Need ideas for a current monitoring with an windows / range of detection - Page 1
Forum section: electronics / projects

author: coromonadalix
author_rank: Super Contributor
timestamp: March 09, 2020, 02:29:44 pm
content: Hi @llI need ideas for designing a simple current monitoring circuit, i'm using 2x pelletier cooling devices at 12vdc, they normally sink 7 amps when they start working, sometimes with a peak / surge of 7.5 amps, and they get down at 6.3 / 6.5 amps after a while.They are controlled with 5 settings, the lowest (1st setting) is a 12vdc pulse at every 4 seconds, the second at 3 secs, third at 2 secs, fourth at 1 sec intervals, and the last setting is always powered on.On some occasions the pelletier wires break, or the pelletier cells are badly working ... i need to get a warning signal by light or a buzzer soundMy need would be : a 6 to 8 amps window monitoring and to check in a 5 sec window if there any current consumption present.This project is for a friend homemade laser show / projector, i dont have any schematic of the circuit, nor firmwares, nor source code of the control board, its an dmx512 chineesium thing, stc brand processor with an protected content, could not read it with an stc interface.The laser head cost a few $$$ when it die due to overheat. Its not an commercial project, its an hobby one.

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: March 09, 2020, 03:23:46 pm
content: if you just want to monitor that there's actually some current flowing you can use a reed contact inserted into a cylindrical air coil with 10-15 turns of wire. use the winding as "current sensor" with the number of turns to your likings and the reed contact to switch the buzzer/LED/GPIO.here is a picture of an ancient commercially available part (sorry, no part number, all imprint is gonsky).Edit: youdoknow that low-frequency pulsing of peltiers will shorten their lifetime due to mechanical fatigue caused by heat cycling?

author: coromonadalix
author_rank: Super Contributor
timestamp: March 09, 2020, 05:43:15 pm
content: oh never tought of that, but i need to check a time frame of 5 seconds and alert me if no current passed through ...I saw an arduino project with an INA226 ic, it seems to have an alert pin ??https://github.com/jarzebski/Arduino-INA226

author: jbb
author_rank: Super Contributor
timestamp: March 09, 2020, 09:25:47 pm
content: It seems like you’re trying to solve a slightly different problem.Is this a fair description?1 - the Peltier module keeps a laser diode at a constant temperature2 - the Peltier is driven by pulses of 12V DC3 - the Peltier breaks moderately often (which you would like to detect)4 - if you don’t catch it in time, the laser diode overheats and diesIs there a temperature sensor next to the laser diode?How often has the Peltier broken?If so, how about the following:1 - implement your proposed missing current detection (details to be determined)2 - fit an over temperature sensor next to the laser (because I think this is what you’re really concerned about)3 - reduce the failure rate of the Peltier. Right now, that pulsed drive circuit is causing a lot of mechanical fatigue due to temperature cycling. Peltier decides apparently like constant smooth driving, so maybe you could replace the built in temperature controller’s nasty pulse output with a smooth DC current output (this could maybe be done with an LED driver)