When working around mains voltages, it can be useful to know whether a given circuit is live or not. While this can be done by direct connection with a multimeter, non-contact methods are available ...

In this video I’m showing how I’ve built a very simple battery backup circuit for my home alarm system. The circuit charges a 12v lead acid battery and in an event of a power loss, it transfers the ...

Have you ever needed to power a 12-volt relay in a circuit but only had 6 or 9 volts available? This simple circuit will solve that problem. It allows 12-volt relays to be operated from 6 or 9 volts, ...

It is a running gag around here that whenever a project posts, someone will inevitably point out that it could have been done ...

Most circuits that require current loss detection use expensive isolation amplifiers. This circuit solves that problem with a simple and low-cost method to detect current loss of 4-20 mA. To view the ...

This circuit is suitable in every situation where over-current protection is required. Here we give an example from the model train world. Every seasoned model train enthusiast knows that there is ...

Early radio receivers and record players nearly always had a knob marked “tone,” which was usually a crude low-pass filter with some form of severity adjustment. At best, these controls could ...

All circuits, analog or digital, have characteristics dependent on the values of their component parts. Invariably, these parts are non-ideal in many ways. Even their most fundamental characteristics, ...