Hennie, you caught me at a bad time of the morning with these questions - off to Fransch Hoeks's Bastille Day soon . . . .

Do you have spec sheet for the motors? How many lead wires? parallel/series/half-coil options . . . .

That 8 amp integrated power supply you mention; how many volts? Specs?

What drives are you using for your motors? Geckos? Or other? (specs).

Hi Gerald

Will be using Gecko`s 203v
power supply voltage is 100 volts max.
They have 8 wires and the way I look at it inside it is wired the same as per your thread on unipolar /bi polar.So the basic applies.
will mail more specs.

Hennie,

On the www.fullingmotor.com website, I found an FL86ST125-3508A motor that had the same specifications that you listed. Is that the motor that you will be using?

Their website lacked some important information. Because the motors have 8-leads, they can be wired three different ways with Gecko G203v stepper drivers, Bipolar-Parallel, Bipolar-Series, and half-coil. There website does not show which wiring method relates to the specifications that they listed for the motor.

Each wiring method is unique, meaning that wiring a motor Bipolar-Series requires a totally different power supply than if you wired the motor Bipolar-Parallel or half-coil.

As a reference, the Oriental Motor website shows the specifications for its motors according to the way that the motor can be wired. A six-lead motor shows two sets of specifications because a six-lead motor can be wired two ways. An eight-lead motor shows three sets of specifications because an eight-lead motor can be wired three ways.

However, there are some simple formulas that you use to size a power supply to your motors - once you have the specifications for the wiring method that you're going to use.

MAXIMUM VOLTAGE = 32 * SQRT(Inductance)
or
MAXIMUM VOLTAGE = 1000 * SQRT(Inductance / 1000)

The difference between those two methods is how you enter the inductance value into the formula. Given an inductance rating of 7.9mH you could do either of the following:

32 * SQRT(7.9) = 89.94 VOLTS
or
1000 * SQRT(7.9 / 1000) = 88.88 VOLTS

The small voltage difference between the formulas doesn't matter. Also the bridge rectifier drops about 1.5V, but for this type of power supply, I ignore the voltage drop of the bridge rectifier.

In this case, the computed voltage is higher than the maximum voltage allowed by Gecko, which is 80V, so you need a power supply that produces less than 80V. Since the power company may supply slightly different voltage from day to day, it's best to pick 75V as the maximum voltage for a Gecko.

To find the AC rating for a transformer use this formula:

VDC * 0.7 = VAC of the transformer

So, for a 75VDC power supply, you would need a 52.5 VAC transformer. By the way, the more standard 50VAC transformer would give you 70VDC.

To find the VA or current value of the transformer, multiply the current required by each stepper by the number of steppers and then multiply that product by the VAC rating of the transformer:

4 steppers * 3.5A = 14A
14A * 50VAC = 700VA

Some users derate that VA number by about 33%. They would use this formula:

700VA * 0.66 = 462VA

So, bottom line, if I were building a power supply using the specifications that you listed (which may not be right, depending on your wiring method), I would choose a 50VAC 750VA toroidal transformer if I expected heavy use from the motors. If I expected lighter use, I would possibly use a 50VAC 500VA transformer. That would give me 70VDC. I would use at least a 10,000uf capacitor with a working voltage of 100V, but I would prefer 15,000uf to 20,000 uF at 100V. I would select a bridge rectifier rated at 250V or higher and 25A. (Around here, the price between a low power bridge rectifier and a high power bridge rectifier is minimal.)

PLEASE NOTE that the actual voltage that you need and the actual current (Amps) required will depend on how you wire the motors, so you MUST decide on the wiring method and then you must get the proper specifications for the motors from Fulling for that wiring method.

Bon festival Gerald
This is interesting (11h00 – 11h30 Float Procession led by the La Motte Tamboernooitjies, the Congregational Church Brigade and Harley Davidson Main Rd Franschhoek ) Does, Church Brigade and Harley Davidson sound funny together or is it me.
Salut Normand

Normand, that would be quite normal for the quirky village of Fransch Hoek! The parade also had vintage Citroens and Peugots, plus floats from the wine farms showing the enjoyment of wine. :)

Hennie, if I was in your shoes, I would start off with that 300VA 42V transformer that you already have. And then check the transformer for heat in the early days.

