Infrared LED connector for Voltcraft multimeter

thingiverse

This device attaches a 5 mm LED to the optical receiver of our Voltcraft VC850 digital multimeter. It should be compatible with VC820, VC830, VC840, VC850, VC870, VC920, VC940, and VC960. It may even work for corresponding UNI-T DMMs. Using an infrared LED salvaged from an old IR remote control to receive the signal, I send data to my PC via two N-MOSFETs and a UART to USB adapter. A LM324 OpAmp also works well. I wasn't sure which was better, so I tried both. Please share your thoughts if you'd like to educate me. The VC850 transmits frames of approximately 14 bytes every second at 2400 bps 8N1. The protocol is described in chapter 13 of the FS9922-DMM4 datasheet. One exception found was the diode test, which is on Z1 `(sb2 & (1<<7))` for the VC850 instead of `(sb3 & (1<<2))`. This device simply holds an LED so I can keep my hands free. Some people here may be able to fit this entire circuit into a connector, but that wasn't my goal. Feel free to create your own remix if you're up for the challenge. OpenSCAD files are included. Have fun!