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 …
Author Archives: Justin Roeder
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 …
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 …
DelpFo information app
This app draws text on the top left corner of the screen. It has UTC Time, Uptime, last IRC Channel message in mIRC, Error Of The Day, Memory Load, IP Addresses and Phase Of The Moon. It’s lightweight and open source.
Fixing a golf cart charger
When I went for a host home visit Gary left the charger out in the rain. And now it won’t turn on. All four fuses were ok. The output of the charger was zero. The charger is really expensive because of the voltage output being 35 volt at 20 amps. building it is really hard …
Circuit Simulator