Author Topic: How can I drive this LED matrix?  (Read 412 times)

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Offline jammo

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How can I drive this LED matrix?
« on: August 08, 2018, 03:45:28 pm »
I've got a Maplin (RIP) LED matrix display. Unfortunately, the ROM chip has died on the controller board. But I have no reason to believe that the LEDs don't work.

Is there any way of controlling this matrix without the original controller board? Pictures below.

Matrix front

Matrix back
Controller front
Controller back
Matrix closeup
Thanks!
 

Offline Pirateguy

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Re: How can I drive this LED matrix?
« Reply #1 on: August 13, 2018, 01:18:49 am »
well those ICs on the front are the drivers, looks like all this needs is a microcontroller to tell it what to do,
check the numbers on those chips and google up their data sheets, and also do a google on the part number + arduino
(odds are somebody wrote a library or tutorial for it)
 

Offline Ian.M

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Re: How can I drive this LED matrix?
« Reply #2 on: August 13, 2018, 02:16:23 am »
Not quite - the column drivers + a 60 bit shift register to control them are on the display board, but the row drivers are on the controller.   If you want to drive the display board off something like an Arduino, you'll need seven power P-MOSFETs to replace them either low Vgs threshold ones if it runs the matrix from 5V or ordinary ones with gate drivers to handle the level shifting if it runs from a higher voltage.

What happened to the ROM?  If you don't need to add features the original didn't support, it might be easier to find someone who's got one and can copy it.   
 

Offline Eka

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Re: How can I drive this LED matrix?
« Reply #3 on: August 13, 2018, 03:03:11 am »
Not quite - the column drivers + a 60 bit shift register to control them are on the display board, but the row drivers are on the controller.   If you want to drive the display board off something like an Arduino, you'll need seven power P-MOSFETs to replace them either low Vgs threshold ones if it runs the matrix from 5V or ordinary ones with gate drivers to handle the level shifting if it runs from a higher voltage.

What happened to the ROM?  If you don't need to add features the original didn't support, it might be easier to find someone who's got one and can copy it.   
I second all of this.

The column drivers are the ones next to the resistors. The shift register are the other chips. Simple enough to drive. The chip that drives the rows is the STA402A on the driver board which leads me to: https://www.digikey.com/product-detail/en/sanken/STA402A/STA402A-ND/4289345 It is buffered from the MCU by U10 and U11?, whatever they are. The controller board may be designed to run two of the arrays, but this one may be paralleling the STA402A PNP Darlington driver chips to drive the one long array. I'd need to see the cables better.
 

Offline Ian.M

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Re: How can I drive this LED matrix?
« Reply #4 on: August 13, 2018, 04:01:06 am »
There's also likely to be an issue with the row multiplexing - if it stops, the continuous LED current is probably high enough to burn out LEDs that are on in the row that its stuck on.    This isn't a problem once you have 100% tested stable firmware, but during development unless you are very good and very lucky, to avoid letting the magic smoke out you either need to reduce the LED supply voltage to reduce the max continuous current through them, or patch in a circuit to monitor the duty cycles of the seven row drive lines and if any stay over 15% for long, disable the display.
 


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