Misc power circuit diagrams

Logic PSU with Overvoltage Protection

A simple 5 Volt regulated PSU featuring overvoltage protection.


Following a hunch, the author discovered (or re-discovered?) that all plants carry an electric charge relative to the ground. This charge is more or less constant regardless of the size of the plant - a kind of "background voltage" in nature.

Power Failure Alarm

This is a very basic alarm designed to let you know when the electricity supply fails. The alarm is powered from a battery which uses no current consumption at all in standby, a battery should therefore last its full shelf life.

Fast Electronic Fuse

A fast electronic fuse designed to operate on 230V AC with an adjustable trip current.

Power Outage Warning

5 to 15V supply - LED indicator. Adjustable time detection

Broken Charger-connection Alert

Detects if a device is not properly connected to its supply Suitable for battery chargers, portable appliance supplies etc.

Under Voltage Circuit

This under voltage circuit may be used as an add-on to an existing power supply or standalone. The circuit draws power from an existing power supply, which may be up to 36 Vdc. Once voltage drops below a preset level the output swings high. A CA3140 MOSFET op-amp is used as a comparator, the output can drive loads of up to 10mA so can drive a low current LED directly. Additional buffering is required for higher loads.

Overvoltage Protection for the LM317

This is an add-on Over Voltage Circuit for the LM317 Regulator Circuit submitted by Matthew Hewson.

Digital Remote Thermometer

Remote sensor sends data via mains supply Temperature range: 00.0 to 99.9 °C

Self-powered Fast Battery-Tester

Tests 1.5 to 15 Volt cells Two-LED display, no power supply required