Author Topic: Power Supply: Build or Buy?  (Read 11741 times)

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Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #50 on: May 08, 2023, 12:24:26 pm »
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?

This is exactly what I'm talking about; I highly doubt the parts and all that amount to even half the price of these "higher end" brands. Seems like huge price gouging to me, but I'm new to this so...
 

Offline gjvdheiden

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Re: Power Supply: Build or Buy?
« Reply #51 on: May 08, 2023, 12:40:15 pm »
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.

I did got the info from Eleshop, but they seem to carry to versions. KA3005PS, which according to Eleshop is just a new version and then the KA3005PE-AN. The latter is an Eleshop only version.

The knob seems a little bit better too.
 

Offline gjvdheiden

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Re: Power Supply: Build or Buy?
« Reply #52 on: May 08, 2023, 01:09:58 pm »
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?

This is exactly what I'm talking about; I highly doubt the parts and all that amount to even half the price of these "higher end" brands. Seems like huge price gouging to me, but I'm new to this so...

5U4GB was talking about a Rigol. These usually are built to a price. The only 4 digit Rigol I can find is the Rigol DP2031. Just over 1300 euro. That thing can do arbitraty waveforms, 1mV/1uA precision, 10A max per channel (banner specs), has a TFT, various control inputs and then some. I don't think I could built that cheaper myself. You pay, you get.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #53 on: May 08, 2023, 01:50:35 pm »
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.

I don't want to recommend any particular distributor.

It's also going to depend on where you live...  :-//
 

Offline mawyatt

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Re: Power Supply: Build or Buy?
« Reply #54 on: May 08, 2023, 03:45:52 pm »
The first thing to consider for a newcomer to electronics is how many channels and what voltage current levels are necessary. As all of us at one time were newcomers "been there done that" and quickly found out for general purpose work dual channels is a must, at minimum +-20V at 1A.

We also found out that all switching PSs make additional noise above a linear type, some are so bad as almost useless for anything other that driving a motor!! Altho some recent quality switching PS are not too bad and could be useful for even some analog type work.

The additional cost one finds in a quality lab/bench type PS like the mentioned Rigol (and others) is they are linear types, use of torrid type transformers (low magnetic field leakage), multiple independent channels, very low output noise levels, utilize precision DACs and ADCs so the outputs are spot on (both voltage and current), don't have turn ON or OFF overshoot/undershoot (disastrous for sensitive semiconductors), behave nicely when engaging Over Current or Voltage limits, easy to read digital displays (some have/allow much larger fonts) and have multiple means to remotely communicate.

All these features cost in design time, assembly, components (and customer service) and this is reflected in the end user cost.

Since most of us have "been there done that", a wise newcomer would learn from others and select a PS that's linear and has a couple outputs capable of producing clean accurate voltages and currents, maybe +-20V and 1A from a reputable OEM source (or used).

One thing a newcomer may not recognize, but will quickly learn (usually the hard way!!), everything in electronics starts with the Power Supply, wether a Battery, Mains PS or Solar Source, and a cheap, noisy, inaccurate PS soon finds its way to the trash. This is especially true as one gains knowledge in electronics and becomes "seasoned" :-+ 

Best,
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Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #55 on: May 08, 2023, 07:49:15 pm »
The first thing to consider for a newcomer to electronics is how many channels and what voltage current levels are necessary. As all of us at one time were newcomers "been there done that" and quickly found out for general purpose work dual channels is a must, at minimum +-20V at 1A.

We also found out that all switching PSs make additional noise above a linear type, some are so bad as almost useless for anything other that driving a motor!! Altho some recent quality switching PS are not too bad and could be useful for even some analog type work.

The additional cost one finds in a quality lab/bench type PS like the mentioned Rigol (and others) is they are linear types, use of torrid type transformers (low magnetic field leakage), multiple independent channels, very low output noise levels, utilize precision DACs and ADCs so the outputs are spot on (both voltage and current), don't have turn ON or OFF overshoot/undershoot (disastrous for sensitive semiconductors), behave nicely when engaging Over Current or Voltage limits, easy to read digital displays (some have/allow much larger fonts) and have multiple means to remotely communicate.

