Connecting RGB LEDs

FantomXR · June 2, 2013, 10:48pm

I’m trying to understand, what would be the easiest way to connect around 70 RGB LEDs (so around 210 single LEDs). I took a look into the NG-manual. In the DOUT-Matrix chapter it says:

“These parameters allow to drive duo-colour or RGB LEDs by using a second set of DOUTs connected to the green LEDs.”

and

“These parameters allow to drive RGB LEDs by using a third set of DOUTs connected to the blue LEDs.”

Do I really need to setup one DOUT (not shift register) per color? If didn’t make a mistake in my calculation, one DOUT would be enough to drive 70 RGB LEDs in matrix-mode. I thought, I could connect the LEDs like this:

LED1:

Red = D7

Green = D6

Blue = D5

LED2:
Red = D4

Green = D3
Blue = D2

etc.

Marxon · June 2, 2013, 11:32pm

Hi FantomXR

I’m trying to understand, what would be the easiest way to connect around 70 RGB LEDs (so around 210 single LEDs).

Here is one example:

http://discourse.midibox.org/t/topic/17288

Best regards

Marxon

Duggle · June 3, 2013, 1:42am

Marxon links to a long thread where issues are discovered and resolved, it has a happy ending!

A few points in summary:

64 RGB LEDs can be driven by a single DOUTx4 PCB
The (4) shift registers of the DOUT are organised:(1) row drivers, (1)Reds, (1)Greens, (1)Blues, assignable on a register, not on a bit level.
This 8x8 RGB LED matrix provides at least 64 colours and looks great.
I upgraded to a 16x4 matrix by adding 3 more shift registers (7 total), this gives higher duty cycle, more colours, even brighter.

FantomXR · June 3, 2013, 8:41am

Thanks!

I read thru the thread. Interesting stuff out there!

I want to use ULN2803 drivers anyway to drive the LEDs. I hope, I don’t need to setup a 16x4 instead of 8x8 to get good brightness levels.

I think I need to hook up some kind of schematic to not get confused by all the connections

Anyway: If I want to use more than 64 RGB LEDs it’s necessary to use a second DOUTx4 or it’s possible to enhance it to a 10x8 matrix?

Duggle · June 3, 2013, 12:22pm

The ULN drivers are good to use, but they have a ~=1V minimum output so you can compensate by using a lower series resistor (I used 82 R).

You could set up a second DOUT matrix to provide up to another 64 LEDs.

The 8x8 matrix I built was quite bright. I made rectangular diffusers out of opal perpex which spread (and de-intensified) the light.

I constructed the matrix in a modular fashion:

4 LEDs to a strip of matrix board with cathodes commoned together along the horizontal (a “module”)
2 modules for each row of 8 leds (a link connecting the common cathodes)
8 rows in total.
the RGB anodes of each LED have 3 pin header pointing in one direction, and 3 wires 10cm long, with a 3 header socket wired to it.
columns are formed by chaining tegether the header plug/sockets
The output of the ULN pins wired to each row.

If you draw diagram it helps to make things clear.

FantomXR · June 4, 2013, 12:52pm

Yes!
I draw a diagram in Eagle to make it clear.

Because I need to use a second DOUT anyway, the first matrix will be 6x8 (six RGB LEDs in eight rows). Did I get it right, that the first SR sets the rows. On the second SR I need to connect all red LEDs (which would be six lines, each with 8 LEDs), third SR all green, 4th SR all blue.

Cause your schematic in this topic

http://discourse.midibox.org/t/topic/17288

says something else.

Duggle · June 4, 2013, 9:44pm

http://discourse.midibox.org/t/topic/17288

Yes, the situation evolved during the thread.

Did I get it right, that the first SR sets the rows. On the second SR I need to connect all red LEDs (which would be six lines, each with 8 LEDs), third SR all green, 4th SR all blue.

Correct, and the nice thing is, the configuration variables: sr_dout_sel1, sr_dout_r1, sr_dout_g1, sr_dout_b1 can be assigned to any SR in the DOUT chain.

As you may have recognised, 8 rows of 6 has a little less wiring than 6 rows of 8 (8+3*6=26 Vs. 6+3*8=30), though how you plan on routing the wiring, layout etc, can influence which wiring scheme is best for you (they’re functionally the same).

