Author Topic: Please recommend switching power supply  (Read 2341 times)

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Offline eeguyTopic starter

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Please recommend switching power supply
« on: February 23, 2024, 02:25:58 am »
Hello, I am looking into purchasing a switching power supply (48VDC, 150W) to provide power for two motor controllers. I was recommended a Mean Well LRS-150-48 but it does not have a hole to plug in the power cord. What options do I have? Any other good products of very similar capabilities?
 

Offline Whales

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Re: Please recommend switching power supply
« Reply #1 on: February 23, 2024, 02:37:42 am »
Quote
but it does not have a hole to plug in the power cord.

Do you mean that it doesn't have an IEC power connector?

A lot of 48V power supplies will have screw terminals for bare wires, not an IEC power plug.  They're targeted at equipment installers and technicians, not consumers.

You might be able to find some in a "laptop brick" style form factor (plastic case with an IEC power connector), but they'll probably cost more.  Check digikey, element14, mouser, RS-components and the other usual suspects.
« Last Edit: February 23, 2024, 02:39:22 am by Whales »
 
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Offline eeguyTopic starter

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Re: Please recommend switching power supply
« Reply #2 on: February 23, 2024, 03:01:01 am »
I think so. Are there commercially available adapter/case with IEC power slot and perhaps also terminals cover that I can add to those 48V power supplies?

I searched Amazon for bench switching power supply at 24-48V but they only have one set of outputs. I need to drive two motor controllers from the same power supply. As for stores like digikey, it looks like unless I am willing to pay over $220, there is no 48VDC with dual outputs of at least 6A.
« Last Edit: February 23, 2024, 03:06:53 am by eeguy »
 

Offline Whales

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Re: Please recommend switching power supply
« Reply #3 on: February 23, 2024, 03:26:39 am »
You can buy "panel mount" IEC power connectors that are designed to go onto the side of a metal box.  Sadly cutting the right size and shape hole is a pain without the right tools (drill bits + sheet metal nibblers).

In the hobbyist 3d printer world we cheat by 3d printing screw terminal covers and IEC connector mounts for these power supplies.  This isn't heat proof, fire proof or otherwise safety approved (but when dealing with CNC-controlled soldering irons that self-feed fuel you tend to have to supervise the machines anyway).

Why do you need an IEC power plug?  Would wiring a normal power lead (with powerpoint plug on one end) be good enough?  Then perhaps put it in a metal box with the power cord travelling through a gland as you only need to drill a round hole in the box for this to work.

 
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Offline eeguyTopic starter

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Re: Please recommend switching power supply
« Reply #4 on: February 23, 2024, 05:39:29 am »
I used to make my own PC using those power supplies which came with an IEC power connector and an ON/OFF switch. So those Mean Well ones look a bit strange to me.

Do you mean do what the gentleman showed in the video (from 8:30)?

At Home Depot, shall I look for Heavy Duty or Medium Duty Extension Cord? What product/brand and wire gauge (in.) do you recommend?
What is powerpoint plug?



« Last Edit: February 23, 2024, 05:48:40 am by eeguy »
 

Offline Whales

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Re: Please recommend switching power supply
« Reply #5 on: February 23, 2024, 09:28:45 am »
Computer ATX power supplies are aimed at consumers, so they have an IEC connector and no easy way of electrocuting yourself.

Yes I mean the style of power supply that's shown in that video, with screw terminals to wire the power.  The target market are people who are confident and safe doing this wiring, not consumers.  Eg cabinet/control technicians, manufacturers, electricians, etc.  That's why it looks strange to you.

If you're not confident in doing this then I recommend you find someone with more experience to help you out.  Mains electricity is dangerous and there are subtle mistakes you can make wiring these power supplies, especially since the low voltage output and high voltage input are right next to each other.  The last thing you want is for the metal case or connectors on something to become live and dangerous.  Also you will probably want to manually ground other parts of your setup (I can only guess without seeing everything).

This sort of power cord:



Cut the IEC plug off and wire it directly to the power supply.  For 150W you will find that any gauge of power cord will be enough, but to be certain you can compare the amperage rating written on the side of the cord with what's written on the power supply.

