This is a simple yet effective resistor decade box. The resistors are connected in parallel with the SPDT/SPST switches. The resistance is the sum of all switches opened(NOT CLOSED!). When resistors are in series the resistances add up. $$Rt=R1+R2+R3$$ And when they are in parallel the total resistance decreases: $$Rt=\frac{1}{\frac{1}{R1}+\frac{1}{R2}+\frac{1}{R3}}$$ Rt is the total resistance […]

## Simple Plasma Speaker/HV Power Supply

This circuit takes 3.7vdc and converts it to about 18kv. The transistor is used for the plasma speaker. It’s basically a Single-Ended Class A Audio Amplifier. The 500-ohm pot adjusts the voltage sent to the converter. The pot must NOT go over 500 ohms because then the voltage could be too high. The circuit is […]

## Unocharge NiMh battery charger

Here is my plan for John Zogg’s battery charger. It uses 3 analog inputs for each battery cell. I decided to use this one that flyback found on the internet is because it can turn off when it is done. It has a temperature sensor. It uses an Arduino Uno to control it. USB is […]

## NiMH and NiCD battery charger

Here is a simple transistor battery charger it can charge batteries up to 12v in series. It has an LED and a few parts. To use it you must decide on a power supply voltage, current limit resistor, and number of cells. First to figure out what voltage to use you must know the total […]

## 8-bit Capacitance box

Today I began working on my Capacitor box. It’s value is in binary obtain from switches. If you can’t get perfect Capacitance from each switch you can use multiple in parallel or series. For capacitors in series the value is: $$Ct=\frac{1}{\frac{1}{C1}+\frac{1}{C2}}$$ Both equations can have any amount of capacitors the variable Ct is the total […]

## Diy Cigarette lighter extension cord

This do-it-yourself extension cord is simple and straight forward. The reason! Why I built it was to make my cell phone reach the outlet. I just used 2 strains of wires connected to both ends. The one I built has 3 different kinds of wires. This is because I wanted to build it out of […]

## Arduino Binary Clock

This is a simple Arduino Binary Clock. It comes with a program that generates the script and uploads it to the arduino board. Part of the code isn’t mine only the part that allows you to get the time from the computer and configure the script to use it. You can download the script maker […]

## DIY Powersupply

This power supply is easy to build and fun to make. It will have 2 meters 1 for voltage and 1 for current. They will both be DC voltmeters, for the amp meter we will use a shunt resistor. Here’s the part list: Qty Name All Electronics Cat# Sub-total total 1 LM317T Adjustable regulator LM317T […]

## PN Junction tester

This transistor tester tests bipolar junction transistors junctions. It tests the junctions for open and short circuits. It uses 4 resistors, 4 LEDs and 1 SPDT switch. A good transistor will only have 2 out of 4 LEDs lit, on one side of the switch and 4 on the other. You can also test standard […]

## Android Scope Probe

This useful cord can allow an Android Phone/Tablet to be used as an osciloscope. All you need is the 4-pole 3.5mm jack to 3 rca cable. The cord will need to be modified and be tested with an resistance meter, so you can figure out which wire goes where. NOTE: EVERY CORD IS DIFFERNET! Also […]