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  #31  
Old Thu 16 October 2008, 09:37
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Dave, I think you will be okay. Just be sure your transformer is under 35VAC......that will rectify to under 50VDC to be within the Gecko 540's limit.
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  #32  
Old Thu 23 October 2008, 19:01
dragonfinder1
Just call me: Dave #49
 
Astoria, Oregon
United States of America
A quick email to GeckoDrives about the G-540 brought a reponse that said baisicly, add a 3.5k resistor for the currect limit and I should have about 87.5% of rated torque.

Dave
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  #33  
Old Mon 08 December 2008, 05:42
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
G-540 Pics

I would love to see pictures of your control box. Been reading the Power and Torque threads and the G540 looks intersting.

The Control system clicked this morning in my head. It was a mess of boxes and wires and after reading for 20 plus hours on the Forum (Thanks Gerald!!!) Today I reviewed a picture of a control box and all the wires and controls make sense to me now. It is not a lot of wires, but a few wires 4 times (or 5 for those wiring 5 axis stuff)

Gerald how well is the higher voltage (What voltage are you actually at now) holding up for you?

Also if you are running at 180 degrees what is the max temp to safely run the 7.2 motors? (I hope that has not already been asked ) See I do my home work
http://www.mechmate.com/forums/showt...ght=Motor+Heat
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  #34  
Old Mon 08 December 2008, 05:53
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
We measure about 45VDC and it is all cool enough.
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  #35  
Old Sat 20 December 2008, 10:24
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Power Supply PS-8N50R5R12

Working on the Control Box.

Ok I am filtering this power thing through my head.

Man I am glad I had BEE (Basic Electricity and Electronics) and component level training in the Navy !!! This stuff makes my head hurt.

Easy stuff.....

Motors PK296A2A-SG7.2 (Ordered)

Gecko 203V Drives

PMDX-122 Bob.

Still looking for good deals on ......

Control Box and Backboard
Internal Controls and Relays

Head on fire and brain melting on......

POWER SUPPLY

http://www.antekinc.com/PS-8N50R.pdf

I plan on having growth for indexer and wanted to be able to just add the next Axis (I know all channels of the PMDX-122 are used). I will leave enough space to get to different BOB or stack and add a second PP to drive the remaining AXIS. (2 Parallel ports and 2 Bobs should drive 8 203V's)

My big question was in taking the standard approach for Half-Coil using the "standard " Motor, I want to take Gerald's approach (as I agree ) to not reduce the voltage by .66 . I want to be able to supply the upper limit that he has provided at 48VDC going into the Gecko's. Since they max at 7A and 80v this should not be an issue.

My concern is the PS-8N50R5R12 is at 50VDC (I picked the 8N for axis growth) . With half coil wiring will this be an issue. All of the Oriental Motor Specs I saw have the Half Coil voltage at 24 VDC

http://www.mechmate.com/forums/showthread.php?t=1114 post 2 shows Bipolar wiring.

http://www.orientalmotor.com/product...XTA/StPk29.pdf (page c-232) show all Half-Coil wiring at 24 volts.

Soooooooo ..... That being said my head is smoking. I understand you reduce voltage and increase current to get to the same power. P=IxE (ohm's law) but what I see in these threads we are changing the wiring but the voltage is still at least 35V. I read for Bipolar (Full coil?) the motors are rated for 48VDC and Unipolar(Half coil) they are rated at 24.

http://www.orientalmotor.com/product...TA/StIntro.pdf
(good reading on OM and motors)


All this said and done are we not just building this box?

http://campbelldesigns.net/enclosure.php
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  #36  
Old Sat 20 December 2008, 12:21
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The voltages mentioned in the OM specs are not relevant - they do not use Geckodrives.

A good voltage to supply to the Gecko's, for half-coil(unipolar) wired PK296A2A-SG7.2 motors, is 40VDC. See this thread for the most suitable Antek supply: Which Antek power supply for 4x PK296B2A-SG7.2, 4x G203V, PMDX-122 and 110VAC at home

5 motors will happily run off a 400VA supply.

Yes, you can buy a ready-made box from Bob Campbell. I don't think it provides for e-stopping the router/spindle. It breathes external air and you need to do filter maintenance.
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  #37  
Old Sat 20 December 2008, 12:42
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
PMDX-122 and gecko's

Correcting my Axis coments above. Geral had a nice summary in post 12

Here.

http://www.mechmate.com/forums/showthread.php?t=1023

PMDX-122 and 5 203V. will work.
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  #38  
Old Sat 20 December 2008, 12:43
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Ready Made Box

I saw all the holes in that unit and I would not be learning as much as I am here if I did that .
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  #39  
Old Sat 20 December 2008, 12:47
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
40 Vdc

Yea I have read about the 40 VDC, but you are pushing your system a little more and driving it at 48 VDC correct?

