Circuits by Tomi

Replacing flashlight bulbs with LEDs

One day I had an old flashlight that had burned light bulb on it. It was a small cheap model powered with two AA batteries. I could fix it with new light bulb, but going through the trouble of trying to find exactly suitable replacement light bulb felt like more than the value of the

TDR kit built

My Time Domain Reflectometer (TDR) circuit has been available as kit made by Far Circuits. The kit consists only of circuit board and components needed to build the circuit in a small plastic bag (you need to download the building instructions). The original circuit design is from my web page and Far Circuits added 5V

TDR circuit kit available

My Time Domain Reflectometer (TDR) circuit is now available in kit form. Far Circuits has made a TDR kit that consists of circuit board and components. The Far Circuits version is a slightly modified circuits, the modification is that the circuit board has a 5V regulator IC in it. With that regulator the circuit power

TDR circuit modification idea

You might know my Time Domain Reflectometer (TDR) signal source circuit published on ePanorama.net many years ago. It has worked well for me many times. Some years ago I made a modification to my own TDR unit. This simple modification allows me to use the same box also as a signal source with a wide

Digital audio isolation

Isolator for digital audio is needed in cases where coaxial S/PDIF digital audio link forms a ground loop in your audio system. Typically in coaxial S/PDIF connections the coaxial cable shield is connected to equipment cases. This arrangement easily creates ground loops which can cause noise problems in various places in audio system. A suitable

Build video isolator

Video isolation transformers are primarily used in CCTV application in fields of security, manufacturing, avionics and display. The video isolation transformer is an extremely broad bandpass 1:1 isolation transformer. Its hum isolation is very good and it can sustain very high noise voltages without degradation. Isolation decreases with increasing noise frequency. Video signals can transformer