AMB Laboratories DIY Audio

[Nebby]

fixed

What was the root cause of the issue and how did you fix it? These things are useful for future readers that may find this post and have a similar issue.

Ah, nvm.

[Boinger]

Sorry I meant the links were fixed

Was just showing pics.

[linux-works]

lets try this.

on the 3 pin power select jumper (you have a white jumper near the 6pin i2c/power connector on the d1 controller) - see if you can remove that and run a resistor cutoff lead across all 3 wires and just remove the shunt since its not needed after this. the idea is to use both vcc wires that come from the lcduino 6pin i2c header. also check to make sure that the lcduino has both power pins (pin1, square solder pad, and the next one to it) are shorted/connected. I think they should be. the mod I want you to do on the d1 controller (and the other 3, too) will just use the extra wire in that bundle to help carry 5v. the 3 way jumper was meant to select 'which' of the 2 wires you run relay power from. in our case, there is not a separate relay power and 5v logic power; both are from the same place.

the wires you are using do look thick enough but having the 2nd one there can't at all hurt. and it removes that jumper from the equation. too.

while you are there, I'd remove one cap from each of the boards (the bulk caps right next to each other on each control board. you don't need that many, really. on my first proto I had none at all and my relay action was ok. having 1 per board when you have FOUR boards - is more than enough. you may even want to have just 1 per 2 boards. remember, this also 'hurts' startup as all those big caps in parallel just create a harder load to startup.

[Boinger]

So I did what you told me to removed 1 cap from each board... now im getting a hum in sound.

Still having the same problem as before and the difference in sound was more apparent... now however when i ran a scope with one board attached I was getting 4.5~ V across the relays.

The first 2 relays seem to not be firing at all the first one has no activity and the second one fires but not very often. No change measured across them in the scope.

One more interresting point when I was measuring across the relay it was showing 4.5v constant on the relays on the scope and when it clicked it dropped to 500 mv... Should this be happening? I figured it should be 0mv and spike to 4.5 V ?

[linux-works]

normally, *across* the 2 relay pads (if you put a DMM across the 2 relay wires) you should see very close to 0. 5v thru a 47ohm and into one wire, out the other wire, into a 47ohm and back up to 5v. that should add up to zero that assumes the ULN chips are sitting at very high Z until being told to 'short to gnd'.

maybe try other ULN chips? I use toshiba chips, I think. maybe the ULN you have has problems.

when you say you have hum now, that almost sound like the 5v supply is still straining. there is a connection between the attenuator ground and the lcduino/d1 logic ground - and it goes thru a ferrite wire/bead that I think I saw on your board. if you get hum in the audio path, your ground must be 'bad' OR maybe some of those probes you have soldered in place are picking up stray hum. I wouldn't worry too much about hum in the audio path when you have things set up in a test config with probes on it but I would worry if your ground is hummy.

a fancy supply is just not needed. the a10 has a small s25 7805 regulator that is a foot or less away from the lcd1 and the d1/d2 stack. if the regulator is putting out 5v and is kept pretty close and the ground is strong and also local (and not going all over the place) - and if the supply can handle 500ma or an amp as a surge at power up and maintain a few hundred ma during operation, things SHOULD work. people are not generally reporting problems if they keep to the design and not have overly long wires.

I've done lots of testing with just wall warts; but I always try to have the REGULATOR loop kept to a foot or less of wire. have whatever you want leading UP TO the regulator; but after that, I keep my ground short and my b+ also very short. when I do that, I can drive even 3 d1 at the same time (you saw the photo I posted).

so, try a different type of ULN chip (toshiba ones) and maybe that will help. before even doing that, does swapping some chips from other boards change things at all?

[amb]

update: linux-works got Boinger's boards and did some testing. Results are posted in this thread:
delta1-test-results-t1757.html

[linux-works]

pics of the broken trace that caused the last bit to not ever work:





I added the white wire to fix it. after I cleaned the board, I could finally tell that it wasn't a micro break but a whole pad was gone. that was enough to stop the relay from ever being reset. once it would set one way, it would never go back since 2 lines (one from each port expander and relay driver chip) is needed to flop the relay both ways.

fwiw.

[linux-works]

here is the test bed I'm using to test boinger's boards:



and here are 3 amp-meter readings in max-hold mode. first, the worst-case bootup current drain:



then the steady state 'no relays being changed' mode, lcduino is awake but user has not changed volume:



and finally, here is where I twist the knob and record the highest drain from any step to the next (63.5 to 64, I think):



about half an amp when TWO boards are in parallel (technically, not a legal config but it seems to work) and volume is being switched and under 200ma when 2 d1 boards and an lcduino are running, in standby. at bootup, well, its over 2 amps, or it can be. that's not to say you need that much, but if you have it, it will consume it for a short while (1-2 seconds or so).

[amb]

Those numbers look quite a bit higher than my own measurements, but it's probably due to the different LCD displays used. Linux-works' is a larger display of unknown specs, mine was one of the recommended low-power Newhaven units (which consumes only 20mA with the backlight on).

[linux-works]

that lcd does draw a bit more. for a single lcduino and single d1 board, its usually around 70ma on idle.

the bootup and knob-turning, though, are mostly the relays in action.

and again, in this case, double current is needed since the 2 boards are not being hit in sequence; they are being strobed in parallel.

its a torture test and people should follow the standard i2c addressing (each half of the board gets its own i2c addr via jumpers); but if the torture test works, the regular version should absolutely work well with even a small psu (you can see what I'm using; its a breadboard square off to the left with an lm317 style reg there and a skimpy heatsink.