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12v euro -> 15v MOTM adapter?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author 12v euro -> 15v MOTM adapter?
tommy.york
Does anyone know of a small, DIY (or inexpensive) 12v to 15v MOTM adapter?

The inverse (MOTM to Euro) exists...
mnml
I had a quick look at the MC34063 chip. One thing to look for in these magical ICs is output ripple. The spec sheet says unfiltered it's 400mV (a half volt of wiggly jiggliness); filtering gets you 40mV, which is also too high. There are low-noise chips but I haven't yet seen one that manages the kind of current necessary.
sduck
How about the Mean Well DCW08A-15 - mouser part # 709-DCW08A-15 ? It should have enough power to get your FS1a going.
gasboss775
mnml wrote:
I had a quick look at the MC34063 chip. One thing to look for in these magical ICs is output ripple. The spec sheet says unfiltered it's 400mV (a half volt of wiggly jiggliness); filtering gets you 40mV, which is also too high. There are low-noise chips but I haven't yet seen one that manages the kind of current necessary.


This filter gave 4.2mV peak to peak, with a 400mV 50Khz input. Its very important to use a low ESR capacitor + the inductor needs to be a power inductor, not one of those little axial ones.

tommy.york
gasboss775 wrote:
This filter gave 4.2mV peak to peak, with a 400mV 50Khz input. Its very important to use a low ESR capacitor + the inductor needs to be a power inductor, not one of those little axial ones.


Like Mouser 983-T60405-A6161X003?

sduck Thank you. I think I'm going to get the parts for both these potential solutions and try them on a breadboard. Gotta relearn how to breadboard at some point anyhow!
gasboss775
tommy.york wrote:
gasboss775 wrote:
This filter gave 4.2mV peak to peak, with a 400mV 50Khz input. Its very important to use a low ESR capacitor + the inductor needs to be a power inductor, not one of those little axial ones.


Like Mouser 983-T60405-A6161X003?


No those are for filtering line power. These would be better ( and cheaper )

Mouser: 871-B82111EC25
mnml
Curious how the power issue works out...
tommy.york
mnml wrote:
Curious how the power issue works out...


Well, I breadboarded the simplest of all the solutions, the DC/DC converter (sduck's recommended Mean Well DCW08A-15) alone. Just to confirm that I'm doing this correctly, I connected:

Euro +12v to DC/DC +in
Euro -12v to DC/DC -in
DC/DC COM to MOTM Ground
DC/DC +15v to MOTM +15v
DC/DC -15v to MOTM -15v

So, no ground from Euro. Just ground from the DC/DC converter. I measured the voltages and everything seemed fine. (What does COM stand for?)

Datasheet says (max) ripple / noise is 60mVp-p. Should I add gasboss775's filter? mnml: I'm going to breadboard the MC34063 circuit tonight after work, with gasboss775's filter.

Last question: how do I measure ripple / noise? What's an acceptable value for that? The only testing equipment I have is an old oscilloscope and a hand multimeter. edit: found some good explanatory videos on the youtubes.
sduck
You can and should attach the ground from your euro supply to the MOTM ground. You don't want a floating ground - it's not actually grounded that way. (My terminology is probably way off here)
tommy.york
sduck wrote:
You can and should attach the ground from your euro supply to the MOTM ground. You don't want a floating ground - it's not actually grounded that way. (My terminology is probably way off here)


Makes sense. I was only able to get +/- 15V readings using COM as ground, but I think it's because I was probing the wrong pin on the Eurorack 10-pin connector (I think one column was connected and the other wasn't / not all of them are connected, maybe?).

Will connect Eurorack ground -> MOTM ground and COM -> MOTM ground, and make sure that those two connections are themselves connected.
tommy.york


Alright, bread boarded the DC/DC converter with the (half pi?) filter from gasboss775. I'm a little out of my depth on measuring the noise / ripple, but it looks like maybe ~20mv of ripple / noise at both +15v and -15v. Those capacitors are low ESR.

My jumpers didn't come from Amazon until late, so no chance to play around with the MC34063. I looked through the data sheet again and it looks like I'm going to need to do some spreadsheeting to calculate all the component values (for 12v to 15v step-up at ~125ma on each rail)... And also create the circuit twice, once for 12v to 15v, and once for -12v to -15v (need to re-study voltage to really understand how those two are different).
enoughstatic
tommy.york wrote:
... And also create the circuit twice, once for 12v to 15v, and once for -12v to -15v (need to re-study voltage to really understand how those two are different).


Glad to have found this thread (thanks sduck for the reference).

However, tommy.york : It looks like this DC-DC module should have both polarities (bi-polar), so are you sure you need another one? Or did I misunderstand you?

As for this experiment, I'm happy to see you conduct it as I'm currently seeking out the same solution, but for a slightly different system to module conversion.
tommy.york
enoughstatic wrote:
tommy.york wrote:
... And also create the circuit twice, once for 12v to 15v, and once for -12v to -15v (need to re-study voltage to really understand how those two are different).


Glad to have found this thread (thanks sduck for the reference).

However, tommy.york : It looks like this DC-DC module should have both polarities (bi-polar), so are you sure you need another one? Or did I misunderstand you?

As for this experiment, I'm happy to see you conduct it as I'm currently seeking out the same solution, but for a slightly different system to module conversion.


That question (about how to adapt the circuit in the MC34063 data sheet) was re: the MC34063 chip, not the circuit / filter for the DC-DC converter. DC-DC converter + filter looks like it's working.

Just a heads up, I'm moving at the beginning of July so am trying to wrap up projects before I pack them up to move them. The breadboarded 12v -> 15v converter works, so it'll be enough to run / calibrate my Haible frequency shifter. After I move, I'll pick this up again and hopefully figure out something around the MC34063 chip!
I'm hoping to use this as an opportunity to hone my breadboarding, then Eagle skills. Rockin' Banana!
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