Author Topic: Power Supply: Build or Buy?  (Read 11752 times)

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Offline br4n_d0nTopic starter

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Power Supply: Build or Buy?
« on: May 03, 2023, 09:49:15 pm »
I could really use an adjustable power supply and since I'm new to electronics I don't know how practical it would be to try and build my own to fit my needs. My main concern is it being safe so I'd prefer not to get some cheap no name power supply that could start a fire or kill me.

I would like this to be more of general discussion to help others with a similar question, but I'll leave some specifics of what I'm looking for to help guide me in a good direction.

  • 24volts @ ~3amps (for powering a soldering iron)
  • 100-120volts @ low amps (gives me the ability to electroplate/anodize in the future)
  • Whatever voltage/amps I'll need in making some small electromagnets
« Last Edit: May 04, 2023, 12:28:16 am by br4n_d0n »
 

Offline David Hess

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Re: Power Supply: Build or Buy?
« Reply #1 on: May 03, 2023, 10:38:34 pm »
I would not combine such separate applications into one power supply.
 
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Offline BeBuLamar

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Re: Power Supply: Build or Buy?
« Reply #2 on: May 03, 2023, 10:47:40 pm »
The 100-120VDC power supply is kind of a specialty. I think you would want a separate unit for that. The 24VDC power supply are plenty perhaps buy a fixed 24VDC supply. I am sorry but please don't say Chinese when you mean bad products. They make products of all different level of quality.
 
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Offline AG6QR

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Re: Power Supply: Build or Buy?
« Reply #3 on: May 04, 2023, 12:16:11 am »
When I can find multiple commercial products which will basically fit my needs, I've always found that it's very hard to save money by building my own.  That's definitely the case with power supplies.

I think most electronics tinkerers ought to have at least one bench power supply that offers adjustable constant voltage regulation and adjustable constant current regulation.  It should probably have meters that show voltage and current. There are MANY companies that make many variations on this kind of supply.  They come in many quality levels, with many levels of voltage and current capability.  My most used unit is my antique linear HP E3610A which I picked up used for a bit over a hundred dollars.  That doesn't mean it's the best bargain for everyone, but it meets my needs, and the quality is excellent -- good enough that for almost any purposes, I can pretend it's perfect, at least within its voltage and current limits.

If you want to build a power supply as a learning exercise, it could be a good project. But it's likely to end up costing more and being of lower quality than a commercial supply. It might be worth it if you end up learning enough from the exercise, though.

Having said that, I agree that the 100-120V DC supply for electroplating is a specialized beast.  I don't have such a supply now.  My inclination, at least to start out for occasional use, would be to use a dozen or more 9V alkaline transistor radio batteries in series, to get the high voltage and low current. In addition to very low cost, it has the advantage that the internal resistance of those small batteries limits the current somewhat.  While it's not totally safe, at least an accidental short is unlikely to be as spectacular as shorting DC produced by rectifying mains power without proper current regulation. If I found that I wanted to do frequent electroplating, I'd look into other alternatives.


 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #4 on: May 04, 2023, 12:53:48 am »
Fixed 24VDC is easy to build, that's a good beginner project.

A basic adjustable power supply is not too hard, but if you have the means to get a commercial bench power supply that would probably serve you better.

100-120V is very unusual, I thought electroplating typically used just a few volts and anodizing is maybe 12V or a tad higher, are you sure you need ~100V+? That's typical if you want to work with vacuum tubes.
 

Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #5 on: May 04, 2023, 01:33:25 am »
Yeah, titanium takes higher voltages and caps out at around 120v
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #6 on: May 04, 2023, 02:43:24 am »
How much current does it take? You can get adjustable boost modules from China for a few dollars that will go up to a few hundred volts. You might also get away with using unfiltered rectified 120V from the wall with a resistor or lightbulb to limit the current.

Either way I would not try to accomplish both of these goals with a single power supply. One that is optimized to deliver high voltage is going to be poorly suited for low voltage applications and you don't want to forget that it's set to 100V and switch it on while connected to a 3.3V microcontroller board or something.
 