All these features cost in design time, assembly, components (and customer service) and this is reflected in the end user cost.

Since most of us have "been there done that", a wise newcomer would learn from others and select a PS that's linear and has a couple outputs capable of producing clean accurate voltages and currents, maybe +-20V and 1A from a reputable OEM source (or used).

One thing a newcomer may not recognize, but will quickly learn (usually the hard way!!), everything in electronics starts with the Power Supply, wether a Battery, Mains PS or Solar Source, and a cheap, noisy, inaccurate PS soon finds its way to the trash. This is especially true as one gains knowledge in electronics and becomes "seasoned" :-+ 

Best,

I think this is quite helpful for someone new such as myself. Thanks  :-+
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #56 on: May 08, 2023, 08:20:23 pm »
Something else worth noting is that you will probably end up with several power supplies of various types, it's hard to have too many. I have a mix of commercial, kit, and home built power supplies and I use all of them. When I was a kid I mostly used batteries and salvaged wall warts, I still do for some things. Then I moved on to building my own PSUs with 3 terminal regulators, and then I received an old Heathkit bench PSU as a gift which I still use. That can only do 500mA so I built several other 12V and 5V power supplies over the years and later picked up a big beefy Tek bench supply. You don't have to spend too much time finding the one power supply that will do everything, you start with what you can afford that fits the needs of the projects you want to work on and go from there.
 

Offline dobsonr741

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Re: Power Supply: Build or Buy?
« Reply #57 on: May 08, 2023, 08:34:24 pm »
Newcomers needs a fix point to learn and build their lab experience. Power supply is one of the best fix point, one that is professionally made and have the right features.
It's easy for us to forget, who got formal education into electronics, what was our first initiation into instruments. It was certainly not a DIY, it was this power supply.
Still a good starter at 0-25V, 0..1A and 5V fixed at 0..1A, even it was made 40 years ago.
« Last Edit: May 08, 2023, 08:38:15 pm by dobsonr741 »
 

Online 5U4GB

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Re: Power Supply: Build or Buy?
« Reply #58 on: May 09, 2023, 05:20:57 am »
use of torrid type transformers

I've always maintained that buying your electronics off Pornhub is a bad idea :-).
 
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Online 5U4GB

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Re: Power Supply: Build or Buy?
« Reply #59 on: May 09, 2023, 05:35:54 am »
The only 4 digit Rigol I can find is the Rigol DP2031. Just over 1300 euro. That thing can do arbitraty waveforms, 1mV/1uA precision, 10A max per channel (banner specs), has a TFT, various control inputs and then some. I don't think I could built that cheaper myself. You pay, you get.

Ah, sorry, the wording was a bit ambiguous, the Rigol sentence and the following one were separate comments.  For the Rigol it was the DP-832, which cost more than the different models of DS-1000 listed next to it.  It does have a lot of bling in there but then so do the scopes, and do you really need all that in a power supply whose principal job it is to just provide X volts at Y amps?
 

Offline gjvdheiden

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Re: Power Supply: Build or Buy?
« Reply #60 on: May 09, 2023, 08:15:34 am »
The only 4 digit Rigol I can find is the Rigol DP2031. Just over 1300 euro. That thing can do arbitraty waveforms, 1mV/1uA precision, 10A max per channel (banner specs), has a TFT, various control inputs and then some. I don't think I could built that cheaper myself. You pay, you get.

Ah, sorry, the wording was a bit ambiguous, the Rigol sentence and the following one were separate comments.  For the Rigol it was the DP-832, which cost more than the different models of DS-1000 listed next to it.  It does have a lot of bling in there but then so do the scopes, and do you really need all that in a power supply whose principal job it is to just provide X volts at Y amps?

All in the light of this topic, starting out and as a hobby.

A Rigol DP832 costs a bit under 500 euro here (the Netherlands). I didn't compare them with others, so there might be better suited ones for the price, but it isn't a waste either. Because it is such a fundamental instrument. But I would put my money on a better scope or function gen if I could spend more. My scope is an analog Hameg from '87 bought it from a school, it works.

