Author Topic: Power Supply: Build or Buy?  (Read 11747 times)

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Offline nctnico

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Re: Power Supply: Build or Buy?
« Reply #25 on: May 05, 2023, 09:21:45 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.
No, just common sense. I read: beginning with electronics. A linear Korad PSU costs about the same as a switching PSU. Due to the lower noise, the linear PSU is a much more versatile piece of equipment.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline Caliaxy

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Re: Power Supply: Build or Buy?
« Reply #26 on: May 05, 2023, 06:33:36 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?

For general use, I'd get a linear triple power supply, with +/- 0-15V for circuits that require differential power (e.g. op amps) and +5V (for logic circuits).

This kit on Amazon seems basic but OK. It provides everything you need, including transformer and enclosure, for under $80. You have to solder it yourself. Some users improved it over time (with multi-turn pots for finer voltage adjustment and output meters - read the reviews). It doesn't limit the current output, so you have to be careful. I have no experience with it.

https://www.amazon.com/Elenco-Triple-Output-Power-Supply/dp/B0002DT0GU/ref=sr_1_1?crid=1XLLSDE54UER8&keywords=elenco+triple+power+supply&qid=1683309302&sprefix=%2Caps%2C207&sr=8-1&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
 
If you are in US, you might find good deals on older HP triple power supplies on eBay, such as 6326B (if under $50) or (better) E3630A (if under $80-100). Make sure they are in good shape (working, with no missing knobs and/or broken posts). I used an E3630A for a long time and was happy with it. It's nice to be able to limit the current, to protect your circuits from yourself.

If you buy new, Korad KA3005D (~$110) is a more modern option (well regarded here), but it's only single output. I have one of these too, no complaints.

I wouldn't power my soldering iron from a bench power supply either. I'd buy a switching power supply for everything requiring high voltage/power output. Safer and simpler.
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #27 on: May 05, 2023, 06:45:35 pm »
My most used power supply is a switcher based 1.2-30V that I built myself out of a cheap module and a surplus power brick, it's convenient because it's a tidy little enclosure that I can carry around wherever I need it. Next is an old Heathkit linear triple bench supply, it's a bit lacking in terms of features, it doesn't have current limiting but the variable outputs are only good for 500mA so this isn't much problem in practice. I like it because it has real analog knobs that respond instantly. I also have a big Tektronix bench PSU which is linear with digital controls, it's very capable but the user interface is pretty terrible, it's the only power supply I've ever had to read the manual to figure out how to use it. There are too many cases where the same button does multiple things. The linear supplies I have are much cleaner than the switcher, but at least 90% of the time it doesn't matter for what I'm doing.
 

Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #28 on: May 05, 2023, 09:38:48 pm »
If you are in US, you might find good deals on older HP triple power supplies on eBay, such as 6326B (if under $50) or (better) E3630A (if under $80-100). Make sure they are in good shape (working, with no missing knobs and/or broken posts). I used an E3630A for a long time and was happy with it. It's nice to be able to limit the current, to protect your circuits from yourself.

These are stupid expensive right now on "theBay" for beat up and non-functioning ones... I  don't get it.  :palm:
 

Offline nctnico

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Re: Power Supply: Build or Buy?
« Reply #29 on: May 06, 2023, 12:19:12 am »
My biggest problem with the old PSUs is that these don't have accurate readouts. Nowadays a lot of circuits run from low voltages. For that you need at least 2 digits after the decimal point. 3.3V chips (for example) often have maximum operaring voltages of 3.6V. You can't adjust the voltage accurately enough using a moving pointer on a scale that goes to 20V / 30V.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #30 on: May 06, 2023, 04:56:54 am »
For general use, I'd get a linear triple power supply, with +/- 0-15V for circuits that require differential power (e.g. op amps) and +5V (for logic circuits).

This kit on Amazon seems basic but OK. It provides everything you need, including transformer and enclosure, for under $80. You have to solder it yourself. Some users improved it over time (with multi-turn pots for finer voltage adjustment and output meters - read the reviews). It doesn't limit the current output, so you have to be careful. I have no experience with it.

I wouldn't want a power supply that doesn't have readout of voltage and current. That's like using a CRO instead of a DSO.

Current limiting is fairly essential for me, too. Negative rail? Not so much. I rarely use op-amps and if I do I use R2R versions to avoid having to put fancy power supplies in the finished device.

The last part is just me, obviously, but the first part stands.

 

Offline David Hess

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Re: Power Supply: Build or Buy?
« Reply #31 on: May 06, 2023, 01:39:54 pm »
I wouldn't want a power supply that doesn't have readout of voltage and current. That's like using a CRO instead of a DSO.

I have enough multimeters that using a power supply without built in readouts does not bother me.  It is enough to have an indicator showing if the power supply is in current limit.
 

