www.megadrum.info

Hi everyone,

I have a question about the external power option on the Synthex Kit v3.2 main board.
The documentation says 7V - 12V AC or DC.

But what about the current?
Say I want to use a 220V AC > 9V DC stabilized power adapter, what ampere range is safe to use?

funkystx wrote:Hi everyone,

I have a question about the external power option on the Synthex Kit v3.2 main board.
The documentation says 7V - 12V AC or DC.

But what about the current?
Say I want to use a 220V AC > 9V DC stabilized power adapter, what ampere range is safe to use?

A megadrum will run off usb power which is about 1/2 an amp. So anything over 500ma is fine. You can't have too many amps as the circuit will only use what it needs (most typical power adapters won't be rated for over 5-6 amps). So using the info you provided, minimum requirements would be 220v AC/9v DC/ 500ma.

jman 31 wrote:
A megadrum will run off usb power which is about 1/2 an amp. So anything over 500ma is fine. You can't have too many amps as the circuit will only use what it needs (most typical power adapters won't be rated for over 5-6 amps). So using the info you provided, minimum requirements would be 220v AC/9v DC/ 500ma.

Thanks for the info! It seems all so obvious, but I was a little confused by the fact that USB power is 5V and external power requires 7V - 12V.
I know USB power should be around 500mA, so it makes sense external power should provide at least the same.

And I guess I mixed up Volts and Amps thinking that I could fry the system by using too many amps.
It's starting to come back to me now.... all that knowledge is from way back, so I really have to dig deep! haha

Rens

The reason for the minimum 7 volts is that the power is running through an L7805 (5volt voltage regulator) after it is rectified with the 1N4007 diodes (see schematic). A voltage regulator typically needs a couple of volts more than it's rating to function properly. There are other variables at hand here, but that is the gist of it.