I suggest this sort of cord simply because people tend to have lots lying around already.  The alternative of making your own cable from scratch adds more chance of making mistakes (and is more work).
« Last Edit: February 23, 2024, 09:36:28 am by Whales »
 
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Offline eeguyTopic starter

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Re: Please recommend switching power supply
« Reply #6 on: February 23, 2024, 02:30:22 pm »
Thank you for your suggestions.

What is the name of the orange plastic protective strip that is partially covering the ports?

Is the 3D printed route safer? Any recommended design? A quick search showed some of the following:

https://www.thingiverse.com/thing:4350646
https://www.printables.com/model/79287-slim-meanwell-lrs-350-psu-cover

Besides lower cost, how is this type of Mean Well power supplies compared with lab bench power supplies used in schools? I got one many years ago. There are knobs that I can use to adjust the voltage and in some cases current. Values are shown on the front panel. Why these Mean Well PS have no such user adjustable voltage and current knobs? Do they just provide the max voltage and max current?
« Last Edit: February 29, 2024, 05:18:22 am by eeguy »
 

Offline Whales

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Re: Please recommend switching power supply
« Reply #7 on: February 24, 2024, 12:37:58 am »
That small orange translucent plastic protective strip comes with the screw terminals.  Some screws terminals will have them, others won't.  They're not a full solution, but they do make things a little bit safer.

Those 3d printed ones you link to are what I was thinking.  Sadly most 3d printer filament is not firesafe (not self extinguishing) and start to soften at around 60degC (can collapse and cause shorts/fires).  For one-offs that you keep an eye on they're fine, but if you're making this for someone else then I'd try to do something better.

> Besides lower cost, how is this type of Mean Well power supplies compared with lab bench power supplies used in schools?

N.B. MeanWell is just one (popular) brand.  There are cheaper and more expensive options for these perforated chassis screw-terminal power supplies.  I don't know if there is a better or more common term to describe them.

An adjustable lab bench power supply can work, but there are a few potential gotchas.

A power supply that only needs to supply one voltage will be better optimised (cheaper, smaller, simpler, longer life, higher power efficiency).  The transformer only needs two windings and their ratio can be more optimal, it doesn't need relays to switch transformer taps, there are less parts to fail, transient responses can be better tuned, etc.  Or in English: the more specialised you are the better you can do that one job, the more generalised you are the less well you can do any particular job (but you can do them all).

Many bench lab power supplies are fully isolated (that's why on the front panel the earth banana jack is separate to the negative banana jack).  The perforated chassis screw-terminal style power supplies are not isolated, output ground is mains ground.  You probably don't care for your application.

A lab bench power supply will have both constant-voltage and constant-current feedback control.  A perforated chassis screw-terminal one instead only controls a constant-voltage; if your load draws too much current then it will switch off completely (Over-Current-Protection or OCP) instead of gradually reducing output.  (An exception are some LED power supplies in the same metal box form factor, but that's another story).

Knobs on lab bench power supplies can be banged, knocked or their pots can fail over time (potentially then sending way too high of a voltage into your devices).  Also if they use encoders instead of pots then they must store and remember the settings between power cycles, which sometimes they fail to do.  You don't want to turn your stuff back on and find out the power supply only wants to output 1V at 1A (or requires pressing an "enable" button manually).
 
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Offline eeguyTopic starter

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Re: Please recommend switching power supply
« Reply #8 on: February 24, 2024, 05:00:53 pm »
At one point, motor manufacturer suggested using only one power supply (a Mean Well) to control 2 pairs of stepper motors when I mentioned that I want to synchronize their movements. However, later on they said that it does not matter whether I use one Mean Well, two Mean Well or lab bench PSU from Amazon. In practice, which is better?

I read some reviews on lab bench power supplies (those below US$100) on Amazon and Youtube. Some users mentioned that even there are fine control knobs, they cannot generate the exact voltage they specified. If that happens, I suppose the two motors may not perform the same as they get different voltages. Will such subtle differences affect the actual performance?
 

