New Additions
x86 Instruction Chart
8087 FPU Instruction Chart
9 Volt Battery Chargers
Solid State Circuit Breaker (20V 650mA)
Spice BJT Model Viewer
Ohm's Law Calculator
Prime Factorization
Convert a Decimal Fraction to a Simple Fraction
Example POV-Ray Animation
Example Virtual Machine
Locating a Gunshot with an Array of Microphones
Software Defined Radio
Salt Flats & Aeromods
Audio Amp + Spice References
Image Processing
KFC 'Secret' Recipe
Neddy's Brownies
Ham and Cheese Muffins
Railroad Tracks
The Bike Shed
The Guy That Invented Fire
Mods for the TRS-80 Color Computer

9 Volt Battery Chargers

Pile of batteries, 'That Don't Work'
Collection of batteries that "Don't Work"

Over just a few months, a pile of 9V batteries accumulated. Nothing was known about their status, except "They Don't Work" and that "This is getting expensive".

Some were new, some were old. There were Ni-Cad, NiMH, and rechargeable Akaline.

The LED on the device's charger said the batteries were charged, but reality said different.

I decided to learn to do by doing and ended up building 5 different battery chargers.

Ver 1.0 uses a resistor to limit current.

Ver 2.0 uses a constant current source to limit current.

Ver 3.0 improves on Ver 2.0. (Recommended)

Ver 4.0 uses an op amp and rheostat to provide 0- 16mA of constant current.

Ver 5.0 adds a transistor to Ver 4.0 to increase the current range to 0 - 160mA

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Charge Rate

Wall Warts

Simple 1 Resistor Battery Charger

Constant Current Battery Charger from 2 LED's and a NPN Transistor

9V Battery Charger from 2 NPN Transistors

Adjustable Charge Rate Battery Charger from Op Amp

0 - 160 mA Adjustable Charge Rate Battery Charger

Test Results

741C Cheat Sheet

Sparks and Flames


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