Pedal Power Adapter Help (Point me in the right direction)

[Kevin Mitchell]

I've been reading as much research in the diy stompbox community as I can find but I figured the best way for an amateur like myself to find an appropriate answers is by asking here.

So this project of mine can go to a few directions, but the whole point is to get up to 24VDC and at least 300mA(power needed I think?) to my Neo Vibe circuit I am working on. Rather than buying a wallwart I would like to build my own adapter.

I've seen voltage doublers and they don't seem to hold up 100% to what this vibe pedal needs to run. Unless there is better way of converting 9V to 18-24V with appropriate amps?

Is there a layout already done for a voltage adjusting power supply? Like one that can go anywhere from 4V to 24V or something of the sort? This would be awesome because I could dial in where my pedals sound the best to ease my curiosity during debugging/testing.

Is a 24VDC wallwart adapter a difficult task? What should I consider?

Any suggestions or information regarding this idea is very appreciated. Thank you!

[Mark Hammer]

An 18V AC transformer will yield 24VDC, when rectified.  generally easier to find those in higher current, than 24VDC units.

[smallbearelec]

Hi Kevin--

Rather than buying a wallwart I would like to build my own adapter.
Is there a layout already done for a voltage adjusting power supply?

You will probably hear something like this from other people as well: Building a power supply that involves making your own connection to the AC line is a major piece of work, and Not a beginner project. There might be a vetted "build-it-this-way" design out there, but I would encourage you to get expert help before tackling such. In the case of the Neovibe, you really don't have to go that route. See next response.

Is a 24VDC wallwart adapter a difficult task? What should I consider?

The Neovibe board includes rectifier, regulator and filter, so needs only an AC input. This wall wart:

http://www.smallbearelec.com/servlet/Detail?no=1007

is good.

If you want to build a small, 9-volt supply for other purposes, try one of my Small Warts:

https://www.smallbearelec.com/Projects/SmWart/SmWart.htm

Regards
SD

[Kevin Mitchell]

Thanks for the response, smallbearelec.

I'm aware that I shouldn't work with AC transformer just yet. The specs on GeoFex's Neo Vibe part list reads
transformer: "14-16VAC or 20-24VDC wall xfmr."
power jack: "To match transformer"
Seeing how you could use either AC or DC I guess I felt open to creativity and not having to buy a power adapter. Maybe find a possible voltage doubler/trippler and use it with a Pedal Power 2 supply.
Idk. Anything but buying a wallwart! lol
I was hoping there was an easier way to power this thing up as well as having a little more fun building any possible power solution.

I'll still be looking around. But thank you very much for the tips and links to those pages! Expect an order from me soon!

[PRR]

Alarm systems use a 24 V AC wall-transformer. This has the wall-plug Built-In, you don't mess with high power or high voltage, and there is (should be) a safety-lab label on it.

The 24 Volts is not very lethal at all (do not let your cat chew on it!).

The size of the transformer means you can not get BIG power out of it, are unlikely to set your house on fire.

(The specifications are aimed at low-pay alarm installers who will make every sort of mistake and should not cause disaster or even real property damage. Same as you.)

Note that there are also 16VAC 24VA alarm transformers. You want _24_Volt_, typically 40VA. ("40VA" means it can output 40VA/24V= 1.6 Amps.)

24 Volts AC will rectify out to 35 Volts DC. You want the extra, because the Neo probably will be happier with a regulated supply. Wall-voltage variations and transformer sag make the "35VDC" wander from 36V to 28V. Run this to a LM7824 voltage regulator, which shaves-off everything over 24V, nice and solid.

You can probably find a voltage regulator board kit at CanaKits or Velleman.

[Kevin Mitchell]

Thanks that was an interesting read I really appreciate it!

I will look into this and see what I can do! Still have a bunch of research to do on transformers, AC/DC currents and so on. With your reply and info on the GeoFex site I'm pretty sure I can get this done. Otherwise there's a lesson I'm waiting to learn in the form of an electric shock.

Any further information is very welcome!

[Haze13]

Just wanted to add... Don't forget about large filter caps! ~ 1000uf after the diode bridge and 100uf-470uf after the Voltage Regulator.

[Kevin Mitchell]

Just wanted to add... Don't forget about large filter caps! ~ 1000uf after the diode bridge and 100uf-470uf after the Voltage Regulator.

Isn't there one already built into the Neo Vibe schematic on the Geofex site?

[Kevin Mitchell]

Hey guys I have question about wall adapters. I'm going to hold off on messing with raw transformers until I have the nerve to put together my own iso power supply.

Anyways here's my question; I found an adapter that puts out 24VDC 1AMP. After digging up whatever info I can I have no idea if too much amperage is a bad thing. I've read for the Neo Vibe 100mA is okay and 300mA is plenty enough. Will 1000mA compromise anything or will it work just fine?

Thanks fellas.

[induction]

The current rating just tells you how much current is available from the adapter. There's no risk from using one with more available current than you need. The pedals will draw what they need, no more.

[PRR]

> if too much amperage is a bad thing.

Your whole house is wired for 100 Amps.

In the middle of the night you have a few clocks and night-lights pulling maybe 2 Amps.

Here I'm wired for 100 Amps and I have never seen 30 Amps actually flowing. (The 100A is because homeowners just don't know their load, so the gear makers don't bother to make fuseboxes smaller than 100A.)

Your car has a 40 Amp alternator, but cruising with just ignition and radio it may only be supplying 5 Amps. (The 40 Amps is for when you have just cold-started and need to re-fill the starter battery, maybe with all the lights blazing and heater blower on high.)

Using a 1000mA supply for a 300mA load means "you paid too much", but (like houses) sometimes the cost is slim or none.

One aspect: the wires have to be good for the MAXimum current. Even if I know my house never sucks over 30A, *when* something goes wrong, 100 Amps or more will flow until the fuse blows, so I have to use fat wire (#2 not #8) so the wires will hold-in until the fuse blows. Down in the 1 Amp area, this is not an issue-- #30 might carry the current but you probably "need" #24 or larger to take the physical abuse.