Felipe Barriga Richards Blog

After buying this DMM (VICHY VC99) (32.98 USD) I was curious to see what can be hacked so I open it. After removing all the parts I found below the LCD the IC that control this device: FS9922-DMM4. After searching for cool stuff in the datasheet I realize that it can output the LCD data trough a serial port. The datasheet contains an example of how to make this output serial port using an IR led to insulate the computer from the DMM.

Here is the schematic (Transistor: 2N3906; LED: IR204):

DMM Circuit Scheme

Alkaline batteries can leak and start a corrosive process. When this occur it start to damage all metal parts of the circuits if you don’t stop it in time.
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Upgrading Jetech LXM-500 UPS
After finding this old UPS I’ve decided to upgrade it with a 12V 55A car battery (the original battery was a 12V 5A).
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