## Audio over telephone

Heres a simple circuit that takes a audio signal(from ham radios,computers or cd players) and converts them into a telephone signal. It powers the phone line with 22vdc(It doesn’t have to be 22vdc, different voltage means different resistor is needed). The phones can run as high as 48v. If you use cordless phones the converter …

## DIY cable tester

In this blog I will show you two ways to make a cable tester. The 1st way uses a arduino (software controlled). The 2nd way uses a decade counter chip(CD4017) and a flashing LED. I am going to order the Dual RJ45 jack to screw terminals from eBay. The other connectors are from parts-express. I …

## 6AL5 low voltage logic circuit

In this blog we will experiment with vacuum tube logic gates. We will be using low voltage so it is totally safe. We will use a 6al5 twin diode tube. In the circuit below shows how to use it as semiconductors diodes but it’s very same as for vacuum tubes. Simply wire positive and negative …

## Capacitance substitution board

In this blog I will show you how to make a dip switches capacitor substitution board. Its very simple since capacitors add up in parallel. So if you look at the schematic you will get an idea.

## Simple doorbell/alarm

This is probably the simplest doorbell or alarm circuit that is out there. The buzzer will not be constantly on since the buzzer gets switched on by a capacitor. The circuit draws hardly anything when off as you will see in the graph below. As the capacitor gets charged its current lowers down a lot. …

## Arduino Video poker for the TV

Here is a project I have been working on. It hooks up to the tv and allows you to play 5 different types of video poker games. The game is in black and white and some of the suits look funny. The pinouts can be found in README.MD file. Youtube videos

## Serial Port PWM

In this blog I will show you how to generate pwm with a computer with a serial port. This tool was originally written by subcooledheatpump from YouTube. I made it better where you can choose which com port to use(by command-line or by being prompted to do so). Controlling it is now better since now …

## The simplest in-circuit transistor tester

This is the simplest in circuit transistor tester. It uses two ammeters to measure the transistor gain. It is kinda like the heathkit IT-18 one but uses 2 meters instead of one. I plan on using relays for the polarity switch instead of a 5PDT Rotary switch. It uses a LM317 regulator for providing a …

## Discrete transistor op amp

Here in this blog i will show you how to build a high powered transistor opamp. The design is based off of allaboutcircuits.com design. The only changes were the transistors were power transistors and rprg is lowered to 390 ohms half watt.

## Capacitor powered LED flashlight

Long time ago QVC sold a shakeable Flashlight that had no batteries just a shakeable generator and a super capacitor. This flashlight uses a 5vdc 1.5a wall wart to charge the capacitors. To figure out how long it will take to charge the flashlight you use this equation $$T=5R_{currentlimit}C$$ And for total discharge time $$T=5R_{LED}C$$ …