Infrared LED connector for Voltcraft multimeter

thingiverse

This thing holds a 5 mm LED to the optical transmitter of our Voltcraft VC850 digital multimeter. It should be compatible with VC820, VC830, VC840, VC850, VC870, VC920, VC940, VC960. It might even work for the corresponding UNI-T DMMs. I am using an infrared LED which I salvaged from an old IR remote control to receive the signal. With two N-MOSFETs and a UART to USB adapter I send the data to my PC. A LM324 OpAmp works as well. I didn't know which is “better” and I was curious, so I tried both. Leave a comment if you feel like educating me. :) The VC850 transmits frames of 14 bytes roughly every second @ 2400 bps 8N1. The protocol is described in chapter 13 of the FS9922-DMM4 datasheet. The only exception I found was the diode test which is on Z1 `(sb2 & (1<<7))` for the VC850 rather than on `(sb3 & (1<<2))`. This thing just holds an LED so that I have my hands free. I'm sure some people here are able to squeeze the entire circuit into such a connector. That wasn't my goal. But feel free to create a cool remix if you can. OpenSCAD files are included. Have fun! :)