AMB Laboratories DIY Audio

[linux-works]

inspired by these articles:

http://hackaday.com/2010/11/30/unlockin ... ultimeter/

http://translate.google.com/translate?h ... 2Fnode%2F8

http://flashingleds.wordpress.com/2010/ ... ultimeter/

http://blog.felipebarriga.cl/diy/cheap- ... ent-page-1


the '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.

[linux-works]

demo shot with transmitter and receiver 'talking'. the green led is on showing that data is really coming thru the light connection.



the small red board is an FTDI adapter, same as the infamous $20 cable for aduino software download.

here's the qt-dmm app setup for linux showing the magic port settings you need to manually configure (I then saved that profile as 'vc99'):

[helzerr]

Thanks for sharing this - I may be hacking my DMM later

[linux-works]

partial schematic for VC99:




I followed their guide almost exactly. d8, d9 and the rest of the connected parts are what you care about.

a better version would be to have a transistor drive several of the LEDs and better yet to have them 38khz-carried.