If you're starting out, I think it is good to start with something simple. Indeed, you don't need this. If you start out simple, you can always expand with a more expensive one by the time you do need one. By that time you actually need one, you'll also actually know where to look for. But when starting out, like you said, just need x voltage at max y amps. That's the sensible way, but it's a hobby, doesn't have to be all sensible. The goal is to have fun. You might just want to play with the buttons on a Rigol DP832 all day long. Or just have more fun when actually using it. Who knows but you.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #61 on: May 09, 2023, 02:18:07 pm »
If you're starting out, I think it is good to start with something simple. Indeed, you don't need this.

Yep.

If the two jobs at hand are 24V for a soldering iron and 110V for electroplating then you don't need a fancy supply at all. Get a 24V switching supply (soldering irons don't care about 50mV of noise) and look into getting 110V somehow (a boosted old wall wart?)

Total outlay: About 35 bucks.

Then you can dream about spending 500 Euros on a Rigol (or whatever).

(A Rigol isn't going to do the 110V anyway...)
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #62 on: May 10, 2023, 01:41:20 am »
Yeah the two main applications listed aren't really bench supply territory anyway. It would be a bit silly to tie up an expensive bench supply running a soldering iron, and as mentioned earlier, 100V+ is a specialty thing you won't find in many bench supplies that are also suitable for low voltage work.
 

Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #63 on: May 10, 2023, 03:36:22 am »
No one has touched on the electromagnet part; it will probably be dependent on its specifications, but I was curious if it's more voltage or current dependent.
 

Offline bdunham7

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Re: Power Supply: Build or Buy?
« Reply #64 on: May 10, 2023, 03:42:47 am »
No one has touched on the electromagnet part; it will probably be dependent on its specifications, but I was curious if it's more voltage or current dependent.

Small electromagnets are not particularly challenging and I think you'd typically use a CC (current regulated) supply.  But the specifics are important--you can generate huge transients with electromagnets and simple but specialized circuits would be best to drive them.
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.
 
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Offline tautech

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Re: Power Supply: Build or Buy?
« Reply #65 on: May 10, 2023, 04:18:57 am »
No one has touched on the electromagnet part; it will probably be dependent on its specifications, but I was curious if it's more voltage or current dependent.
Back EMF can be a huge problem and it's wise when using a PSU for powering such to take precautions to avoid subjecting the PSU outputs to back EMF. Regen motors also present the same issues and even reverse voltage protection can be exceeded and output stages damaged.
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Offline br4n_d0nTopic starter

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Re: Power Supply: Build or Buy?
« Reply #66 on: May 10, 2023, 06:57:55 am »
Both of you, thanks for letting me know. I was going to just start playing around with some small ones without very much knowledge and it seems like that could've been damaging.
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #67 on: May 10, 2023, 07:07:50 am »
You'll probably be fine, I played with electromagnets frequently when I was a kid and I never hurt anything although I did get a few shocks while leaning the principal behind a boost converter in the process. The large spike occurs when you open the circuit, which you'd normally do by disconnecting the wire that goes to the power supply and then the spike can't get to the power supply anyway.

The strength of the magnetic field depends on the number of turns and the current through the turns. The more turns you have, the more voltage you will need to get the current up.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #68 on: May 10, 2023, 07:33:32 am »
No one has touched on the electromagnet part

It also won't care about noise from a switching supply.

Small electromagnets are not particularly challenging and I think you'd typically use a CC (current regulated) supply.

Yep. You control the magnet strength by controlling the current.

A CC supply will help you do that and not overheat the wires.  :)

The power supply you need for this will depend on how many amps you want. A lot of amps quickly becomes expensive.  :popcorn:
 

Offline mawyatt

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Re: Power Supply: Build or Buy?
« Reply #69 on: May 10, 2023, 12:29:20 pm »
No one has touched on the electromagnet part; it will probably be dependent on its specifications, but I was curious if it's more voltage or current dependent.
Back EMF can be a huge problem and it's wise when using a PSU for powering such to take precautions to avoid subjecting the PSU outputs to back EMF. Regen motors also present the same issues and even reverse voltage protection can be exceeded and output stages damaged.