What PS are you driving that with?

I agree with you about giving the motors enough room to perform because it is unlikely that you will run all 4 motors at slow speed at the same time. Some will be in some state of holding while the others are turning.... or is my thinkning wrong there?
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  #40  
Old Sat 20 December 2008, 13:04
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Our power supplies are non-Antek. Did test the motors at 48V in winter and they were okay. Our current power supplies have measured out at 45V, and here in summer now, the motor heat is okay.

There is a popular misconception that motors draw their peak power at low speed. Having measured the real thing, the motors draw peak power at high speed with high load. All 4 (or 5) motors can't run like that all at the same time.
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  #41  
Old Fri 09 January 2009, 06:37
Nikonauts
Just call me: Nikonauts
 
Johore
Malaysia
I'm planning to build my own PSU.

wonder what dictates the Amp rating of a transformer?

One determine the voltage output of a transformer by the amount of winding, but what says how much max amperage it could deliver? (except for the bridge and capacitor with each has it's own rating). the wire gauge?
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  #42  
Old Fri 09 January 2009, 07:44
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
I'm no transformer or winding expert, but it will be a combination of factors. The limiting issue is I believe, heat dissipation.

You certainly need sufficient gauge wire, or you'll burn out the wire from heat. I suppose you could do something impractical like immerse it in liquid nitrogen to pull a few more amps out without a meltdown, but that's useless speculation.

Next, you need to insure that the insulation around that wire is stable at your operating temperatures. If you get enough heating during operation to melt the insulation, then the winding shorts, you get more heat, and eventually the wire fails.

It seems to me that the size of the transformer core may influence the range of amperages that can be handled efficiently (I.E. without producing excessive heat), but I'm out of my depth once we talk magnetics.

I know that creating a "magnetic short circuit", for example by using a U shaped bracket and a through bolt with a toroidal transformer is a bad thing to do, but I'm not sure what the failure mode is, which is to say what element of the system regulates the ultimate amount of current flow. It certainly won't work to produce output voltage, but I don't know what element is going to heat up and become unhappy.
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  #43  
Old Fri 09 January 2009, 07:44
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Yes, the wire gauge and the mass of the ferrite ring core.
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  #44  
Old Fri 09 January 2009, 08:48
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
And TYPE of core material, which influences the flux density of the core, and core type (toroid or E-I Lamination) will also be a factor.
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  #45  
Old Fri 09 January 2009, 10:13
Nikonauts
Just call me: Nikonauts
 
Johore
Malaysia
thanks guys, i guess i just have to delve deeper. hopefully i'll come back informed and able to share. normally i hate anything EM, but for our application i think i'll get away without having to deal with anything too hardcore.
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  #46  
Old Fri 09 January 2009, 11:34
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
I ended up with the ANtek PS-4N48R12 - Not listed on their site.
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  #47  
Old Tue 13 January 2009, 07:12
Nikonauts
Just call me: Nikonauts
 
Johore
Malaysia
I found a transformer with winding that's just nice for G540.
It step down from 220V or 240V to 36V.
Worrying about spike or noise or instable voltage, i soldered my wire to 240V input connector. So if the real source voltage is 220 i'd get a little bit below 36V.
Measured the voltage after the bridge, giving me me around 34.5V.
After fitting in a condensor 15000uF, it gives a very nice 49V.

I'm still looking for ways to make sure voltage doesn't go over 50V. things like a fuse for voltage. is there such a thing?

beware though, when wiring the bridge rectifier make sure you test the conductivity between each combination of any two legs. luckily a friend was there with me and suggest that i do the test first. only two legs were marked, one marked +DC the other AC. It happens that the connection is like an X. Confused with my english?
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  #48  
Old Tue 13 January 2009, 07:56
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Square full bridge rectifiers are always "X" connected.
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  #49  
Old Wed 04 February 2009, 13:28
javeria
Just call me: Irfan #33
 
Bangalore
India
Hi G' - I have a old transformer from a akai vcr which gives me like 20 volts +- 1v

my input voltage on the AC mains is usually 180 to 200 during the day and at night arount 195 to 210

the 20V(DC voltage) was measured during the day.

Now I am planning to use the same transformer for the 24v relays -

I know that most of my proximity switches - ssr's etc will work with this voltage

I was worried if there will be any reliability issues with the mechanical relays due to a lower voltage.

