling between the low-voltage digital-control signal circuit (left) and the relay as load (right).