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Power supply recommendation Answered

I've been trying to collect info and guidance on how to build a portable and minimalistic power supply. I have in the past built other stomp boxes and small amplifiers (PCB kits) but never enough to learn how to read schematics or build from scratch, so I'm looking for something pretty detailed or simple enough. List of the technical and practical requirements: -Steady and safe current output for several hours straight; -Operating voltage: 3-4 to 15-17 volts; -Current: 2-3A; -1 voltage control potentiometer; -1 digital voltmeter; -1 output (1/4 jack); -1 pedal switch input (1/4 jack); -1 status LED; - Possibly external transformer (to keep it smaller and avoid overheating); -No vent holes; I have found similar builds (instuctables and YouTube), but never similar enough to be sure that putting that build in a smaller and sealed box would perform well and not overheat It seems weird to me that I wasn't able to find any kit or project for such a simple build. Below a link to an ideal result example https://thelondontattooconvention.com/suppliers/hard-craft-company-handmade-tattoo-power-supplies/

Discussions

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Jack A Lopez

2 months ago

I suspect this power supply in an artsy case,

https://hardcraftco.com/product/orange-sparkle-dea...

(Seriously? They call it, "Dear Concubine.")

has Chinese made modules inside, specifically a DC-to-DC buck converter or PWM converter, plus LED voltmeter module to display the output voltage.

Also there is likely another power converter not shown, an AC adapter, which converts AC mains power to some DC voltage corresponding to the highest voltage desired, e.g. 16 volts.

Then the buck or PWM converter converts that 16 volt DC input, to some DC voltage less than that, in the range 0 to 16 volts, adjustable by turning a potentiometer.

These modules, the DC-to-DC converter, the LED voltmeter, are sold on eBay, and they are inexpensive. The only downsides to using these modules: Documentation is sparse. They take weeks to arrive by mail, if you live anywhere far from China or Hong Kong.

And I am guessing you already know this, since you write, " I have found similar builds (instuctables and YouTube)"

You can't be bothered to link to those tutorials though.

Also you say these builds are unsatisfying to you, because they have vent holes, and you want your build to be small and sealed, like the ugly, "Dear Concubine" design, made by Hardcraftco, linked above.

My guess is the way Hardcraftco is dealing with heat in this design, is by bolting the main switching IC directly underneath that brass plate, with a thin layer of thermal grease in between the two, so the brass plate acts as a heat crude sink.

I am trying to think what else to mention. It is hard for me to guess, since many of these points may have been covered by tutorials you have already read and disliked.

The potentiometer, the big knob, is important. The value of that pot has to be same as the value expected by the module doing the power converting.

A lot of those modules, sold on eBay, have a built-in pot, for adjusting the output voltage, but that pot is this tiny little thing, made to be adjusted by a screwdriver. So the tiny pot has to be replaced with a big one with a knob on it.

There are also converter modules made with terminals to attach an external potentiometer, and I think the phrase that pays for searching those out, on eBay, is:

"adjustable converter external potentiometer"

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Downunder35mJack A Lopez

Reply 2 months ago

I got used to you coming up with odd solutions that other people miss but I have to ask:
How the heck do you find these things, especially considering the odd name? ROFL

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Jack A LopezDownunder35m

Reply 2 months ago

How does anyone find anything, aside from intuition, followed by actual searching of some kind?

Regarding my user name, it is one of those that has the form of a real name (i.e. given name + middle name + surname), but that is obviously fake because it is a bad pun of some kind.

Other examples include: "Rusty Steele", "Herb Gardener", "Robin Banks", "Forrest Burns", "Ellie Dee", and "Helen Highwater."

Although there are people out there, whose real names are actual goofy puns like that. Years ago, talk show host David Letterman would actually seek these people out, and have them on the show, usually as part of a "Top Ten" list. Each person, of these 10, would briefly step forward and say his or her own name, while at the same time, a picture of this person's drivers license, with everything blurred out except the name, would appear to the side, or another section of the TV screen, as proof it was real.

Or real enough for TV. Although I do not think is too far-fetched to believe there really are people walking the streets of English-speaking countries, with names like, "Harry Dick", "Teddy Bear", and "Ima Duck."

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Downunder35m

2 months ago

Back in the days we just used these adjustable transformers for model railways for these things.
Sadly they are now a thing of the past and getting quite expensive.
Modern electronics are now cheaper, more efficient, less reliable....

I was thinking of a route like this:
24V power supply from some old laptop, printer or whatever fits the amp requirements for you.
Then a step down converter with adjustable output, preferably with a big electrolytic capacitor and inductor behind to supress dirty stuff on the DC output.
Most of these converters won't come with a suitable potentiometer that can deal with constant handling, so it makes sense to replace it with a bigger metal type.
You might find some for free in old amps and such.
As Jack already mentioned the handling of heat can be a problem in a closed case.
The buck converters I have in use are either rated for low duty or come with some quite big heat sinks, one even has a temp controlled fan on it.
You only need a max of 3A, so if you select a converter rated for at least 5A the produced heat should be managable.
The tricky part with a sealed housing is to get rid of the internal heat.
That means that at least everything that already has a heat sink needs to be modified.
Easiest way I found is to get some thin copper from the scrap yard.
Be it an old hot water tank, a pot or whatever - you only need a small piece that can be flattened and cleaned.
I use an aluminium plate on the housing, preferably mounted above and not behind the cicuit board.
The copper sheet is then cut to suitable strips that connect the part that ha th heat sink with the sheet on top.
Only tricky part is to screw it together.
That is the reason why I solder the screw for the plate onto the copper strip.
Easy to feed through the hole in the top plate and a dome nut covers it.
A rough sanding and thin cover with matt black paint helps to drive the heat away from the plate.
For external connections like the footswitch I would try to salvage things from headphone connectors over thoses from discarded electronics (printer, scanner and so on) to modifying other stuff just for a weird look.
Sometimes I like to use E14 lamp fittings and an old lamp to make a screw connector that can handle a few more amps than other things.....