Note that the second DOUT matrix will have it’s own sr_dout_sel1, sr_dout_r1, sr_dout_g1, sr_dout_b1 assignments.

FantomXR · June 4, 2013, 10:08pm

Great!

I drawed a schematic. But I think I need to sit right in front of the LEDs to know, where which wire to solder But all orders were done today. I should get a few nice packages the next days.

I forgot to mention: I have some PCBs with a led ring on it. Its 0603 warmwhite SMD LEDs. How to connect them to the two DOUTs? Is that possible or do I need a dedicated DOUT for those LEDs? If I connect them all to one color-SR there shouldn’t be a problem, right?

Duggle · June 4, 2013, 10:48pm

I forgot to mention: I have some PCBs with a led ring on it. Its 0603 warmwhite SMD LEDs. How to connect them to the two DOUTs? Is that possible or do I need a dedicated DOUT for those LEDs? If I connect them all to one color-SR there shouldn’t be a problem, right?

Not quite sure exactly what you mean here.

If you nave extra LED’s you want to drive then yes, you could connect them to the spare columns of the RGB matrix.

To have proper control over the LEDs you’d only connect LEDs to the red columns. I don’t know how or if LED rings could be driven this way.

Simpler and probably a lot better to add SR’s for extra LED rings.

FantomXR · June 14, 2013, 9:24am

Thanks for your help!

Another one: How to connect an expression pedal to the LPC? It has a stereo jack, so I assume, I need to connect GND to GND, tip and ring to a separate analog-in on the LPC. But how to assign them in the NGC so it behaves like one controller?

Duggle · June 14, 2013, 9:01pm

Thanks for your help!

Another one: How to connect an expression pedal to the LPC? It has a stereo jack, so I assume, I need to connect GND to GND, tip and ring to a separate analog-in on the LPC. But how to assign them in the NGC so it behaves like one controller?

I’d assume the expression pedal is a potentiometer.

The wiper will change it’s resistance to ground. Tip or ring? Find out with meter.

The 3rd terminal will have constant resistance to ground. This is wired to 3.3V supply rail.

The wiper goes to the ADC input of Core.

Configure using EVENT_AIN.

FantomXR · June 15, 2013, 12:16am

Thanks!
I will try that… hopefully tomorrow morning

//edit: Moved it to MB_KB Thread. I forgot that my keyboard is running on MB_KB and not MB_NG.

FantomXR · July 2, 2013, 8:56pm

Okay, here we go!

I now connected 4 rows with 16 LEDs per row to D0:D3 of SR1. For now I just connected eight (8x4) of the green LEDs to D7:D0 of SR2 to see, if it’s working.

I connected the DOUT with the core. The first SR has no resistors, just bridges. SR 2-4 are equiped with ULN2803. I put a 82Ohm resistor to each output (so, 8 resistors).

I tried this code:

In this demo we configure individual brightness levels for the LEDs

RESET_HW

LCD “%C@(1:1:1)RGB Demo #1”

In the SR configuration we assume that the DOUTs are directly connected to J8/9 of the core

they emulate led functions

DOUT_MATRIX n=1 rows=4 inverted=0 sr_dout_sel1=1 sr_dout_r1=2 sr_dout_g1=3 led_emu_id_offset=1001

note: actually the sr_dout_sel1 in DOUT_MATRIX could be removed,

since DIN_MATRIX already outputs the selection pulses there

this is just for the case that somebody copy&pastes the definition…

LED Functions (assigned to the same events like the buttons)

EVENT_LED     id=1001 type=NoteOn key=36 chn=1 rgb=15:0:0
EVENT_LED     id=1002 type=NoteOn key=37 chn=1 rgb=15:0:0
EVENT_LED     id=1003 type=NoteOn key=38 chn=1 rgb=15:0:0
EVENT_LED     id=1004 type=NoteOn key=39 chn=1 rgb=15:0:0
EVENT_LED     id=1005 type=NoteOn key=40 chn=1 rgb=15:0:0
EVENT_LED     id=1006 type=NoteOn key=41 chn=1 rgb=15:0:0
EVENT_LED     id=1007 type=NoteOn key=42 chn=1 rgb=15:0:0
EVENT_LED     id=1008 type=NoteOn key=43 chn=1 rgb=15:0:0

