inspired by these articles:http://hackaday.com/2010/11/30/unlockin ... ultimeter/http://translate.google.com/translate?h ... 2Fnode%2F8http://flashingleds.wordpress.com/2010/ ... ultimeter/http://blog.felipebarriga.cl/diy/cheap- ... ent-page-1the 'tl;dr' version
: many meters have chipsets inside that already include rs232 serial data out. tap the wire, run it to an optoisolator and run the free linux 'qt-dmm' software for data logging. this meter costed me $30.
I located a VC99 or two and started hacking one (or two) for myself
some photos of the experience:
press and hold the REL button and rs232 appears on the display and the data stream starts. press/hold again to cancel.
I do have the IR receiver working, but no interesting photos of it yet. its simply a phototransistor, a single resistor from collector to Vcc, emitter to gnd and collector to RX-data. I used the FTDI data cable we use for the arduino.
the blue wire-wrap wire is data-out from the chip and white wire is Vcc. those will eventually go to an IR emitter LED or better yet, a 38khz modulator so that the signal can be 'seen' from across the room just like consumer IR handheld remotes. I will be able to use the regular TSOP IR receiver we use for the arduino, then; but I need to modulate the 2400 baud TTL signaling on 38k for better IR sending and decoding.
with a simple DC signaling and no 38k fanciness I can get about 4" of distance between the IR sender and a phototransistor. workable but hoping the full 38khz version will be even better.