Author Topic: Current limiting circuit?  (Read 1832 times)

0 Members and 1 Guest are viewing this topic.

Offline mbestTopic starter

  • Contributor
  • Posts: 19
  • Country: ca
Current limiting circuit?
« on: February 22, 2019, 05:00:45 pm »
I have these 18650 battery shields, that use a FP6298 http://www.feeling-tech.com.tw/km-master/ezcatfiles/cust/img/img/24/fp6298v063.pdf for 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 as https://www.electronics-notes.com/articles/analogue_circuits/power-supply-electronics/current-limiter-circuit.php, polyfuse?
 

Offline Nusa

  • Super Contributor
  • ***
  • Posts: 2418
  • Country: us
Re: Current limiting circuit?
« Reply #1 on: February 22, 2019, 05:43:36 pm »
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.
 

Offline mbestTopic starter

  • Contributor
  • Posts: 19
  • Country: ca
Re: Current limiting circuit?
« Reply #2 on: February 22, 2019, 07:39:48 pm »
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.
 

Offline lordvader88

  • Frequent Contributor
  • **
  • !
  • Posts: 935
  • Country: ca
Re: Current limiting circuit?
« Reply #3 on: February 22, 2019, 11:52:06 pm »
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.
 

Offline jackthomson41

  • Regular Contributor
  • *
  • Posts: 53
  • Country: us
Re: Current limiting circuit?
« Reply #4 on: February 23, 2019, 12:06:45 pm »
You can place a resistor but I think that won't reduce the current drawn from the battery. I think the best way to control Arduino LED current 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.
« Last Edit: April 18, 2020, 11:29:19 pm by jackthomson41 »
 

Offline Nusa

  • Super Contributor
  • ***
  • Posts: 2418
  • Country: us
Re: Current limiting circuit?
« Reply #5 on: February 23, 2019, 03:04:47 pm »
You can place a resistor but I think that won't reduce the current drawn from the battery. I think the best way to control LED current 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.

That 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.
 

Offline jackthomson41

  • Regular Contributor
  • *
  • Posts: 53
  • Country: us
Re: Current limiting circuit?
« Reply #6 on: February 24, 2019, 05:18:14 pm »
That 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.

Yeah I just search it out WS2813, I thought he was using simple LED with microcontroller, my bad.
« Last Edit: April 18, 2020, 11:31:23 pm by jackthomson41 »
 

Offline mbestTopic starter

  • Contributor
  • Posts: 19
  • Country: ca
Re: Current limiting circuit?
« Reply #7 on: February 27, 2019, 08:50:04 pm »
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.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf