Making automated measurements - Page 1
Forum section: electronics / testgear

author: justinDavidow
author_rank: Newbie
timestamp: March 02, 2015, 05:54:51 am
content: Hi Everyone! (first post! been a long time reader / viewer, but only recently had time to get into personal hobby electronics)I'm looking for ideas, I'm interested in and working on various solar lighting solutions (nothing really exotic; solar + wind + water generation, various power harvesting, storage, and transmission to various lighting solutions for city dwelling + rural folks in my neck of the woods. (Manitoba Canada)I've been designing and building simple little low voltage PWM controllers to efficiently drive LED's, but at present have no "good" way to characterize my changes in terms of output light.I'm an automator at heart. I love making things work together; and I love getting all the pieces in place to get useful data from automated measurements. Most of the testing I do isWrite a script of operating parameters (input ranges/extremes, devices that need temperatures collected, etc)Setup various instruments for measurementsTrial run to sanity checkRun full tests (10 minutes to days at a time)Process dataRework designOne thing I've never been happy with is my measurements regarding light output. I've considered building a test apparatus; a scale model maybe a square 100mm with a grid of CdS sensors to collect data about the intensity and the fall pattern. This would likely be alright; but it's far from ideal. (I'm a Hobbiest; most of the work I do with electronics these days is just favors for friends or the odd troubleshooting job for an old client)At the moment, I'm simply:Rigging a CdS cell at the end of mat-black (ish) cardboard lined tube (~20cm ish from DUT to sensor)Inserting the LED and taking a reading for "background"Feeding straight DC power, current limited to the device's rated operating maximumRecord the min value at maximum light outputDisconnect LED from power supply and reconnect to driver circuitPerform automated testing with relative resistance from the minimum valueAnyone have any good ideas on characterizing light output of various LED's under various operating conditions (any form of sensors or test jigs anyone have information on?)I'd also like to better profile and calibrate my photocells; I've tried looking around online but have not really found a good resource. Anyone have some good reading on how I (as a hobbyist) might be able to calibrate a photocell against various lux levels to get repeatable + consistent "lux" output measurements for dissimilar devices? I presume "get a ~1% light meter and some consistent light sources, match up values against displayed reading, create formula" will be about the only way (though again, <~$100 light meters are a pain to get automated readings out of.. if anyone knows of a decent light meter that speaks serial/usb/ethernet/something for readings, I'd love to hear about it!)The only unusual requirement here is that the readings need to be collected via an automated test routine. I'm pretty flexible in how the data is collected; I currently run most of my tests via python scripts that connect to various instruments over RS232 over USB, SCPI-VXI over ethernet, and ADC's connected to Raspberry Pi's and Arduino's over ethernet. So adding another collection routine isn't a huge issue. (though bonus points for being accessible via ethernet from the get-go! I'm a ~20 year sysadmin on top of everything else I've done, distributed networking from PHY through to application layers has been second nature to me for ~15+ years, and being able to script and perform automated tests at clients homes or in industrial settings is always a good feature of any tool worth buying!)Only thing I'm not a fan of is Windows API specific testing / automaton; I like my cross-platform languages + interfaces. I can always translate applications or drivers if source is available but I tend to find "windows only" sensors or measurement devices rarely provide source code. (though, honestly, whatever.. Virtual Machines are cheap and easy to instance!)Thanks!