EVENT_LED     id=1033 type=NoteOn key=44 chn=1 rgb=0:15:0
EVENT_LED     id=1034 type=NoteOn key=45 chn=1 rgb=0:15:0
EVENT_LED     id=1035 type=NoteOn key=46 chn=1 rgb=0:15:0
EVENT_LED     id=1036 type=NoteOn key=47 chn=1 rgb=0:15:0
EVENT_LED     id=1037 type=NoteOn key=48 chn=1 rgb=0:15:0
EVENT_LED     id=1038 type=NoteOn key=49 chn=1 rgb=0:15:0
EVENT_LED     id=1039 type=NoteOn key=50 chn=1 rgb=0:15:0
EVENT_LED     id=1040 type=NoteOn key=51 chn=1 rgb=0:15:0

EVENT_LED     id=1009 type=NoteOn key=52 chn=1 rgb=15:15:0
EVENT_LED     id=1010 type=NoteOn key=53 chn=1 rgb=15:15:0
EVENT_LED     id=1011 type=NoteOn key=54 chn=1 rgb=15:15:0
EVENT_LED     id=1012 type=NoteOn key=55 chn=1 rgb=15:15:0
EVENT_LED     id=1013 type=NoteOn key=56 chn=1 rgb=15:15:0
EVENT_LED     id=1014 type=NoteOn key=57 chn=1 rgb=15:15:0
EVENT_LED     id=1015 type=NoteOn key=58 chn=1 rgb=15:15:0
EVENT_LED     id=1016 type=NoteOn key=59 chn=1 rgb=15:15:0

EVENT_LED     id=1041 type=NoteOn key=60 chn=1 rgb=4:15:0
EVENT_LED     id=1042 type=NoteOn key=61 chn=1 rgb=4:15:0
EVENT_LED     id=1043 type=NoteOn key=62 chn=1 rgb=4:15:0
EVENT_LED     id=1044 type=NoteOn key=63 chn=1 rgb=4:15:0
EVENT_LED     id=1045 type=NoteOn key=64 chn=1 rgb=4:15:0
EVENT_LED     id=1046 type=NoteOn key=65 chn=1 rgb=4:15:0
EVENT_LED     id=1047 type=NoteOn key=66 chn=1 rgb=4:15:0
EVENT_LED     id=1048 type=NoteOn key=67 chn=1 rgb=4:15:0

EVENT_LED     id=1017 type=NoteOn key=68 chn=1 rgb=15:4:0
EVENT_LED     id=1018 type=NoteOn key=69 chn=1 rgb=15:4:0
EVENT_LED     id=1019 type=NoteOn key=70 chn=1 rgb=15:4:0
EVENT_LED     id=1020 type=NoteOn key=71 chn=1 rgb=15:4:0
EVENT_LED     id=1021 type=NoteOn key=72 chn=1 rgb=15:4:0
EVENT_LED     id=1022 type=NoteOn key=73 chn=1 rgb=15:4:0
EVENT_LED     id=1023 type=NoteOn key=74 chn=1 rgb=15:4:0
EVENT_LED     id=1024 type=NoteOn key=75 chn=1 rgb=15:4:0

EVENT_LED     id=1049 type=NoteOn key=76 chn=1 rgb=8:15:0
EVENT_LED     id=1050 type=NoteOn key=77 chn=1 rgb=8:15:0
EVENT_LED     id=1051 type=NoteOn key=78 chn=1 rgb=8:15:0
EVENT_LED     id=1052 type=NoteOn key=79 chn=1 rgb=8:15:0
EVENT_LED     id=1053 type=NoteOn key=80 chn=1 rgb=8:15:0
EVENT_LED     id=1054 type=NoteOn key=81 chn=1 rgb=8:15:0
EVENT_LED     id=1055 type=NoteOn key=82 chn=1 rgb=8:15:0
EVENT_LED     id=1056 type=NoteOn key=83 chn=1 rgb=8:15:0

EVENT_LED     id=1025 type=NoteOn key=84 chn=1 rgb=15:8:0
EVENT_LED     id=1026 type=NoteOn key=85 chn=1 rgb=15:8:0
EVENT_LED     id=1027 type=NoteOn key=86 chn=1 rgb=15:8:0
EVENT_LED     id=1028 type=NoteOn key=87 chn=1 rgb=15:8:0
EVENT_LED     id=1029 type=NoteOn key=88 chn=1 rgb=15:8:0
EVENT_LED     id=1030 type=NoteOn key=89 chn=1 rgb=15:8:0
EVENT_LED     id=1031 type=NoteOn key=90 chn=1 rgb=15:8:0
EVENT_LED     id=1032 type=NoteOn key=91 chn=1 rgb=15:8:0

