Circuits by Tomi

XLR mic cable tester

I saw presentation of Sound Tools XLR Sniffer/Sender at It was described: “Quickly troubleshoot faulty mic lines and cables with this set of remote end cable testers. The XLR Sniffers can also utilize phantom power to test snake lines and cables in live environments, making it simple to diagnose issues and get your show

Passive summing mixer

For a passive summing mixer is a circuit to combine two audio signals to one signal. Passive summing works generally ok, both with unbalanced and balanced circuits if all connected circuits are same type (mixed balaced and unbalanced is mixed business if it works as wanted or not). When the devices connected to all inputs

PoE Powered Christmas Lights

Found some broken LED christmas lights (operated originally from 24V transformer) and a suitable spare switch mode power supply (36-72V to 24V). Then I got an idea to combine them to an experimental PoE Christmas light project. Circuit diagram: The circuit operation: Initially circuit presents around 23 kohms impedance when low voltage is on line

My DIY lab power supply

An adjustable regulated power supply is a necessary tool for an electronics laboratory. Here is a laboratory power supply 2.7-30V up to 4A I built has worked for 30 years ago and still going strong. Its function is to supply a stable voltage set by the voltage control potentiometer up to the current set by

VGA to SCART adapters

Some time ago I saw  The ultimate VGA to SCART adapter project at Hackaday with description: Accurate recreation of vintage arcades is becoming increasingly difficult. CRT monitors are rare nowadays and, even if you find one, it will probably not support the 15.7Khz horizontal frequency used by many old arcades. A good alternative is a

Enttec Open DMX DIY

DMX512 (Digital Multiplex) is a standard for digital communication networks that are commonly used to control stage lighting and effects. It was originally intended as a standardized method for controlling light dimmers up to 512 dimming channels. The first standard version was created in 1986, with subsequent revisions in 1990 leading to USITT DMX512/1990, ANSI