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Sounds like its deffo the Power adapter not having 'nuff juice.
As USB ports deliver between 500mA and 900mA(depending on the version) you'd need a power adapter that conforms within those values.As you seems to be drawing a lot out of it with leds and all, go for the top values given !!

so i've bought an adapter that gives out 12V & 1A, i've tried it out but the problem still remains...  smiley-cry

why is this happening?!
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fro the arduino website
Quote
USB Overcurrent Protection
The Arduino Mega has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port, the fuse will automatically break the connection until the short or overload is removed.
source: http://arduino.cc/en/Main/ArduinoBoardMega

so (if i've got this right) the usb won't ever deliver more than 500mA.
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Backfeed to the USB port at the PC, not the supply from the PC to the 'duino..?

Check the true current consumption by getting a multimeter set to mA between the supply and arduino (put it between VIN pin and the supply).
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Ok lets clear a couple things.
I was right in what i said that depending on the version will vary from 500mA to 900mA.
USB power is quite clean compared to a cheap power adaptor kind we find on the shops built in china ( ill give u an example- same as you built something, all sounded top,  with a wall adapter, noise comes).
As said before you need a good decoupling, the cleanest psu u can get, and preferably a metal enclosure to avoid emf interference ).
Look for hot to filter hum and ground noise, as theres los of tutorials on how to, and decoupling of course !
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i just found out that when i power the arduino sequencer using usb from my pc, if the computer is charging (attached to an external power supply) the synth starts going crazy, the same way it would if the arduino itself were powered from an external power supply.
simply disconnecting the laptop from it's external source solves the issue.

That suggests to me that the problem IS a ground loop. Laptop power supplies normally have a connection between the ground pin of the socket and the negative side of the output.

To verify this, try plugging the laptop power supply into a switched power socket. If the problem is caused by a ground loop, then it will occur whenever the laptop power supply is plugged into the mains power socket, whether or not the socket is switched on. But the problem will go away when you unplug the laptop power supply from the mains power socket.

Once you confirm that the problem is a ground loop, here are some things you can try:

1. Run the synth and the Arduino from the same mains power socket, by using a 2-way adapter or a socket strip.

2. Instead of connecting Arduino ground directly to synth ground through the cable that connects them, put a 100 ohm resistor in series with this ground connection. This will prevent large currents flowing through the ground loop.
« Last Edit: May 01, 2012, 11:06:55 am by dc42 » Logged

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ok so here is a schematic of the whole thing.
it also contains some features i still haven't implemented, but that i would like on the final design, plus i've written some notes here and there to explain things better... smiley-wink

i really hope this will somehow help understand what's wrong.

p.s. since it's my first creation ever i really appreciate general feedback or comments on it  smiley-lol

To verify this, try plugging the laptop power supply into a switched power socket. If the problem is caused by a ground loop, then it will occur whenever the laptop power supply is plugged into the mains power socket, whether or not the socket is switched on. But the problem will go away when you unplug the laptop power supply from the mains power socket.

i thought i had a switched power socket somewhere at home, but turns out that i don't.
tomorrow i'll buy one and try, and we'll see what happens

* sequencer_schem.pdf (2520.86 KB - downloaded 20 times.)
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A few comments on the schematic:-
1) You will never read anything from the rotatory encoder because the arduino inputs go directly to ground.
2) There is no pull up on A15 so you will not be able to read that switch state once it is not connected to ground.
3) S18 appears to connect the CV to the Gate out, or Gate Out1 - is this correct?
4) Not sure why R55 is fitted, it doesn't seem to be doing much.
5) You can get + / - 12V if you have an AC output wall wart and half wave rectify the signal for each rail. Although this seems to be a lot of fuss for just one op amp. Maybe you could bias the op amp's ground to 2.5V but I haven't looked at the data sheet to see if that amp can work off +/- 2.5V or a 5V single rail.
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i just found out that when i power the arduino sequencer using usb from my pc, if the computer is charging (attached to an external power supply) the synth starts going crazy, the same way it would if the arduino itself were powered from an external power supply.
simply disconnecting the laptop from it's external source solves the issue.

That suggests to me that the problem IS a ground loop. Laptop power supplies normally have a connection between the ground pin of the socket and the negative side of the output.

To verify this, try plugging the laptop power supply into a switched power socket. If the problem is caused by a ground loop, then it will occur whenever the laptop power supply is plugged into the mains power socket, whether or not the socket is switched on. But the problem will go away when you unplug the laptop power supply from the mains power socket.



so i tried to do what you suggested to see if it was a ground loop, but turns out that when the socket is off, the problem on the synth disappeares. so it's not a ground loop.
what now?


i was also thinking that if we were not to find a solution, i could run the whole sequencer from batteries. i already tried to power the arduino using a 9v battery and it gave no problems at all.
i would prefer the battery to be rechargeable trough wallwart, without having to take it out every time.
and i wouldn't use the sequencer when it's charging, so it wouldn't create any problems synthwise...i could live with that.

what do you guys think?is it doable? is it worth it?



A few comments on the schematic:-
1) You will never read anything from the rotatory encoder because the arduino inputs go directly to ground.
2) There is no pull up on A15 so you will not be able to read that switch state once it is not connected to ground.
3) S18 appears to connect the CV to the Gate out, or Gate Out1 - is this correct?
4) Not sure why R55 is fitted, it doesn't seem to be doing much.
5) You can get + / - 12V if you have an AC output wall wart and half wave rectify the signal for each rail. Although this seems to be a lot of fuss for just one op amp. Maybe you could bias the op amp's ground to 2.5V but I haven't looked at the data sheet to see if that amp can work off +/- 2.5V or a 5V single rail.

thanks for your comments. i fixed the problems on the schematic (i actually wired the encoder right on the arduino, and it works great!)




and sorry for the late answer
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