LED Matrix - 12V

A "new fashioned" televisor, using an Arduino to drive the motor and display.

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Re: LED Matrix - 12V

Postby Steve Anderson » Thu Jul 06, 2017 2:25 pm

Andrew Davie wrote:...Arduino however was at 97C running at 17v in. Gotta fix that!

Yep. It may be rated to that temperature but that's the surface temperature you're measuring, the actual chip inside will be quite a few degrees hotter, 10s of degrees. Not a good omen for reliability.

Steve A.
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Re: LED Matrix - 12V

Postby Andrew Davie » Thu Jul 06, 2017 2:39 pm

Steve Anderson wrote:
Andrew Davie wrote:...Arduino however was at 97C running at 17v in. Gotta fix that!

Yep. It may be rated to that temperature but that's the surface temperature you're measuring, the actual chip inside will be quite a few degrees hotter, 10s of degrees. Not a good omen for reliability.

Steve A.


The microcontroller ATMEGA32U4 on-board is only rated to 85C so I was already pushing it!
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Re: LED Matrix - 12V

Postby Steve Anderson » Thu Jul 06, 2017 2:42 pm

I would guess that what is actually 97C is the on-board regulator not so much the processor. You gotta get rid of that 17V, hence my suggestion of an 8V supply.

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Re: LED Matrix - 12V

Postby Andrew Davie » Thu Jul 06, 2017 3:02 pm

Steve Anderson wrote:I would guess that what is actually 97C is the on-board regulator not so much the processor. You gotta get rid of that 17V, hence my suggestion of an 8V supply.

Steve A.


Yep. Currently thinking input 14-23VDC, then a chain of regulators. 1) input --> 12VDC (for motor, LED), then 2) 12VDC --> 8VDC for Arduino, then 3) 8VDC --> 5VDC for amplifier. Alternatively, just use the aforementioned LM2596-based adjustable regulators and have all connected to the main input, with all generating exactly the required voltage independently (rather than daisy-chained).
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Re: LED Matrix - 12V

Postby Steve Anderson » Thu Jul 06, 2017 6:51 pm

I suggested the 8V regulator be fed directly from the 'power brick' as the combined start-up currents of the motor and all else my cause the most upstream regulator to also shut down. They're only rated for 1A/1.5A. There is the possibility that you may also exceed the dissipation limits of these regulators as you haven't allowed for any heatsinks. They (at a quick glance) seem to be positioned close to each other, this will not help with temperature control.

I suggest you DO NOT daisy chain the regulators, you may need some heatsinks, but that's the price you pay for linear regulators. I avoid switched-mode regulators unless there is no other choice. I assume you'll be needing a case for this device, if made of metal - one instant heatsink.

Silicon hates heat. Germanium even more! But you don't have to worry about Germanium here.

One suggestion I did in the past below.

Steve A.
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Re: LED Matrix - 12V

Postby Andrew Davie » Mon Oct 30, 2017 10:45 pm

I find it hard to pass up these...

https://www.aliexpress.com/item/Car-led ... 30678.html

Car-led-super-White-cob-led-12v-48-SMD-car-styling-Reading-indoor-Lamp-led-Car.jpg
Car-led-super-White-cob-led-12v-48-SMD-car-styling-Reading-indoor-Lamp-led-Car.jpg (165.43 KiB) Viewed 1747 times


... at just US$0.65 each, inclusive of shipping! I hope they will be suitable as a drop-in replacement for my existing LED arrary. Perhaps not quite as bright, but that would be OK. Will report back in 6 weeks or so when they arrive :) Amazing how they actually make money on these things.
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