DIY: hacking multimeters for RS232 data logging output

Use this area for DIY topics not related specifically to AMB projects.

DIY: hacking multimeters for RS232 data logging output

Postby linux-works » June 30th, 2011, 9:07 pm

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:

Image

Image

Image

Image

Image

Image

Image

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.
Last edited by linux-works on July 1st, 2011, 10:26 am, edited 1 time in total.
Sercona Audio (Control Systems for Analog and Digital)
Photos: http://www.flickr.com/photos/linux-works/
User avatar
linux-works
 
Posts: 1962
Likes: 0 post
Liked in: 27 posts
Joined: March 31st, 2010, 9:04 am
Location: Santa Clara, CA
Country: United States (us)

Re: DIY: hacking multimeters for RS232 data logging output

Postby linux-works » June 30th, 2011, 10:12 pm

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

Image

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'):

Image
Sercona Audio (Control Systems for Analog and Digital)
Photos: http://www.flickr.com/photos/linux-works/
User avatar
linux-works
 
Posts: 1962
Likes: 0 post
Liked in: 27 posts
Joined: March 31st, 2010, 9:04 am
Location: Santa Clara, CA
Country: United States (us)

Re: DIY: hacking multimeters for RS232 data logging output

Postby helzerr » July 1st, 2011, 5:14 am

Thanks for sharing this - I may be hacking my DMM later ;-)
User avatar
helzerr
 
Posts: 67
Likes: 87 posts
Liked in: 2 posts
Joined: April 2nd, 2010, 9:42 am
Location: Orlando, FL
Country: United States (us)

Re: DIY: hacking multimeters for RS232 data logging output

Postby linux-works » July 1st, 2011, 12:36 pm

partial schematic for VC99:


Image

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.
Sercona Audio (Control Systems for Analog and Digital)
Photos: http://www.flickr.com/photos/linux-works/
User avatar
linux-works
 
Posts: 1962
Likes: 0 post
Liked in: 27 posts
Joined: March 31st, 2010, 9:04 am
Location: Santa Clara, CA
Country: United States (us)

Re: DIY: hacking multimeters for RS232 data logging output

Postby jhgorse » December 11th, 2013, 1:12 pm

linux-works,

What parts did you use for D8 and D9?

Cheers,
Joe
jhgorse
 
Posts: 1
Likes: 0 post
Liked in: 0 post
Joined: December 11th, 2013, 1:10 pm
Location: Ohio
Country: United States (us)

Re: DIY: hacking multimeters for RS232 data logging output

Postby linux-works » December 12th, 2013, 9:45 am

its been a while since I looked at that, but I used nothing special for parts. even a radio shack ir transmitter led was ok and some generic photo transistor (collector and emitter only, base is open, iirc). I was not able to get very much range, but the proper way is to modulate the signal on top of 38khz or similar (which is a common freq for handheld ir remote controls).
Sercona Audio (Control Systems for Analog and Digital)
Photos: http://www.flickr.com/photos/linux-works/
User avatar
linux-works
 
Posts: 1962
Likes: 0 post
Liked in: 27 posts
Joined: March 31st, 2010, 9:04 am
Location: Santa Clara, CA
Country: United States (us)


Return to General DIY discussions

Who is online

Users browsing this forum: No registered users and 0 guests

Quick Links

AMB audio DIY resources
AMB audio shop