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  #1  
Old Thu 27 November 2008, 18:53
BHawthorne
Just call me: Brad
 
Wichita, KS
United States of America
Copied from his personal thread:

So far I have my PMDX-122, 4 G203V and 4 PK296B2A-SG7.2. I would like to be able to plug this system into regular US 110V home power. With that in mind, what Antek power supply should I order?
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  #2  
Old Thu 27 November 2008, 22:51
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
This question needed a thread of its own because that choice of motors/drives/pmdx has become "standard" and because Mike & I have recently done some tests on that motor's heating, as well as the actual current drawn from the power supply.

We could have 3 different consumers from that power supply:
1. The 4 G203V's driving the 4 motors (to be calculated below)
2. The PMDX-122 (7-12VDC or 6-9 VAC)
3. Proximity switches (12VDC)

Calculating the voltage for the motors: See Calculate the Voltage and VA size of the DC power supply for stepper motors/geckos which basically says "Find the inductance of the motor from its specsheet in milliHenry, take the square root of the mH value and multiply that by 32. For example, a motor that is rated 1.5mH needs: 32 x √1.5 = 39 Volt" That PK296B2A-SG7.2 motor, when wired half-coil (unipolar) is 1.5mH and so the calculated 39V is correct for it. Antek supplies are available at 38V and that would be my voltage choice if buying from Antek. (On our machines, we now run at 40V without problems in our summer link)

Antek supplies are bulky animals - there are good reasons to avoid buying too big. I know that 300VA is sufficient for 4 motors (link), and I see that their smallest 38V supply is 400VA. So, off Antek's web page, I would pick the PS-4N38

But that will only drive the geckos and the motors, and not give the few milliamps at the special voltages for the PMDX and proximities. For that you will have to ask Antek to give you a 12VDC output as well (12VDC being suitable for both the proximity switches and the PMDX). Suggest you ask for 1 Amp at 12V, making 12VA, on the second output - that is plenty enough for the PMDX and the prox. switches (plus relays).

So, the full buying spec to Antek will be:
Input: 110VAC
Output1: 38VDC 380VA
Output2: 12VDC 12VA
Total VA: 392 (PS-4N38 with second 12VDC 1amp output)

Mike, would you be comfortable with the above selection?

(Personally, I wouldn't buy the ready made Antek. It is too bulky for my liking and I don't like the small terminals for connecting the output wires to the Geckos. It is supposed to be a safe choice for somebody who doesn't want to risk building their own supply and make smoke - but we have heard of one Antek that was shipped without testing and made smoke at the client's table.)
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  #3  
Old Fri 28 November 2008, 05:57
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Gerald,

I agree with your selection, including voltage and amperage. On all of my tests, I've never had the power supply heat up when I used a toroidal transformer. (A standard "square" transformer always ran hot - too hot to touch, even when the motors were lightly loaded.)

I also agree with your statement about the bulk of the Antek. All anyone really needs is the proper toroidal transformer, a bridge rectifier and a suitable capacitor; however, finding adequately sized capacitors with screw terminals is becoming more and more difficult, since most designers have switched to the "snap-caps" that are generally soldered onto a circuit board. (I recall seeing some photos of snap-caps being hot glued to a thin piece of MDF. That would work although I would prefer drilling holes through the MDF and securing the snap-caps with nylon ties.)

The formula used to determine the amount of capacitance needed is: (80,000 X Amps) / Voltage. So, (80,000 X 12A) / 39 = 24,615 uF, although in practical use a 15,000 uF capacitor would normally be adequate since it would be improbable that all the motors would be drawing maximum current at the same time.
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  #4  
Old Fri 28 November 2008, 07:21
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Thanks Mike

I forgot to recalculate the capacitors when changed my motors from 75V/2A to 40V/3A recently and stayed with 10000uF capacitors, which theoretically are too low. But, all seems okay. So I agree that 15000uF capacitors would be adequate.

