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 […]

## jsAllElectronics – Javascript Parts Ordering Script

I wanted a solution for making my visitors easier for them to order parts to build my projects. This code comes from the “Order By Part#” Page. Heres an example of how to use it: Heres the source code of the utility: Real Example

## 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 […]

## Portable DVD player charger cord mod

When I got John zogg’s DVD player it didn’t come with the AC adapter, just the carrying case, battery and the car Cord. At first I thought that it would of charged on 12vdc, but no it has to be 9vdc. So what I did is buy a adjustable voltage regulator, heatsink and a couple […]

## 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 […]