Power Regulation Situation

[GibsonGM]

Hi,

I'm converting an Easyvibe for use with a wallwart...got my jack in there ok, it's switching out the battery.  I have a 9VDC 500mA transformer I'd like to use, but of course it puts out like 16 volts with no load.  Since the EV has a measured draw of about 5mA pulses, this won't decrease enough to be around 9-10V if I use it (already tried it, the LEDs don't oscillate - but it didn't break *yet*).   

What are the options here?  This would be a good wall wart to use for several pedals in parallel due to its ampacity, but I don't want to zap anything.  If i put a regulator in series with the PS inside the EV, it'll be useless with a 9v battery.  Should I switch in a regulator circuit?  Maybe a zener or something?  Maybe run the adapter to a power distribution 'pedal', regulate it there and distribute to my pedals?

I almost always use batteries, trying to get into the whole adapter thing (9v's are getting expensive now that I have lots of stuff on the board!).  I'd like to see how others solve this issue.
Thanks

[db]

I would buy a regulated supply.

If you are determined to use your existing unregulated supply then you need a 7809 regulator or something similar, and, as you say you want to use it for a number of effects, then you may as well put the regulator inside a separate box.  The problem is that you need a minimum of 11 volts into your regulator for it to work and if your unregulated supply dips below this at 500mA or whatever your full load requirement is then, unfortunately, it isn't much use.

[GibsonGM]

Thanks, dB.
Yeah, it's probably not a bad idea to just grab one of those multiple-plug regulated supples for use with stompboxes.   I had thoughts of using a zener diode with 100 ohm series resistor, but the power supplies wouldn't match well (battery/adapter)...one would starve the circuit, the other kick it in the teeth.  I could hard-wire the adapter to the vibe and build the circuit in-place, then no battery.  PITA.
Sometimes it's easier to buy, I guess!   

[Bucksears]

I just came across this thread while looking for info on the Easyvibe.

Do you need a regulator if using a 9V wall-wart with the Easyvibe?

I was having problems with the 470uF cap (that faces the 9V rail) heating up to the point of explosion last time; I thought it was something to do with something shorting out somewhere, so modified the PCB so the parts/rails are more spread out and I can make the pads a little larger. I'm still populating the board right now, but if I'm going to have to configure it to have a voltage regulator in there, I might reconsider this altogether.
Thanks,
- Buck

[R.G.]

What are the options here?  This would be a good wall wart to use for several pedals in parallel due to its ampacity, but I don't want to zap anything.  If i put a regulator in series with the PS inside the EV, it'll be useless with a 9v battery.  Should I switch in a regulator circuit?  Maybe a zener or something?  Maybe run the adapter to a power distribution 'pedal', regulate it there and distribute to my pedals?

1. You need a regulator.
2. Use a 7809 three terminal regulator. They're easy and cheap.
3. The schematics are on GEO, and also many other places. You need the 7809, two capacitors and one diode.
4. One 7809 will supply up to 1A. The regulator will fall out of regulation when your power supply gets below 11V.
5. A cheap wall wart is not worth risking your pedals. Do this right. Get a wall wart that is rated at 11-12Vdc and a regulator. Then enjoy good clean power forever, no batteries. Goodwill often has wall warts for $1-$2 each, at least here. There is often a huge selection. Ask your friends and neighbors if they have orphan wall warts. It's a good bet.

I was having problems with the 470uF cap (that faces the 9V rail) heating up to the point of explosion last time; I thought it was something to do with something shorting out somewhere, so modified the PCB so the parts/rails are more spread out and I can make the pads a little larger. I'm still populating the board right now, but if I'm going to have to configure it to have a voltage regulator in there, I might reconsider this altogether.

Caps do this under three circumstances:
1. They're already damaged
2. They are inserted backwards
3. They are being supplied more than their rate votlage.

A short across the cap will not over heat the cap. It may damage other stuff, but the cap sees 0V. A short TO the cap may over volt it, though.
Why not use a 78L09? This is a TO-92 package regulator that can provide up to 100ma. You can stick one of these almost anywhere. It's ideal for single pedal regulation - which is really close to what it was designed for.

[Bucksears]

Thanks, R.G. I'll look into using a 7809; I think I might have some stashed somewhere in a parts bin.

(I know this is going to sound naive, but...) Given that the original layout uses a 9V battery, would there be that much difference in using a (Godlyke Power-All) daisy-chained power source that I would NEED to have a regulator?

- Buck

[R.G.]

I don't know about the Godlyke. I have heard some people use it with good results.

I do know that the 1Spot was designed for doing exactly this, and if you use the 1Spot it will definitely run a lot of pedals. Probably more than you have.

[GibsonGM]

Sweet...my Vibe is eating batteries, LOL. I try to leave it out of the chain until the set with the live Hendrix stuff...