midio128 strange problem

[maxx11]

I am building a band organ with a core and 2 DOUT modules feeding relays thru uln2803a's. The midi in is fed from a palm vx running ittymidi software. When first tested with a song not all notes played.I have a midi file where you can play each note separately and found 10 midi channels not firing(out of 64). I disconnected everything and hung LED's on the DOUT outputs. When I send a midi note signal from the player,the respective LED lights for each channel, so this should be telling me that everything is working correctly? I have a LCD connected to the core and when I send a note (say C) the LCD shows note C. So I hook everything back up and send single note commands to the organ relays as I did with the LED's,only again I have 10 or 12 channels not firing,some the same as not firing previously, some different. I hook the LED's back up to the channels that are not firing and they light right up. Any suggestions? I am totally confused. One other issue is that the LED's sometimes don't turn off when I hit stop but I think that my player is not always sending a note off command. Appreciate any help you can give me. Thanks.

[lylehaze]

I can offer a suggestion or two..

You mentioned that you have 10 or 12 channels not firing out of 64. I think you probably mean 10 or 12 notes, as regular MIDI only supports a maximum of 16 channels per port.

I know it sounds like a unimportant detail, but details count when trying to describe a problem to others.

Based on your comments, the DOUT modules seem to be working.. can you draw a diagram showing how your ULN's, relays, DOUT connections, and power supply all connect together?

even if you just detail a single note or two, that might give clues we need.. and do you have the tech details for the relays? like how much current they draw, and whether the load they are switching is powered from the same supply?

Basic troubleshooting ideas: I think the regular DOUT module has outputs in groups of 8.. so can you take a single group of 8 relays and plug them in one at a time to each of the DOUT connectors? Will the relays work fine when they aren't loaded, but work less reliably when they are switching loads? What is powering the whole thing? You're not using the core regulator to supply power to the relays are you? Which core are you using?

Good luck with your troubleshooting!

LyleHaze

[maxx11]

More info: core 8 with 18F452 PIC,ULN's mounted on DOUT board, relays and core powered separately from a 12 volt motorcycle battery, relays are 90 ohm 133ma at 12 volts,each relay has a flyback diode and series diode to isolate 2 ranks. Tried a couple of things: moved the outputs of DOUT group 3 01,02,04 05 that didn't work to group 4 01,02,04 05 and sent each a midi signal separately and they worked, tried again and they didn't work. Some,but not all, of the outputs feed 2 relays each with a separate +12 common buss. For now these are tied together, I will see what happens if I remove one, but since some of the outputs that don't work only feed 1 relay I can't see that it would make a difference. Thanks for your help.

[lylehaze]

Thanks for posting more info.. more is usually better. :)

If I were a betting man, I'd guess your grounds are not all connected

It looks like pins 9 and 10 of each ULN need to be manually connected to GND and the positive power supply for your relays.

Since the LED tests you have tried seem to pass, I think you may have a power supply connection issue. Note that the ground

from the relay power supply(supplies?) MUST be firmly connected to PIN 9 of all ULNs AND to the core ground as well.

Pin 10 of each ULN should be connected to the relay positive supply, NOT to the 5 volt core supply.

Good Luck!

LyleHaze

[maxx11]

Thanks Lyle, was going to try this today but got more confused, using a DOUT board from smashtv but don't see any connections for pins 9 and 10 of the uln which is mounted on the board. There is a Vs pin on the J3-6 output connectors but I read .7 volts between this pin and power supply ground. Is it ok to tie the Vs pins from J3-6 to supply ground? Thanks for your help!

[lylehaze]

Thanks Lyle, was going to try this today but got more confused, using a DOUT board from smashtv but don't see any connections for pins 9 and 10 of the uln which is mounted on the board. There is a Vs pin on the J3-6 output connectors but I read .7 volts between this pin and power supply ground. Is it ok to tie the Vs pins from J3-6 to supply ground? Thanks for your help!

I believe we found 2 problems in one statement.. But first, a word from our lawyers:

I do not have a DOUT board in front of me, so I cannot test ANYTHING.

I do not work for SmashTV, nor can I speak for him.

I do not have a ULN2803 chip in front of me, just a datasheet (which you should have in front of you, as well)

I am not responsible for anything I say in this forum.. In the end it's all up to you and all your fault. :)

If anything I suggest results in a thermonuclear explosion, we never met.

With all that said, I am a competent technician, programmer, and circuit board designer, so you can probably believe what I'm telling you, or at least try to verify it by reading the datasheet yourself.

To start, you'll need to see a datasheet for a ULN2803a chip. Use google for this, and open it in another tab so you can switch back and forth from this discussion.

Now if you look at the _LOGICAL_ diagram, it looks like each output is just the opposite (or inversion) of each input.. If you put in a HIGH signal, you'll get a LOW signal out.

That is indicated by each buffer (triangle) having a little circle(inverter) on the output. There are also a couple diodes on each output, we'll get back to those later.

Now, on to the schematic diagram of a single channel:

Please notice that except for one of the diodes on output, there is no positive connection here. the input signal is referenced to ground, and the output is "sunk" to ground(NPN transistor there) when the output should be low. This is often called an "open collector" output. (google that if you care)

Back to our reality:

Since the signal that drives the input is coming from a chip on the DOUT board, the ULN Gnd and the Vs from the DOUT must be connected.

Since the whole purpose of this chip is to provide a high current switch to GND, the ULN Gnd and the relay power supply Ground MUST be connected.

So yes, based on this, You must connect the DOUT Vs, the 12 volt relay power supply GND, and ALL the ULN pin 9s together.

While you're there, you should also connect all the ULN pin 10s to the relay power + line, for those output protection diodes.

Does this mean there's a flaw in Smash's board design? I think the board was designed for resistors there, and the "extra" holes at pins 9 and 10

were to ALLOW a ULN to be inserted, but it's up to you to connect them as you need. That's what it looks like, anyway.

BUT don't take my word for it! Study up, read the datasheet, google anything you're not sure of, or even invite Smash to read what we have talked about here.

He's a real busy guy, but anything is possible. :)

Or just try it, the worst you could do is blow up the Kitchen.

Good Luck, and please report back with your findings!

LyleHaze

P.S. Practice safe science, use a fuse.

Edited December 30, 2010 by lylehaze

[smashtv]

Hi guys,

LyleHaze has it right, you will have to add wires/jumpers to pin 9 and 10 yourself.

My reasoning for what looks like some incomplete trace tetris:

My DOUT R3 layout was set up for ULN2803 driver chips only, with the ground plane connected to the ULN chip etc. It works/worked great, but required a lot of effort with a knife to disconnect the plane from the pin when using a UDN or other alternate driver IC.

With some feedback from the pipe organ guys I left those pins open from R4 on, to support other driver chips and to allow for isolation between control and drive power rails if needed. R4 and R5 can be built for source or sink drivers without major surgery on the copper layer. :)

Have fun and let me know if I caused more questions!

Best regards

Tim

[maxx11]

Thanks Tim for the clarification on the DOUT board. Wellll I connected the ULNs to ground and +12 common ( pins 9 & 10 ) and DOUT Vs to ground. All pipes play BUT there are always 2 that don't,always different ones. At first group 7 D4 and D7 were dead. Tested with LED's and reconnected and they worked,but then group 6 D6 and D7 were dead. Checked with LED's, reconnected and they worked but 2 others were out. Maybe it's a software bug and I need to reload? Occasionally a note will not turn off when hitting stop. A pause command will usually do it. Don't know if it is midio or my player. Will have to hook up my LCD to the core and see if I can see anything. Any suggestions? Thanks!

Edited December 31, 2010 by maxx11