Current limiting circuit? - Page 1
Forum section: electronics / beginners

author: mbest
author_rank: Contributor
timestamp: February 22, 2019, 05:00:45 pm
content: I have these 18650 battery shields, that use a FP6298http://www.feeling-tech.com.tw/km-master/ezcatfiles/cust/img/img/24/fp6298v063.pdffor voltage regulation/current protection. Running 300 WS2813 (CS8208) LEDs that can go up to 6A, if I get the brightness limiting wrong in my microcontroller, the overcurrent protection trips. And then the only way to reset it is to pull the battery. Is there a good current limiting circuit I could build to stop the LEDs drawing more than say 4A, bonus points if it resets itself?Transistor current limited circuit such ashttps://www.electronics-notes.com/articles/analogue_circuits/power-supply-electronics/current-limiter-circuit.php, polyfuse?

author: Nusa
author_rank: Super Contributor
timestamp: February 22, 2019, 05:43:36 pm
content: I'd say either get your software right, or get a shield that will allow the power required by 300 LEDs at full brightness.But to answer the question, you've already got a current limiter on the board you've got. It's adjustable as described in the PDF you linked by changing a resistor. You should be able to make trigger at the 4A value you require with a little trial and error.

author: mbest
author_rank: Contributor
timestamp: February 22, 2019, 07:39:48 pm
content: The pain is that if the current limit is reached by the board it shuts down, and the only way to reset it is to pull the battery out, just trying to think of there is a way to make it more bulletproof, not so much to circuit damage, but easier to use if I make a mistake.I think I'll just have to limit the brightness to 40%/2.4A anyways since I need to conserve battery power.

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 22, 2019, 11:52:06 pm
content: What about using a reference voltage, a current sense resistor, a comparator, controlling a relay that could be on a timer ? Soon I'll try something similar with an SCR added, to shutdown a PSU in over-voltage situations.

author: jackthomson41
author_rank: Regular Contributor
timestamp: February 23, 2019, 12:06:45 pm
content: You can place aresistorbut I think that won't reduce the current drawn from the battery. I think the best way to controlArduino LEDcurrent here, is by PWM.Let's say your LED is turned ON on 5V and its drawing 500mA, now if you lower its voltage to 3V then the current drawn will also reduce.

author: Nusa
author_rank: Super Contributor
timestamp: February 23, 2019, 03:04:47 pm
content: Quote from: jackthomson41 on February 23, 2019, 12:06:45 pmThat would work if he were using raw LED's, but what he's using are addressable LED modules. Each LED has it's own tiny processor and the ability to receive commands and set the LED brightness. If you tried to PWM the power in this case, odds are you'd end up with something that won't work at all.

author: jackthomson41
author_rank: Regular Contributor
timestamp: February 24, 2019, 05:18:14 pm
content: Quote from: Nusa on February 23, 2019, 03:04:47 pmYeah I just search it out WS2813, I thought he was using simple LED withmicrocontroller, my bad.

author: mbest
author_rank: Contributor
timestamp: February 27, 2019, 08:50:04 pm
content: The other thing I'm thinking of doing, since only the USB power is controlled by the power switch, is use a USB connector to draw the power, or desolder one side of the battery holder and put a switch on it.