# HELP!!! Power Supply Troubles!!!



## devils4ever (Feb 17, 2020)

So, I finally got my CNC electronics done (YEAH!) and I'm ready to add the ball screws, mounts, etc.

However, I'm having real issues with the motor power supplies. I'm using two 350 W (48 V, 7.3 A) switching power supplies from Automation Technologies bought via eBay.

I have them wired for 120 V with one powering the NEMA 34 motor and the other powering both NEMA 23 motors. I can't get them to consistently power on. I had trouble with one from the start that would only power on once every 10 tries or so. Now, that one is powering on consistently. The other PS was solid at first, but now it won't come on at all. I've tried removing the load and it seems to have no affect.

I'm at loss trying to figure this out. There's no power switch and both are set to 120 V.

Anyone else have this trouble? I'm ready to toss them across the room! The seller is willing to refund my money.


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## ttabbal (Feb 17, 2020)

Get a refund or swap them out with the vendor. I have one from them and it works great all the time. A power supply should never act like that, if it does, it's got issues.


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## JimDawson (Feb 17, 2020)

Switching power supplies are not the best for motor power.  I would send them back and buy this one https://www.automationtechnologiesi...gulated-625w-48vdc13a-input-120vac-or-230vac/

My experience with Automation Technologies is they have good customer service.


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## devils4ever (Feb 17, 2020)

ttabbal said:


> Get a refund or swap them out with the vendor. I have one from them and it works great all the time. A power supply should never act like that, if it does, it's got issues.



I was planning on sending the first one back, but now the other is doing the same thing. It makes me think I'm doing something wrong.


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## devils4ever (Feb 17, 2020)

JimDawson said:


> Switching power supplies are not the best for motor power.



I agree, but it doesn't turn on when I have no load on it either. Makes no sense!


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## JimDawson (Feb 17, 2020)

devils4ever said:


> I agree, but it doesn't turn on when I have no load on it either. Makes no sense!



Sounds like a bad power supply, not unheard of.

Are your drivers limited to 48V?


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## devils4ever (Feb 17, 2020)

JimDawson said:


> Sounds like a bad power supply, not unheard of.
> 
> Are your drivers limited to 48V?



But, both of them?

The DM542T is rated 50 V max and the DM860T is rated at 100 V max.


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## JimDawson (Feb 17, 2020)

Not sure why both would fail.  I assume your input voltage to them is correct.

In that case I would run the DM860T at near 100VDC, your motor performance will be much better.  

I would still use toroidal power supplies for motor power, they are almost bullet proof.


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## devils4ever (Feb 17, 2020)

JimDawson said:


> https://www.automationtechnologiesi...gulated-625w-48vdc13a-input-120vac-or-230vac/



It seems this power supply would provide enough power for all three motors. Correct?


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## JimDawson (Feb 17, 2020)

devils4ever said:


> It seems this power supply would provide enough power for all three motors. Correct?



Yes, it should be more than enough.


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## spumco (Feb 18, 2020)

Switching power supplies sometimes need a load to 'turn on'.  I had a similar problem with a brand-name PS where it wouldn't turn on if I didn't have enough of a load attached (a single LED or relay coil wouldn't do it).  

Solution was to add a big resistor to the output and just ground the resistor.  Calculated the resistance needed and got a 2W one which could deal with the heat - looks like one of those big power resistors built in to a heatsink.

Check the power supply _*minimum current*_ spec - that's what you need to provide as a load before it turns on.

And, as usual, Jim is on the money.  If you can swing it you want a toroidal power supply for the drives.  They turn on without issues and handle back EMF (decel of an axis) better.

-R


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## devils4ever (Feb 18, 2020)

I'm going to see if I can return these and replace with the unregulated 625 W power supply.


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## devils4ever (Feb 18, 2020)

spumco said:


> Switching power supplies sometimes need a load to 'turn on'.  I had a similar problem with a brand-name PS where it wouldn't turn on if I didn't have enough of a load attached (a single LED or relay coil wouldn't do it).
> 
> Solution was to add a big resistor to the output and just ground the resistor.  Calculated the resistance needed and got a 2W one which could deal with the heat - looks like one of those big power resistors built in to a heatsink.
> 
> Check the power supply _*minimum current*_ spec - that's what you need to provide as a load before it turns on.



I looked at the datasheet and I couldn't find a minimum current spec.

However, I had them connected to the motor drivers and they still wouldn't reliably turn on. Maybe, the motor drivers have a very light load on the power supplies until the motors are activated?

In any case, I'm ready to switch to the unregulated power supply.


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## shooter123456 (Feb 18, 2020)

devils4ever said:


> I looked at the datasheet and I couldn't find a minimum current spec.
> 
> However, I had them connected to the motor drivers and they still wouldn't reliably turn on. Maybe, the motor drivers have a very light load on the power supplies until the motors are activated?
> 
> In any case, I'm ready to switch to the unregulated power supply.


It sounds like something might be wrong.  My supplies powered up without problems when nothing was connected and I never had an issue with them not turning on.  Can you post pictures of your connections and check that the polarity is correct?


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## devils4ever (Feb 18, 2020)

Hmmm. I already pulled them out.