So true, and one MUST pay attention to such or likely fry the PSU!!

Relays are basically solenoids electromagnetically, and should always utilize a current recovery diode to give the interrupted current a nice place to go as it decays, Ldi/dt can and will wreak havoc with things!!

We are working with a controller for a high pressure DC motor that requires ~50 amps, so you can bet we are paying attention to back EMF as this can send the PS (and maybe yourself) to the grave if not properly attend too :o

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline tkamiya

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Re: Power Supply: Build or Buy?
« Reply #70 on: May 10, 2023, 12:43:46 pm »
I think buy or make decision is all depending upon one's purpose, interest, and ability.  If making one interests you, by all means, make one.  Don't forget buying used one either.  Older HP power supplies are big and heavy but generates very clean output.  I'd choose them over brand-new inexpensive ones.  Just for fun, I've purchased a $50 unit from Amazon.  Awful build quality and output was full of noise.  I wasn't expecting much for the price but even then, it was much worse than my expectations.  I sent it back for refund.

What's the use-case for 100V DC power supply?  What kind of specifications are you looking for?  That one may be a bit trickly.  Off the top of my head, I don't know of any that covers that range and even relatively affordable.

Good luck.
 

Offline Fungus

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Re: Power Supply: Build or Buy?
« Reply #71 on: May 10, 2023, 12:45:55 pm »
So true, and one MUST pay attention to such or likely fry the PSU!!

It won't be easy, there's usually a big capacitor across the output that will absorb it.

Relays are basically solenoids electromagnetically, and should always utilize a current recovery diode to give the interrupted current a nice place to go as it decays, Ldi/dt can and will wreak havoc with things!!

I like to use LEDs so you can see them flash when the spikes hit.

Being able to see the spikes really helps teach people the need for protection.
 

Offline james_s

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Re: Power Supply: Build or Buy?
« Reply #72 on: May 10, 2023, 05:30:12 pm »
It won't be easy, there's usually a big capacitor across the output that will absorb it.

Not in a bench supply, a big capacitor across the output reduces the effectiveness of current limiting in the event of a short circuit.

In ~35 years of playing with electronics I have never managed to damage a PSU by playing with inductive loads though.
 

Offline tautech

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Re: Power Supply: Build or Buy?
« Reply #73 on: May 10, 2023, 08:46:14 pm »
No one has touched on the electromagnet part; it will probably be dependent on its specifications, but I was curious if it's more voltage or current dependent.
Back EMF can be a huge problem and it's wise when using a PSU for powering such to take precautions to avoid subjecting the PSU outputs to back EMF. Regen motors also present the same issues and even reverse voltage protection can be exceeded and output stages damaged.

So true, and one MUST pay attention to such or likely fry the PSU!!

Relays are basically solenoids electromagnetically, and should always utilize a current recovery diode to give the interrupted current a nice place to go as it decays, Ldi/dt can and will wreak havoc with things!!

We are working with a controller for a high pressure DC motor that requires ~50 amps, so you can bet we are paying attention to back EMF as this can send the PS (and maybe yourself) to the grave if not properly attend too :o

Best,
What PSU are you using for that development Mike ?

Have you looked at the SPS5000X range ?
I've been using my 40V 60A unit for charging solar array batteries lately....a remote installation so powered with a genset.
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Offline mawyatt

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Re: Power Supply: Build or Buy?
« Reply #74 on: May 11, 2023, 02:50:25 am »

What PSU are you using for that development Mike ?

Have you looked at the SPS5000X range ?
I've been using my 40V 60A unit for charging solar array batteries lately....a remote installation so powered with a genset.

The Korad KWR102, but it's not enough for the higher current pump motors which may need up to 50 amps! We should have more data on the motors soon to help with the decision, and the SPS5000X might be a candidate.

Best,
« Last Edit: May 11, 2023, 02:52:18 am by mawyatt »
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