When I started this forum, I was very wary of telling people to build their own power supplies, because of safety and liability issues. However, I am having a change of heart on this. Buying a ready-built supply is no guarantee that it is any safer than one you can build yourself - except that you can try and sue the supplier when things go wrong. When folk signed up at this site, they agreed they won't sue me, so I am going to take a bolder approach.
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  #5  
Old Fri 28 November 2008, 09:48
BHawthorne
Just call me: Brad
 
Wichita, KS
United States of America
My reason for mentioning Antek is that I'm pretty ignorant about electrical wiring and am seeking the most simple bolt-on setup I can find. The less I have to build of the electrical side of things the safer I feel about the build. If Antek isn't the ideal answer, would one of the other MechMate builders be able to build something I could use for the power supply to better match the equipment? I'd prefer gettign something I just have to mount to the Hoffman case and wire per instructions. I'm pretty igorant about electrical but I'd like to think I could follow exact instructions to put it together if they're clear. I'm not looking to get lost in all the electrical math. I'd just like to order something and install it in a case.

I'd be happy to see a simple parts list for the Hoffman case contents and that way people can go and buy their 4 G203V's, PMDX-122, proximity switches and whatever else is needed and just put it together as the instructions state without experimentation. My goal is to buy everything else I need to complete the table top test in short order. Today I'm looking around town for a suitable Hoffman-like enclosure.

Last edited by BHawthorne; Fri 28 November 2008 at 10:18..
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  #6  
Old Fri 28 November 2008, 10:12
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Brad,
We can help with some instructions. Just let us know what you need for a voltage and the rest isnt so bad.
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  #7  
Old Fri 28 November 2008, 10:47
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Brad, lots of people are happily using Antek supplies, and there isn't anything inherently wrong with them that is going to affect the performance of your MM. It is a pity that Antek is the only company to offer an affordable ready-built supply, because with some attention to small details, it could be done better, without adding significantly to the expense.

Absolutely nothing against you if you do go for the Antek. Just be cautious of:
1. The size (link) in relation to your cabinet
2. Connecting the 4 Geckos to the single terminal on the Antek
3. The fact that you may be the first person to switch it on.
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  #8  
Old Fri 28 November 2008, 11:12
BHawthorne
Just call me: Brad
 
Wichita, KS
United States of America
I take it the larger the enclosure the better everything will fit in. I think I'll go with the Antek and document the build in detail, so anyone else like me can just read about my table top test build and just build it step by step.
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  #9  
Old Sun 30 November 2008, 22:41
BHawthorne
Just call me: Brad
 
Wichita, KS
United States of America
Got an email today from Antek:

Quote:
Hi,
We can not get the 12V from this model. Can you use the PS-4N42R12 instead?
What is your application?
John

--- On Fri, 11/28/08, wrote:

Subject: Price quote for power supply
Date: Friday, November 28, 2008, 12:59 PM


I'd like to get a price quote for a power supply:

Input: 110VAC
Output1: 38VDC 380VA
Output2: 12VDC 12VA
Total VA: 392 (PS-4N38 with second 12VDC 1amp output)
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  #10  
Old Mon 01 December 2008, 00:54
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
That PS-4N42R12 is not listed on their web page, but it seems to be:

Input: 110VAC
Output1: 42VDC 400VA
Output2: 12VDC 1Amp regulated or 2A un-regulated
Total VA: around 400

I would use it. The 42V is maybe a bit high (over the 39V calculated), but I have tested at 48V and it was okay during that test. If you think the motors are too hot for your liking, you can adjust the current on the geckos.
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  #11  
Old Mon 01 December 2008, 07:31
jhiggins7
Just call me: John #26
 
Hebron, Ohio
United States of America
Gerald and Brad,

I am considering adding an independent Toroidal Transformer to the Control Box for the 9 VAC needed for the PMDX 122.