But, I connected the 120 VAC to the proper terminals (line and neutral) with ground to the proper terminal. I used my Fluke DMM to make sure the L and N terminals were getting 120 VAC. I got nothing on the 48 VDC terminals and the little LED was off. This was without load and with load.


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## markba633csi (Feb 18, 2020)

If the sense terminals (+,-) are strapped properly on the output then there really isn't anything else you can do except return them
-mark


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## devils4ever (Feb 18, 2020)

I don't think there are sense terminals. Here's the link to the power supply I'm using.


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## RJSakowski (Feb 18, 2020)

It sounds like an intermittent short in the wiring.  Have you tried powering the supplies up with nothing attached to the output terminals?


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## devils4ever (Feb 18, 2020)

Well, I tried and tried just now and I could not get the power supplies to fail!

I did it at least 25 times on both power supplies and they came on every time. They were on my bench with no load and I waited different amounts of time between tries and it never failed. I don't get it. This is so frustrating.

I'm sure if I put them back in, they will start acting up. They did fail on my bench before though.

ARGH!


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## Boswell (Feb 18, 2020)

If they work Out-of-Circuit and fail In-Circuit. then I would suspect that you have a short and the pwr supply protection circuit is kicking in.


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## RJSakowski (Feb 18, 2020)

I still say there is a short somewhere.  How about your mounting screws?  The spec lists specific lengths for the screw depth.  If too long a screw is used, there is a possibility of an internal short.


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## devils4ever (Feb 19, 2020)

Boswell said:


> If they work Out-of-Circuit and fail In-Circuit. then I would suspect that you have a short and the pwr supply protection circuit is kicking in.



I've had them not turn on with and without a load. It didn't seem to matter.


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## devils4ever (Feb 19, 2020)

RJSakowski said:


> I still say there is a short somewhere.  How about your mounting screws?  The spec lists specific lengths for the screw depth.  If too long a screw is used, there is a possibility of an internal short.



Yeah, I thought about that. My mounting screws are 3/8" long and go through a 1/4" Plexiglas mounting plate. So, only 1/8" is going into the PS.

I remounted them last night and I can't get them to fail now.

I rewired them (mounted to Plexiglas) this morning to my motor controllers and they've been consistently working!

I'm at a loss to explain this.

They seem to work when they want to and not work when they want to.

I don't think Automation Technologies is letting me return them and exchange them for the unregulated power supply. They just want me to send them back for a replacement.


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## RJSakowski (Feb 19, 2020)

Another thought is a wire whisker from one of your wires shorting out.  Easy enough to do that.  If the problem reoccurs, check resistance with the power off.  In fact I would do that now while everything is working to have a baseline for comparison if when things go south again.


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## Nigel123 (Feb 19, 2020)

It could be that the overvoltage protection is kicking in and shutting down the supply
years ago I had some 15v power supplies do that
Do you have an adjustment sheet for the supply
I used to turn the adjustment pot to zero then slowly increase it desired voltage
If I went too far the power supply would trip and would only power up when the
voltage was lowered and powered down and back up
Not sure if this if the problem but worth checking out


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## devils4ever (Feb 19, 2020)

Yes, there is a pot to control the output voltage. There is an over voltage circuit.

It's possible the over voltage circuit is getting triggered. I'll measure the output voltage tonight.


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## Nigel123 (Feb 19, 2020)

If you can find an adjustment sheet on the supply it should show how to properly adjust the supply
The supplies I worked with you set your max voltage with one pot then set the over voltage pot to trip
if it went higher
These were older power supplies your power supplies might have a different procedure
Hope it helps


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## devils4ever (Feb 19, 2020)

I misspoke. The mounting screws were M4 x 6mm going through a 1/8" aluminum plate.

There are no whiskers that I could see on either unit.

The pot control was able to get the output voltage to about 53V. But, I couldn't get it to fail after numerous tries and various settings.


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## Nigel123 (Feb 19, 2020)

Sounds like its working intermittent problems are hard to trouble shoot 
I would not trust them unless I knew why they are working now
My thing would be exchange them for ones that work off the bat if covered under warranty
If you take a chance you are only out 28 dollars each 
I think I read they would exchange them


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## devils4ever (Feb 24, 2020)

I ordered the unregulated power supply from Automation Tech. I'm done with the switching power supplies.

They seem to be offering me a refund on the switching power supplies, but we'll see. It was a little convoluted transaction.

Gory details (to those who are interested):
I ordered the switching PS via eBay. I initially had trouble with one PS. I send them a message and they told me to return it for an exchange. Then, the other PS starting acting up. I sent them two more message: one saying the second one was intermittent and the other asking for an swap with the unregulated PS (and additional $$$). These two email were ignored. Time passes. eBay sends me a message saying they agreed to a refund. It was unclear if this was for one or both PS. So, I sent back both today. We'll see if I get a refund for one or both or an exchange for the same ones. Over the weekend, I order the unregulated PS from their website. Hopefully, everything will work out!


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## devils4ever (Feb 29, 2020)

Well, I got the new unregulated power supply and installed it. It's a beast.

I'm still waiting for my refund from the switching power supply, but it's supposed to be coming.


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