Offline Whales

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Re: Please recommend switching power supply
« Reply #9 on: February 24, 2024, 10:33:20 pm »
Those are not simple questions.  It depends on a lot of factors, including your motor controller design, wiring and physical loads.

I recommend reading up on stepper motor control loops and the datasheet for your motor drivers (as a start).
 
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Offline Someone

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Re: Please recommend switching power supply
« Reply #10 on: February 24, 2024, 11:08:11 pm »
I searched Amazon for bench switching power supply at 24-48V but they only have one set of outputs. I need to drive two motor controllers from the same power supply.
Why the need for a single supply with multiple outputs? What is special about the motor controllers that they need this configuration/wiring ?

You're jumping way ahead of what you understand and are just getting confused.

Some of us have memories:
https://www.eevblog.com/forum/renewable-energy/mean-well-lrs-350-24/
 
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Offline The Soulman

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Re: Please recommend switching power supply
« Reply #11 on: February 24, 2024, 11:43:45 pm »
MW GST160A48



You'd need to get a matching connector for the output to connect to your motor drivers.

But maybe you are more the bench/lab power supply type of person that prefers binding posts to hookup the output wires? 
« Last Edit: February 24, 2024, 11:55:13 pm by The Soulman »
 

Offline eeguyTopic starter

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Re: Please recommend switching power supply
« Reply #12 on: February 25, 2024, 03:52:18 pm »
I am trying to buy something that is future proof so I can use in different projects.
 

Online Gregg

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Re: Please recommend switching power supply
« Reply #13 on: February 27, 2024, 05:21:45 pm »
If you are looking for a versatile switching power supply with nice to have voltage and current limiting in a compact case ready to go; you might consider a Gophert.   Here is an example: https://www.eevblog.com/forum/testgear/gophert-cps-6017-0-60v-0-17a-1000w-real/
I have a 0-60V 5A one.  Voltlog has a YouTube review of a lower power model:
 
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Offline Faringdon

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Re: Please recommend switching power supply
« Reply #14 on: February 27, 2024, 05:33:22 pm »
Pse forgive me, but i believe The answer has already been given above.....just buy a plastic box and cut a hole in  it for a chassis mount IEC connecter.
Cut the  hole by eg drilling multiple holes and then needle filing the plastic dross between the holes.
'Perfection' is the enemy of 'perfectly satisfactory'
 
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Offline eeguyTopic starter

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Re: Please recommend switching power supply
« Reply #15 on: February 29, 2024, 04:51:39 am »
Pse forgive me, but i believe The answer has already been given above.....just buy a plastic box and cut a hole in  it for a chassis mount IEC connecter.
Cut the  hole by eg drilling multiple holes and then needle filing the plastic dross between the holes.

What is the purpose of a plastic box? Is it to reduce the chance of me accidently touching the terminals?

OK. I have decided to get a Mean Well power supply just for the current project. I already have a lab bench PSU. If I need one more for other projects, I will buy another one later.

I went to Amazon and saw some IEC power connectors with a switch. How come almost all of them are for 250V rather than 110/125V used in North America? Any recommended brand and product?  I don't know if those made in China products have passed some electrical regulations before being sold in North America.

« Last Edit: February 29, 2024, 04:56:38 am by eeguy »
 

Offline Faringdon

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Re: Please recommend switching power supply
« Reply #16 on: February 29, 2024, 08:55:09 am »
yes, to stop touching, you dont need the box if you dont want.
'Perfection' is the enemy of 'perfectly satisfactory'
 
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Offline eeguyTopic starter

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Re: Please recommend switching power supply
« Reply #17 on: March 03, 2024, 10:15:54 pm »

This sort of power cord:

(Attachment Link)

Cut the IEC plug off and wire it directly to the power supply.  For 150W you will find that any gauge of power cord will be enough, but to be certain you can compare the amperage rating written on the side of the cord with what's written on the power supply.


By amperage rating written on the power supply, do you mean the input amperage rather than the output amperage? For the LRS-350-24, is it better to buy a power cord of 18AWG or 16AWG?

https://www.meanwell.com/Upload/PDF/LRS-350/LRS-350-SPEC.PDF
 


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