I need your help here.

RGDS
IRfan
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  #50  
Old Wed 04 February 2009, 13:49
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Irfan,
What does the datasheet for the relay tell you about coil dropout? There is usually some range of voltage that will work for energizing the coil.
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  #51  
Old Wed 04 February 2009, 18:09
LIBBIT
Just call me: John
 
Mt Roskill, Auckland
New Zealand
Hi,

I've read all the discussion about sizing the transformer etc etc....

I also have to apologise if I've missed something but....the MotionKing is a 8 wire motor and the Gecko G201V drive cant do Unipolar so how do i connect the motor? I must say that I have a 3.2:1 self designed T5 timming Belt gearbox so I'm looking for reves more than torque!

Regards

John
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  #52  
Old Wed 04 February 2009, 19:37
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Irfan, I wouldn't mess with low voltages on mechanical relays. As Heath says, the datasheet will give the theoretical answers, but a chattering relay is not pretty.
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  #53  
Old Wed 04 February 2009, 19:42
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by LIBBIT View Post
. . . . the Gecko G201V drive cant do Unipolar
Says who?

There is some confusion over the true meaning of "unipolar", which is often used interchanged for "half-coil".

The type of "unipolar" we are talking about for the 8-wire MotionKing, is half-coil, and that is happily done by G201, G202 or G203V drives. (There is no G201V)
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  #54  
Old Mon 09 February 2009, 22:04
LIBBIT
Just call me: John
 
Mt Roskill, Auckland
New Zealand
Tks for that. I did see this quote. Sorry the G201V was a type-O. It was note#25 by Richards on Wed 27 Aug 2008,23:16. I'm mechanical so this electrical stuff is the biggest challenge fo rme. So it will be safe to order the MotionKing 34HS9801?
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  #55  
Old Mon 09 February 2009, 22:34
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Richards View Post
. . . . . A six-wire motor can be wired either Bipolar series or half-coil when used with a Gecko stepper driver. It cannot be wired Unipolar. The Gecko stepper driver does not have that option. . . . .
Mike, would you agree that there is confusion about using the term "unipolar", which is often used instead of half-coil?

John, it will be safe to order the MotionKing 34HS9801 motors to use with geckodrives G201, G202 or G203V.
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  #56  
Old Tue 10 February 2009, 03:21
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Gerald,

Yes, there is a lot of confusion about the terms, Unipolar, Half-Coil, Bipolar Parallel, and Bipolar Series - and a new term that I'm adding today - Bipolar Half-Coil. I've added to the confusion by using those terms very loosely. The term Unipolar, although referring to the way the stepper is driven, also is the term most motor manufacturers use when giving out electrical specifications for a motor. On the Oriental Motor web site, six lead motors have two specifications, Unipolar and Bipolar Series. Eight lead motors have an additional specification, Bipolar Parallel. Each electrical specification has a Holding Torque specification, an Amp specification, an Inductance specification and a Voltage specification. The 32 X SQRT(Inductance) = MAX voltage formula from Mariss at Geckodrive makes the manufacturer's Voltage specification obsolete. Those specifications are very important when selecting a power supply and current limiting resistors on a Geckodrive based system.

Use the Unipolar electrical specifications when using the Half-Coil method of physically connecting the motor to the stepper driver.

When used in a technical sense, the term Unipolar is really a description of how a stepper motor is driven by a Unipolar stepper motor driver. In the same way, the term Bipolar is also a description of how a stepper motor is driven by a Bipolar stepper motor driver. (Right now, as I'm writing this, I have an Oriental Motor CSD2120-T Unipolor stepper driver sitting on my desk next to a Geckodrive G203v Bipolar stepper driver. The CSD2120-T Unipolar driver is vastly inferior in performance when compared to the superior G203v Bipolar driver.)

ALL GECKODRIVE STEPPER DRIVERS ARE BIPOLAR DRIVERS. Of course that means that there are only four motor connections on a Bipolar drive. The user has to decide how he is going to use the motor and then wire the motor appropriately.

That's where the fun begins. A six wire motor can be connected to a Geckodrive by either using a Bipolar Series connection or by using a Bipolar Half-Coil connection. See, I've just added to the confusion by making up a new term, Bipolar Half-Coil, but the term Bipolar Half-Coil more accurately describes both the physical connection to the stepper driver and the method the stepper driver uses to drive the stepper motor.

I wouldn't normally use Bipolar Series connections (except on the test bench when I'm just playing with motors and drivers). Here's why:

- A Bipolar Series connection has 40% MORE holding torque than a Bipolar Half-Coil connection.