Offline bdunham7

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Re: Power Supply: Build or Buy?
« Reply #32 on: May 06, 2023, 02:22:35 pm »
  • 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

For  your 24V soldering iron, I'd get a dedicated switching supply.  I have one of these (not for soldering irons) and it seems pretty decent and is made in Taiwan.  It is DIN-rail mounted and so is intended for use inside a control panel.  You'd have to make up a box of some sort for it because the line voltage terminals are exposed.  It's not the only choice, but it is one I know will work.

https://www.ebay.com/itm/134508829833

Also, the much more powerful Meanwell LRS-350-24 that powers certain 3D-printers is also a possible candidate because they are widely available, work well and are pretty cheap ($35 on Amazon) due to their popularity.

For your electroplating, I'm assuming you want a limited current supply (a few mA) and I'd also recommend a simple, dedicated supply but this is one you can build.  I'd start with a small, isolated step-down transformer and then a voltage multiplier circuit. You can read the Wikipedia article on voltage multipliers and I've provided a link for what I think might be an appropriate transformer.

https://www.mouser.com/datasheet/2/410/F48_050_C2-781070.pdf

https://en.wikipedia.org/wiki/Voltage_multiplier

As far as electromagnets, you'll have to clarify how big, etc.  You want either something pretty well protected or something you can fix yourself since you can generate some pretty wicked inductive spikes with large coils. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline BeBuLamar

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Re: Power Supply: Build or Buy?
« Reply #33 on: May 06, 2023, 02:31:19 pm »
I don't see much point in using 24VDC power supply to power a soldering iron. Get an AC powered soldering iron and save the 24VDC iron for when you want to use it on battery.
 

Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #34 on: May 06, 2023, 04:20:06 pm »
I don't see much point in using 24VDC power supply to power a soldering iron. Get an AC powered soldering iron and save the 24VDC iron for when you want to use it on battery.

I've had the soldering iron for a few years now so purchasing another one would be a waste of money. Having a bench PSU that can do double duty when I feel like it would be more worth it IMO.
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #35 on: May 06, 2023, 05:50:00 pm »
I wouldn't want a power supply that doesn't have readout of voltage and current. That's like using a CRO instead of a DSO.

Current limiting is fairly essential for me, too. Negative rail? Not so much. I rarely use op-amps and if I do I use R2R versions to avoid having to put fancy power supplies in the finished device.

The last part is just me, obviously, but the first part stands.

Some of us are quite able to use a CRO effectively, or measure the output of a PSU with a multimeter if we really need a precise voltage. The one PSU I have with an analog meter goes up to 20V and I can quite easily set it to 3.3V accurately enough in most cases. It's just a matter of knowing what you're doing and how to use the tools you have at your disposal. "A poor craftsman blames his tools."

Negative rail is absolutely essential for some projects, and not just those with op amps, while single rail op amps do exist, they have limitations. A split supply is hardly a "fancy supply", it's trivial to integrate into the finished product. I typically use a DC-DC converter module, they're tiny, cheap and effective. Not that it really matters, virtually all multi-output bench supplies have independent outputs that can be wired in series.
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #36 on: May 06, 2023, 05:52:08 pm »
I don't see much point in using 24VDC power supply to power a soldering iron. Get an AC powered soldering iron and save the 24VDC iron for when you want to use it on battery.

I've had the soldering iron for a few years now so purchasing another one would be a waste of money. Having a bench PSU that can do double duty when I feel like it would be more worth it IMO.

So lash up a salvaged transformer, rectifier and filter capacitor (assuming the iron contains electronic temperature regulation) and call it done. If the iron is not a temperature controlled soldering station then IMO it's not really worth having except as a backjup.
 

Offline nctnico

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Re: Power Supply: Build or Buy?
« Reply #37 on: May 06, 2023, 05:55:23 pm »
I wouldn't want a power supply that doesn't have readout of voltage and current. That's like using a CRO instead of a DSO.

Current limiting is fairly essential for me, too. Negative rail? Not so much. I rarely use op-amps and if I do I use R2R versions to avoid having to put fancy power supplies in the finished device.

The last part is just me, obviously, but the first part stands.

Some of us are quite able to use a CRO effectively, or measure the output of a PSU with a multimeter if we really need a precise voltage.
That becomes a nuisance quickly. Especially when you are working on projects that need a couple of different voltages. Been there, done that. Even considered buying even more DMMs but made a much wiser decision in the end: buy PSUs that have proper metering built-in. Saves a lot of time & effort so I can concentrate on getting my circuits going.
« Last Edit: May 06, 2023, 06:02:16 pm by nctnico »
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 #38 on: May 08, 2023, 04:44:17 am »
As a newcomer and barely a hobbyist, this stuff is way overpriced for me. I may have to wait a long time or win some sort of contest to get something good.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #39 on: May 08, 2023, 06:48:04 am »
Some of us are quite able to use a CRO effectively, or measure the output of a PSU with a multimeter if we really need a precise voltage.

Do you also use a slide rule instead of a calculator? They're good enough for most jobs.
 
