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Limiting current for a Adafruit DotStar 3444 LED Matrix
Moderators: adafruit_support_bill, adafruit

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Limiting current for a Adafruit DotStar 3444 LED Matrix

by labbinaer on Thu Jan 13, 2022 9:28 am

If set to 100% brightness, Adafruit DotStar 3444 LED Matrix can get extremely hot. I have a scenario where I cannot be 100% sure that this will never happen. Can you think of a way to limit the amps supplied to a DotStar, for example with an Current Limiter Circuit of with a (resettable) fuse? Limiting it by code via brightness is possible but may still be too unsafe if for example the communication glitches.

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Re: Limiting current for a Adafruit DotStar 3444 LED Matrix

by adafruit_support_bill on Thu Jan 13, 2022 12:32 pm

Software limits should be your primary means of limiting. It is possible to use an in-line self-resetting fuse as an emergency backup. The risk there is that the signal voltage will then exceed the supply voltage which exceeds the maximum voltage rating for the input signal. (See 3rd page of the data sheet):

https://cdn-learn.adafruit.com/assets/a ... MD_LED.pdf

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Re: Limiting current for a Adafruit DotStar 3444 LED Matrix

by labbinaer on Fri Jan 14, 2022 6:24 am

Very good point, thanks. Would the Pull-Up RIN 570 kO normally be used to compensate for this?

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Re: Limiting current for a Adafruit DotStar 3444 LED Matrix

by adafruit_support_bill on Fri Jan 14, 2022 6:59 am

A pullup would not help matters. You want the signal to go to zero as soon as the power is cut.

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Re: Limiting current for a Adafruit DotStar 3444 LED Matrix

by labbinaer on Fri Jan 14, 2022 2:52 pm

It think the fuse (PTC/RTS) could go in front of the microcontroller, so that everything gets cut off at the same time.

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Re: Limiting current for a Adafruit DotStar 3444 LED Matrix

by adafruit_support_bill on Fri Jan 14, 2022 2:55 pm

Yes. Cutting power to the whole system would work. You just want to avoid the case where you are still sending signals to the unpowered pixels.

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Re: Limiting current for a Adafruit DotStar 3444 LED Matrix

by labbinaer on Fri Jan 14, 2022 2:59 pm

Thanks a ton! I hope I remember posting my solution here as soon as I selected and tested the circuit!

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Please be positive and constructive with your questions and comments.