- A Bipolar Series connection requires 30% LESS current (Amps) than a Bipolar Half-Coil connection.

- A Bipolar Series connection has 4X MORE inductance than a Bipolar Half-Coil connection.

The inductance specification is the killer. A Bipolar Series connected motor will have very poor performance at high speeds when compared to either a Bipolar Half-Coil connected motor or a Bipolar Parallel connected motor. Some stepper motor applications require high torque at low speeds. For those applications, a Bipolar Series connection is ideal.

I wouldn't normally use Bipolar Parallel connections either. Here's why:

- A Bipolar Parallel connection has 40% MORE holding torque than a Bipolar Half-Coil connection.

- A Bipolar Parallel connection requires 40% MORE current (Amps) than a Bipolar Half-Coil connection.

- A Bipolar Parallel connection has the SAME inductance as a Bipolar Half-Coil connection.

Here, the current specification is the killer. High current means high heat. Lots and lots and lots of heat when the stepper motor is driven at its MAXIMUM voltage. There is really no benefit of wiring an eight-lead motor using Bipolar Parallel connection and then de-rating the voltage or limiting the current. You would end up with the performance closer to Bipolar Half-Coil than to Bipolar Parallel.

I have a bunch of stepper motors on shelves and in drawers - over twenty-five at the latest count, most of which were taken out of obsolete control boxes that I built to control Kodak Series-S photo printers. All except one are six-lead motors. The one exception is an Oriental Motor PK299-F4.5A. It is my "go to" motor when I need maximum performance regardless of the heat. In the future, whenever I need an ungeared stepper motor, I will probably always buy the PK299-F4.5A motor or its little brother, the PK296-F4.5A, but I will wire it Bipolar Half-Coil. That would leave open the option of changing the wiring to Bipolar Parallel if I ever needed 40% more torque and if I had a way of dealing with the heat or I could change the wiring to Bipolar Series if I just needed high torque at low speeds.

So, in summary:

- All Geckodrive stepper drivers are Bipolar stepper drivers.

- When I use the term Unipolar in conjunction with Gecko products, I'm referring to the electrical specifications of the motor - not to the method of driving the motor.

- I use Bipolar Half-Coil connections unless the application would benefit more from Bipolar Series wiring or Bipolar Parallel wiring.

- I use either belt-drive transmissions or gear boxes to get the most Power out of a motor, where Power = Speed X Torque. The added benefit of a geared motor is getting better resolution.

To those who have already wired up their motors using either Bipolar Series or Bipolar Parallel: Don't worry about my opinions. All three wiring methods work. All three wiring methods will give excellent results. All three wiring methods are 100% acceptable - according to your particular needs.

Last edited by Richards; Tue 10 February 2009 at 03:34..
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  #57  
Old Tue 10 February 2009, 16:35
LIBBIT
Just call me: John
 
Mt Roskill, Auckland
New Zealand
G,

Again thank you. I'm still busy getting prices, damm the stuff is expencive here in NZ, when i have a complete picture in my head i will post a summary in the forum for comment. I just need to say old Rick at Superior bearing is a very help full chap.

John.
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  #58  
Old Sun 15 February 2009, 21:02
kanankeban
Just call me: Hector #89
 
Monterrey
Mexico
Quote:
Originally Posted by bradm View Post
Dave, I'm running a G540 with OM motors and a 7.2 geardown, and I'm happy. So it looks to me like your reasoning is sound.
Hi,
could you comment on your setup, what power supply are you using and do you have proximity sensors in your configuration? I was thinking in getting on of those 540īs
Thanks...
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  #59  
Old Mon 16 February 2009, 13:15
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Hector, I homebrewed my power supply from parts I had lying around; I had an existing 70v 300va toroidal transformer, but it has an input option for 120 or 240v primary. I wired the 240v primary to my 120v source and thus it's now a 35vac transformer.

Add a 25a bridge on a heatsink, and a big cap (can't recall the spec right now), and I was good to go.

I do have proximity sensors. The G540 has several optoisolated inputs that are just perfect; essentially you use the proxies to pull them down to ground. Since I ended up with 3 wire proxies instead of 2 wire proxies, I have a small auxilliary 12v supply for them.
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  #60  
Old Mon 16 February 2009, 14:01
kanankeban
Just call me: Hector #89
 
Monterrey
Mexico
So could you recomend going with a 540 instead of going with the pmdx-122 & 203V conventional formula...what are the things one would be not getting if chossing the 540 instead? The 540 looks like a reasonable choice the 203V seems like overkill...
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