EVENT_LED     id=1057 type=NoteOn key=92 chn=1 rgb=15:12:0
EVENT_LED     id=1058 type=NoteOn key=93 chn=1 rgb=15:12:0
EVENT_LED     id=1059 type=NoteOn key=94 chn=1 rgb=15:12:0
EVENT_LED     id=1060 type=NoteOn key=95 chn=1 rgb=15:12:0
EVENT_LED     id=1061 type=NoteOn key=96 chn=1 rgb=15:12:0
EVENT_LED     id=1062 type=NoteOn key=97 chn=1 rgb=15:12:0
EVENT_LED     id=1063 type=NoteOn key=98 chn=1 rgb=15:12:0
EVENT_LED     id=1064 type=NoteOn key=99 chn=1 rgb=15:12:0

But… no lights… nothing happens…

any suggestions?

Duggle · July 2, 2013, 10:53pm

I connected the DOUT with the core. The first SR has no resistors, just bridges. SR 2-4 are equiped with ULN2803. I put a 82Ohm resistor to each output (so, 8 resistors).

You’re using common cathode RGB LED’s right?

If so, you cant use ULN2803 as drivers on SR2..4 because ULN2803 is a “low side driver” (Darlington NPN) and won’t work as a high side driver.

If your LEDs are common cathode, move one of the ULN’s onto SR1, remove the others and replace with a resistor (SR2..4). Also change to “inverted=1”.

This configuration works geat.

FantomXR · July 2, 2013, 11:07pm

Thanks for this hint!

I will check this out tomorrow and give you a status update.

Should I take 82Ohm or standard 220Ohm resistors?

But the code should work you say?

Duggle · July 2, 2013, 11:24pm

Here’s an excerpt from my config:

#rgbled
DOUT_MATRIX n=1 rows=4 inverted=1 sr_dout_sel1=1 sr_dout_r1=2 sr_dout_r2=5 sr_dout_g1=3 sr_dout_g2=6 sr_dout_b1=4 sr_dout_b2=7 led_emu_id_offset=1001

# LEDs go to colours according to bank selection
EVENT_LED value=127 id=1001 bank=1 rgb=15:0:0
EVENT_LED value=127 id=1002 bank=1 rgb=15:0:0
EVENT_LED value=127 id=1003 bank=1 rgb=15:5:0


EVENT_LED value=127 id=1001 bank=2 rgb=0:0:15
EVENT_LED value=127 id=1002 bank=2 rgb=0:0:15
EVENT_LED value=127 id=1003 bank=2 rgb=7:0:15 

EVENT_LED value=127 id=1001 bank=3 rgb=7:15:0
EVENT_LED value=127 id=1002 bank=3 rgb=7:15:0
EVENT_LED value=127 id=1003 bank=3 rgb=15:7:0

The way you have your config is to light the LED’s only when the note is active.

FantomXR · July 2, 2013, 11:35pm

Thank you so much!

I will keep you updated!

Duggle · July 3, 2013, 1:42am

Should I take 82Ohm or standard 220Ohm resistors?

When I changed my array from 8x8 to 4x16, I added a DOUT PCB that already had 220R fitted (The first DOUT had 82R fitted). So half is 82R the other half is 220R and it is not at all clear that one half is brighter…

I think this is because the current limiting is mainly in the SR’s.

Conclusion: it probably doesn’t matter. It may be a good idea to test the brightness on one or two LEDs before you solder a whole bunch of resistors anyhow…

You may want the whole array dimmer for some reason.

Also it may be good to check that R,G and B are fairly balanced with the same value resistor. In my case they were, but…

FantomXR · July 3, 2013, 10:49am

Works perfect!! Thank you!

Is it possible to set up an encoder to scroll / fade through all the different possible colors?

FantomXR · July 3, 2013, 7:40pm

And another question:

I now connected all red and green LEDs.

I have a problem: I can’t swich the LEDs off. I tried rgb=x:x:x to 0:0:0 and also tried to set the value to 0. The LED are still on… they are low, but they are on…