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Offline J-R

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Re: Power Supply: Build or Buy?
« Reply #40 on: May 08, 2023, 07:35:28 am »
New 40W Hakko soldering iron for $7.80: https://hakkousa.com/910-convertible-40w-soldering-iron.html (free shipping @ $25)

Cheapest adjustable power, recycle a laptop power brick (~20V/3-5A) and combine it with an LM2596S board:  https://www.mtnelectronics.com/index.php&product_id=136
Also, tons of other LM2596S boards out there on ebay with different options, such as with a built-in LED display.
Add some capacitance on input/output to clean things up and replace the trimmer pots with real ones and you've got something basic for nearly no money.


Some other places to window shop:
https://www.jameco.com
https://www.tequipment.net
https://www.testequipmentdepot.com
https://www.arrow.com

For used (prices are cheaper direct compared to their ebay stores):
https://www.ntc-tech.com
https://equiptek.com/000.htm
https://www.sglabs.it/en/

Of course:
https://www.digikey.com
https://www.mouser.com


Ultimately, I think you're stuck and you'll just have to buy one of those cheap bench supplies on Amazon that may or may not burn your house down...  They are typically in a metal box so the odds are low...
 

Offline nctnico

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Re: Power Supply: Build or Buy?
« Reply #41 on: May 08, 2023, 07:46:12 am »
As a newcomer and barely a hobbyist, this stuff is way overpriced for me. I may have to wait a long time or win some sort of contest to get something good.
What is your budget? The PSUs from Korad are a good start without breaking the bank.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline tooki

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Re: Power Supply: Build or Buy?
« Reply #42 on: May 08, 2023, 07:46:42 am »
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.
Indeed, I’ve had great experiences with Mean Well, too.

But why suggest buying on aliexpress? Mean Well is sold by all the major distributors (ensuring it’s genuine) at lower prices.
 

Offline tooki

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Re: Power Supply: Build or Buy?
« Reply #43 on: May 08, 2023, 07:52:58 am »
As a newcomer and barely a hobbyist, this stuff is way overpriced for me. I may have to wait a long time or win some sort of contest to get something good.
What is your budget? The PSUs from Korad are a good start without breaking the bank.
Yep. A Korad KA3005P is my “daily driver” bench supply at home, and it works well without taking up too much space. (For example, my Agilent U8001A sits unused on the shelf most of the time because it’s so deep; I can’t dedicate that much bench space to it.)
 

Online 5U4GB

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Re: Power Supply: Build or Buy?
« Reply #44 on: May 08, 2023, 08:59:12 am »
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.

For power supplies specifically it's actually not that hard, just look at the components and layout around the mains side of the circuit and you can get a fairly good idea as to whether it's properly designed and built or not.
 

Online 5U4GB

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Re: Power Supply: Build or Buy?
« Reply #45 on: May 08, 2023, 09:02:01 am »
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.

I was going to comment on that too but checked the OPs usage and it doesn't seem like there's much there that'll be too critical about noise levels, or even exact voltage levels.
 

Offline David Hess

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Re: Power Supply: Build or Buy?
« Reply #46 on: May 08, 2023, 09:06:35 am »
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.

For power supplies specifically it's actually not that hard, just look at the components and layout around the mains side of the circuit and you can get a fairly good idea as to whether it's properly designed and built or not.

The criteria that I start with is whether the power supply has a service manual, with schematics and layout.  It is not like there is some secret power supply IP which needs to be protected.
 

Online 5U4GB

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Re: Power Supply: Build or Buy?
« Reply #47 on: May 08, 2023, 09:14:45 am »
As a newcomer and barely a hobbyist, this stuff is way overpriced for me.

So that's a related question, why are most of the name-brand PSUs so incredibly expensive?  I saw a Rigol product ad the other day and their lab power supplies cost as much or more than a lot of their scopes, and those are some of the cheaper ones out there.  I realise there's a bit more than an LM723+2N3055 in there, but does that really justify a four-digit price for a dual 0-32V 3A PSU?
 

Offline gjvdheiden

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Re: Power Supply: Build or Buy?
« Reply #48 on: May 08, 2023, 09:50:14 am »
You get what you pay for.

I've 2 Korad power supplies (single and a double), doing just fine for me. I'm just learning and making some simple boards. Instead of a fancy power supply I invested in nice test leads. For what I'm doing, the power supply provides a very stable output and it has current limiting. Started with a single one, nice size. Soon this was annoying enough and bought a double (and a +5V without current limit which I never use) power supply.

There's a new one out, Korad KA3005PS. Suppose to have less noise according to the advertisement.
 

Online 5U4GB

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Re: Power Supply: Build or Buy?
« Reply #49 on: May 08, 2023, 10:24:02 am »
There's a new one out, Korad KA3005PS. Suppose to have less noise according to the advertisement.

Is the -PS a custom version of the -P for Eleshop?  That seems to be the only place that carries it, even the Korad product page doesn't mention it.

For those who don't mind switchers, the Gophert NPS-1601 is compact, fanless, and gets reasonably good reviews.
 


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