DIY power supply for pedal board

[philbinator1]

Hey guys!

I've run out of room on my dc brick, so I'd like to build my own one...preferably with about ten 9V DC jacks and a maybe
2 DC jacks (hopefully switchable between 12-15-18V).  I'd like all of them to be isolated, to cut down on noise. 

Does anyone out there have any layouts/schematics etc for something like that?


Thanks!   

[Hides-His-Eyes]

Where are you going to get the transformer?

[philbinator1]

Um no idea!  I don't know a lot about power supplies; is a special transformer needed?  I have several
salvaged ones, and surely they sell them at Jaycar etc?  Or is building what I want an impossibility?

[fpaul]

I built three of the general guitar gadgets 4 isolated output boards and put them in one box. Eight outputs are 9volt and 4 are 18v (well, three actually because one's not working right).  Works great but not the cheapest solution ( 6 transformers).  I also made my own box so I'm not sure what you would use for that.

Just have to be careful with the AC supply wires and make sure everything is mounted securely.

[philbinator1]

I was hoping to keep it smallish...maybe around the size of a Pedal Power +2 or something.  My DC Brick is just
so nice and compact.

[Hides-His-Eyes]

DIY is good for a lot of things but making stuff smaller isn't usually one of them.

I really can't imagine you being able to build what you want in such a small enclosure.

[philbinator1]

DIY is good for a lot of things but making stuff smaller isn't usually one of them.

I really can't imagine you being able to build what you want in such a small enclosure.

How do they do it in the dc brick etc ?

[jkokura]

Open it up and see!

By the way... the new avatar is awesome phil.

Jacob

[philbinator1]

Open it up and see!

By the way... the new avatar is awesome phil.

Jacob

  Ya, buts my playings...is dildo's.

http://www.youtube.com/watch?v=qMewRRJCLm8

[Tonemonger]

Yeah I noticed that You'd shaved !

[philbinator1]

Yeah I noticed that You'd shaved !

..and became a cartoon!     Funny though, the goatee grows back every time I leave the forum...odd..

[G. Hoffman]

Have you read R.G.'s Spyder article on GeoFex?  Go do that, and you will understand what you need for a power supply. 

You are unlikely to be able to make it as small as a PP2 or a Brick.  They are making things with modern production techniques, and they are using custom transformers.  Expensive, but small.  I've looked inside my PP2+.  It made my eyes cramp.

That said, you can get a very useful transformer from Weber (or Small Bear carries them as well) which is designed for an isolated pedal power supply.  It won't give you the higher DC voltages you are after, but you could add a second small transformer for that if you wanted.  Just make sure you can get the current you need from it.  After that, its a pretty simple matter of a rectifier, some caps, and a regulator for each tap on the transformer.  Make sure you remember the fuse on the incoming AC line. 


Gabriel

[Ben N]

It may be worth your while to experiment a bit to see where isolated power benefits you and where it doesn't. There will almost certainly be some pedals that can happily share a daisy chain with no appreciable noise penalty, especially if the supply is regulated and well filtered, and others that really benefit from their very own tap. This could save you a lot of space, expense and trouble (even if it isn't a very DIY solution).

[philbinator1]

Hmm...not too keen on daisy chaining at all.  From past noise issues, I would only do it in desperation these days.  Which
I may have to do soon, having filled up my DC Brick.  Damn you DIY!!  [shakes fist at heavens]   

[JKowalski]

The most compact solution of average difficulty would be to wind your own transformer. It's really not as hard as it sounds. Basically you dismantle a transformer, unwind the secondary (leave the primary that connects to the wall voltage intact), wind your own secondaries on it, and reassemble. Depending on how the transformer you want to convert is constructed, this may be very simple or impossible.

Here's my 8 output 9V supply with a rewound transformer:



If you really want a small yet powerful power supply you would have to go into SMPS design or similar and that's a LOT of theory & experience to grasp, some people have entire careers devoted to it (plus it is dangerous stuff to DIY). But if you are sticking with linear, which really is the only option here, then you can't really shrink it down too much, you are limited by the size of your transformer and that is determined by the amount of power you want available. You have to decide where to draw the line, where the increase in size makes the increase in power not worth it.

[philbinator1]

Why do you re-wind the secondary?

[Hides-His-Eyes]

Hmm...not too keen on daisy chaining at all.  From past noise issues, I would only do it in desperation these days.  Which
I may have to do soon, having filled up my DC Brick.  Damn you DIY!!  [shakes fist at heavens]   

There are plenty of pedals that will quite happily share a daisy chain with no ill effects whatsoever, and there are plenty (Especially digital ones) which really won't.

Give it a try before you start spending silly money.

[JKowalski]

Why do you re-wind the secondary?

Transformers are fairly simple devices, you have a metal core, typically shaped like EI, they are called E-I cores because they are made of a bunch of E and I shaped thin slabs of magnetic-firendly material stacked together. Then you have the windings, which are enameled wire (insulated with a thin coating) wrapped around the center leg of the E in the EI shape. There are usually two windings, a primary winding and a secondary winding, but you can have as many secondaries as you'd like. The primary winding is hooked up directly to the wall, so you don't want to touch that winding - it is already made to safety standards and set up. The reason you want to unwind the secondary and put a new one on is you will NOT find what you are looking for in any transformer on the market. There is no transformer commercially available to do exactly what you want (there is one made for pedalboard supplies but it is only nine outputs for 9 volts I believe, it's called the WPDLXFMR-1), since in your case you would need twelve secondary windings at ~10VAC... So the solution is to get a transformer, take off whatever secondary it has on it, and wind twelve different secondary windings onto the core to get your twelve 10VAC outputs.

The transformer outputs a voltage based on a ratio of turns between windings. For example, a 120:1 turns ratio transformer will output 1VAC on the secondary when 120VAC is put into the primary. To get the 10VAC outputs with an already made primary, you wind say 10 turns onto the secondary, reassemble the core, and test the voltage on the output. Using the voltage you get on the test and knowing the number of turns it took to get that voltage, you calculate how many turns you need to get to 10VAC or whatever voltage you need (aim for a peak voltage 2-3 volts higher then the output you want to have, and then use a regulator to smooth it out and bring it down). THen begin the laborious process of winding them all.

[Mark Hammer]

My own recommednation is to simply throw together what I like to call a power distribution box. 

At its simplest, this is just a small plastic box with the appropriate jacks; basically a "multiple" for DC power.  Connect the distribution box up to all the elements of the pedalboard with suitable cables, and all you have to do is plug a wallwart into the box when it's time to play.  You can include an indicator LED to  let you kow when the power is live.

Alternatively, such a box can include various degrees and types of regulation.  So, you could plug an 18VDC wallwart into it, and provide down-regulation to 12 and 9v with some 3-pin regulators and suitable caps.

Or, you could plug the 9VDC adaptor of your choice into it and pack another 1000-2200uf  of capacitance in there to smooth out the ripple a little more.

Or, you could provide all the regulation in the box and plug an AC-output adaptor into it.

All of these can work just fine, depending on your needs.  The nice thing about this approach is that the box can be made as small as you need it to be if you don't have to include the actual transformer in it.

[slotbot]

Here's my 8 output 9V supply with a rewound transformer:

nice job! (does that say 20 A on the case? haha)