It appears that Hennie, http://www.mechmate.com/forums/showt...5&postcount=37 and Linus http://www.mechmate.com/forums/showt...3&postcount=21, among others, have taken this approach.

As an example the AN 0109 http://www.antekinc.com/AN-01xx.pdf, adds only $10 to your Antek order and weights .5 lbs.

So Brad you could order the PS-4N38 to power the GECKO's/Steppers and add the AN 0109 for the PMDX 122. As an added benefit, the AN 0109 has an extra secondary for any future expansion that may be needed.

The AN 0109 could be powered in parallel with the PS-4N38 and since it is independent, the AN 0109 could be placed in a location of your choosing in the Control Box.

Just another option for your consideration. Hope this helps.

Regards,
John

Last edited by jhiggins7; Mon 01 December 2008 at 07:45..
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  #12  
Old Mon 01 December 2008, 08:12
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
John, the reason that Hennie & Linus have the second smaller transformer is because it is supplied with their bob's. I agree that a second small transformer is a quick way of powering a PMDX, but it doesn't answer the possible need to power proximity switches.

Adding your own winding to the big toroid is also dead easy. Power supply for the PMDX-122 Parallel breakout board - 9V AC from main transformer

Anyway, Brad is the type of guy who would rather not buy loose transformers.
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  #13  
Old Mon 01 December 2008, 09:11
jhiggins7
Just call me: John #26
 
Hebron, Ohio
United States of America
Gerald,

Thanks for the clarification about the source of Hennie and Linus's transformers.

If more low-voltage power than can be supplied by the PMDX, J8, Pin1, Aux +5 volts is needed, I plan to build a low voltage DC power suppply using the extra secondary of the AN 0109. Of course, I realize that Brad is looking for a pre-built power supply so this option may not be attractive to him.

As for a few turns around the main toroidal transformer to supply ~9 VAC to the PMDX 122(I had seen the referenced thread before), I'm afraid I would consider that a kludge in an otherwise elegant design. I haven't seen any pictures of such a set-up, but besides being somewhat unsightly, I would worry that unless very well secured, the voltage supplied could vary wildly and potentially introduce intermittant problems. Just my opinion...

I think the MechMate Forum is fantastic. So, don't take my comments as anything other than constructive criticism of ideas.

Regards,
John
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  #14  
Old Mon 01 December 2008, 09:32
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
John, it is not a kludge at all - that is the way in which transformer builders add extra secondary coils. The output voltage is as steady as a factory-built version. See also: Build your own toroid transformer from a partial kit . . . .
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  #15  
Old Mon 01 December 2008, 09:33
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
John,
I have wound my own toroidal power transformers and inductors and you will not have the problems you think. Once the additional secondary winding is added, you can secure the wire with electrical tape. We typically use mylar tape in the industry but any good tape ( mylar, electrical, capton, just dont use masking tape or fabric style tapes) will work. Several MM guys have done this already with good results even though they are not electrical types. Good luck with what you choose.
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  #16  
Old Mon 01 December 2008, 09:48
jhiggins7
Just call me: John #26
 
Hebron, Ohio
United States of America
Thanks Gerald and Heath.

I stand corrected!

Does anyone have any pictures?

Regards,
John
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  #17  
Old Mon 01 December 2008, 11:11
BHawthorne
Just call me: Brad
 
Wichita, KS
United States of America
My interest is to merely have something I could attach to the Hoffman case, wire to the 110 US and to the 4 G203V and the PMDX-122 without introducing unknown factors like building power supplies. I think it would be good for both Antek and MechMate to come up with something that would just work properly by just wiring it in. If something could be worked out on this, it would make this step a lot easier for builders like me.
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  #18  
Old Mon 01 December 2008, 11:17
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Brad, we did try a special MechMate version with John Ango at Antek, but he couldn't make deliveries. Smaller Readybuilt power supplies from Antek - good idea, but delivery disappoints
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