levon Posted January 20, 2010 Report Share Posted January 20, 2010 (edited) Ok, no replies, lets try again..... Darlington array's or not? the original BLM doesnt require these, but the protodeck uses ULN28003 darlington array's and BC547 NPN transistor's. i have seen posts where people say you can not provide enough power with out these, but the BLM seems to work with out it. anyone have any input? Original post: Im working on a LED matrix, just standard Red LED's designed in Eagle CAD to go under my Nintendo DS touch screen (when i get it working ) Im using a PIC18f452, custom coding my MIOS app. DOUTx4 board for the LED's and i would rather use an LED matrix than 2 DOUTx4 boards. Have a few questions. 1) the Protodeck uses ULN28003 darlington array's and BC547 NPN transistor's, but the MB 6582 SID doesnt use them for the LED matrix. Are these required? 2) I was thinking of having 2 LED matrices one which is 8x8 red LED's, and another that is 2x8 LED's. is it possible to treat this as one 10x8 matrix? 3) anyone with experience in PCBs, is my design ok? the LED's are on one side, and the resistors are on the bottom. 4) the DIL's pinning for the LED's are not what the BLM code expects, is it easier to change this in the code to the correct order? or by the wires going from this board, to the DOUT board? cheers, Edited February 9, 2010 by levon Quote Link to comment Share on other sites More sharing options...
levon Posted February 19, 2010 Author Report Share Posted February 19, 2010 bump... anyone have some more info, im lost at the moment. Quote Link to comment Share on other sites More sharing options...
Wilba Posted February 19, 2010 Report Share Posted February 19, 2010 The MB-6582 does use BC547 for sinking both common cathodes of LED "columns" (up to 16!) and also the switch in the switch matrix. I just posted why here: They aren't always required, it all depends on how many LEDs you want to use, their brightness at low current levels, how much current will be sinked by one DOUT pin, etc. You can get away with no transistors (re sammichSID) or play it safe and put them in. I used BC547 instead of Darlingtons because the collector emitter voltage of Darlingtons would be too high for use in a switch matrix, i.e. the voltage at the DIN input if I used Darlingtons would be close to or maybe over the logic low voltage threshold, depending on current sinked through the Darlington. Quote Link to comment Share on other sites More sharing options...
protofuse Posted February 21, 2010 Report Share Posted February 21, 2010 (edited) about the design, you could check my protodeck's page. this one could help too: Edited February 21, 2010 by protofuse Quote Link to comment Share on other sites More sharing options...
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