Offline Brumby

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Re: Power Supply: Build or Buy?
« Reply #7 on: May 04, 2023, 07:03:58 am »
Either way I would not try to accomplish both of these goals with a single power supply.
Neither would I.

Quote
One that is optimized to deliver high voltage is going to be poorly suited for low voltage applications and you don't want to forget that it's set to 100V and switch it on while connected to a 3.3V microcontroller board or something.
That was my first apprehension as well - and that sort of "oops" is bound to happen at some point.
 

Offline armandine2

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Re: Power Supply: Build or Buy?
« Reply #8 on: May 04, 2023, 09:34:29 am »
https://www.elektormagazine.com/magazine/elektor-199010/32232

I started building the elektor 400W power supply  :palm: but ran out of steam quite quickly - not a beginners project.

I've revisited it recently and was soldering smd components to meter PCBs last night.
In a closed society where everybody's guilty, the only crime is getting caught - Hunter S Thompson
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #9 on: May 04, 2023, 10:53:01 am »
My main concern is it being safe so I'd prefer not to get some cheap no name power supply that could start a fire or kill me.

A home made one is just as likely to be unsafe or burn the house down.

  • 24volts @ ~3amps (for powering a soldering iron)

You really can't go wrong with something like this: https://www.aliexpress.com/item/4000419022828.html

Meanwell are a respected brand and they have full protection against overloads/overheating/etc.

Anecdote: Two weeks ago I saw somebody in a classroom deliberately try to blow a fuse with one of those and fail. The PSU always shut down faster than the fuse could blow.

(The indicator LED on the PSU turned off and the fuse was fine.  :)  )

The fuse blew perfectly when we tried a different PSU
 
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Offline David Hess

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Re: Power Supply: Build or Buy?
« Reply #10 on: May 04, 2023, 12:53:21 pm »
I am sorry but please don't say Chinese when you mean bad products. They make products of all different level of quality.

Unfortunately distinguishing the good produces from the bad is practically impossible, making them all bad.  China has become the Nigerian Prince of counterfeit products, with companies like Ebay, Newegg (Chinese owned now), and Amazon helping.

If you want to build a power supply as a learning exercise, it could be a good project. But it's likely to end up costing more and being of lower quality than a commercial supply. It might be worth it if you end up learning enough from the exercise, though.

A variable bench power supply is an excellent learning project.  It is too bad that there are not any good kits.

I would also consider rebuilding an HP/Harrison power supply, or something similar that has full documentation.
 

Offline tunk

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Re: Power Supply: Build or Buy?
« Reply #11 on: May 04, 2023, 01:24:00 pm »
What's your soldering iron?
It may be able to run from an old laptop power brick.
The voltage will be lower (~19V), so heat-up will be slower.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #12 on: May 04, 2023, 02:01:33 pm »
What's your soldering iron?
It may be able to run from an old laptop power brick.

Or two old ATX power supplies in series.  :)
 

Offline BeBuLamar

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Re: Power Supply: Build or Buy?
« Reply #13 on: May 04, 2023, 02:31:15 pm »
I am sorry but please don't say Chinese when you mean bad products. They make products of all different level of quality.

Unfortunately distinguishing the good produces from the bad is practically impossible, making them all bad.  China has become the Nigerian Prince of counterfeit products, with companies like Ebay, Newegg (Chinese owned now), and Amazon helping.

/quote]


You can't too bad because even name brand power supplies are made in China too. You think this is a bad power supply that would burn down your house?
https://www.testequipmentdepot.com/bk-precision-1901b-programmable-switching-dc-power-supply-32v30a-120vac-line-input.html?ref=gbase&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZyxBpiROwMSLyV_I-WSqU-l_lfiNhWB-rO3-JCeLmJYt3EL1qJgSlsaAmdIEALw_wcB
And yes it's made in China.
« Last Edit: May 04, 2023, 02:35:40 pm by BeBuLamar »
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #14 on: May 04, 2023, 05:55:05 pm »
Everybody knows that when one speaks of "Chinese products" they are referring to the no-name domestic market junk that is prolific on ebay, aliexpress and so many others, not the high quality name brand stuff that is manufactured there.
 

Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #15 on: May 04, 2023, 07:29:49 pm »
The general consensus thus far seems to be for purchasing a power supply as there seems to be a lack of good info or kits out there for a beginner such as myself. However, if someone could find a really nice kit or great tutorial for an absolute beginner, I may take a look.

So, any recommendations for one $100 or less?
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #16 on: May 04, 2023, 07:53:23 pm »
The general consensus thus far seems to be for purchasing a power supply as there seems to be a lack of good info or kits out there for a beginner such as myself. However, if someone could find a really nice kit or great tutorial for an absolute beginner, I may take a look.

So, any recommendations for one $100 or less?

There's lots of modules on Aliexpress, eg. https://www.aliexpress.com/item/4000742314477.html

Quality varies but they all need some sort of external power supply to power them, typically with a voltage higher than the maximum desired output voltage.

I've got one of these: https://www.aliexpress.com/item/1005001530484759.html

It's really tiny and I can power it from a USB-C powerbank or a suitable phone charger up to 30V - portable bench supply! It works well enough but I don't think I'd use it as my main supply.

FWIW Dave did a series of videos on those modules:








« Last Edit: May 04, 2023, 08:23:26 pm by Fungus »
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #17 on: May 04, 2023, 07:54:49 pm »
Me? I wouldn't want to power my soldering iron from my bench supply - imagine having to swap the cables around every time you want to solder something, or be switching between soldering and powering. That would get old really fast.

Get yourself a fixed 24V supply for that.
 
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Offline nctnico

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Re: Power Supply: Build or Buy?
« Reply #18 on: May 04, 2023, 08:34:58 pm »
Be sure to get a linear power supply as your primary lab power supply. Switchers (which includes those dc-dc converter modules) output too much noise to make meaningfull measurements to a circuit.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #19 on: May 04, 2023, 08:59:47 pm »
Switchers can be very clean, it's all a matter of how well they are designed. Linear power supplies are easy to make quiet though.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #20 on: May 04, 2023, 09:33:55 pm »
Be sure to get a linear power supply as your primary lab power supply. Switchers (which includes those dc-dc converter modules) output too much noise to make meaningfull measurements to a circuit.

Depends on what you're building. Digital circuits won't care.
 

Offline nctnico

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Re: Power Supply: Build or Buy?
« Reply #21 on: May 04, 2023, 10:07:25 pm »
Be sure to get a linear power supply as your primary lab power supply. Switchers (which includes those dc-dc converter modules) output too much noise to make meaningfull measurements to a circuit.

Depends on what you're building. Digital circuits won't care.
Digital doesn't exist. As soon as you connect a scope to hunt down a problem, you can easely get a lot of noise on your display that is not coming from your circuit but from a switching PSU. So what is what?

Switchers can be very clean, it's all a matter of how well they are designed. Linear power supplies are easy to make quiet though.
No. I own and have owned quite a few of the high-end HP switching PSUs and none of them have a really clean output.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #22 on: May 04, 2023, 11:51:12 pm »
Yeah, I was thinking of going for a linear one.
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #23 on: May 05, 2023, 12:08:22 am »
No. I own and have owned quite a few of the high-end HP switching PSUs and none of them have a really clean output.

That doesn't mean clean switchers don't exist, merely that the specific models that you've had are noisier. For most things it doesn't matter, for some it does. It's certainly easier to find a linear supply with a really clean output but it isn't the only option.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #24 on: May 05, 2023, 06:26:58 am »
No. I own and have owned quite a few of the high-end HP switching PSUs and none of them have a really clean output.

I see the noise nannies are out again.

Stated use cases are:
Powering a soldering iron
Electroplating
Making electromagnets

At what point would 50mV of noise make the sky fall?

That doesn't mean clean switchers don't exist, merely that the specific models that you've had are noisier.

It also doesn't mean that somebody who wants to build their own from a kit can't add some filtering.
 


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