Hennie,

I agree with Gerald as long as you wire the motors Bipolar Series, at least to start.

If the motors run cool to the touch and the power supply runs at room temperature, then you might try wiring the motors half-coil.

If the motors still run cool to the touch and the power supply still runs at room temperature then you might try wiring the motors Bipolar Parallel.

Bipolar Series gives the most torque at low speeds when you use a higher voltage, lower current power supply.

Half-coil gives you greater speed at less torque than a motor wired Bipolar Series, but you can only use about 1/2 the voltage of a motor that is wired Bipolar Series.

Bipolar Parallel gives you both high torque and high speed at the expense of high current. It uses the same voltage levels as half-coil, but requires 2X the current.

Thanks for the advice everybody!

Mike that will be the motor ,it comes with a 3:1 gearbox.
Question?
If half coil gives greater speed then the gearbox should make up for the loss in torque?

That gearbox will surely triple the torque.

"Loss in torque" can be misleading. Sure, half-coil gives you less low-speed torque. But at high speeds there is more torque than "full-coil".

Using your existing transformer and wiring the motors series is a no risk experiment. Going half-coil you must carefully watch motor temps. I wouldn't try parallel connections because then your Geckos need to be set at 7Amps and the transformer is just too small for driving 4 motors at 7 amps a piece.

Hennie,

As Gerald said, the 3:1 mechanical gearbox will give you 3 times more torque; however, the gearbox may not be strong enough to actually deliver 3 times the torque. That is the case with the Oriental Motor Pk296A2A-SG3.6 and SG7.2 motors and gearboxes. The 3.6 gearbox is limited to about 350 oz*in (instead of about 1,200 oz in) and the 7.2 gearbox is limited to about 700 oz*in (instead of about 2,400 oz*in).

The motors and gearboxes that you have may be different.

Here is more detailed info on Fulling. (their gearboxes supposedly limited 250kg.cm [3500in.oz], which seems unlikely)

Power supplies
 

Hi Hennie,

For some reason I can`t get to this forum through my normal ISP which is why there has been no response. The 8A limit is imposed by the NTC on our PSU board, we now have 12A and 16A versions. Check our website (www.cncdirect.co.za) for details. I won`t be in SA until the end of the month but please contact Eric (011 882 3372) for a free upgrade to the 12A unit which will be fine for your machine.

The 300VA I sure will also be fine, it is seldom that all the motors are running at full load all the time, the average current consumption of your motors will be around 30% of the full load current and I doubt that the total load will exceed 300VA. Bipolar parrallel connection will offer you the most power from your motors, especially as you have a gearbox they will benefit from the extra speed. Set the drives for 5A and fit 3A fuses. Don`t rely too heavily on the datasheet offered by the manufacturer as you are driving the motor at a completely different voltage, current, switching method, etc. Try them in practice to find the best results.

Regards,
Greg :cool:

This forum is hosted in the USA. There are major SAIX comms problems in SA at the moment.

Thanks all for the help,

I will put it together and play.

Moenie bang wees nie...die boere is mos braaf..probeer is die beste geweer het my oupa altyd gese.

Yes its fine but I dont like fire specially if I started it by being stupid and with my surename ( Helberg ) I might just be one step closer to the big one:)

For those trying to figure out what Kobus said, he is more or less saying don't be timid, be brave and give it a shot. Kobus works for our country's major (sole) electricity generator - they wrote that song "Hello darkness my old friend". Hennie is wise to be cautious! :D

See I AM the brave one. I worked for this company for 20 years. Then went to Europe for 5 years, came back to the country...did 5 years of FLOATING....and now joined my old company to get the lights burning again.;)

Okay, have to admit that we havn't had a power failure for a couple of months now. :)

Kobus you better get sparking ! :)

Hi Hennie

Here is the list of items orderd from RS, its not cheap, but it is the cheapest option for us, these are genuine IGUS chain components. the codes listed are RS part numbers - I dont have the IGUS equivalent numbers at hand at the moment, that info is at home.

2x / 486-8715 Y-car chain @ R334.85 = R669.70
2x / 486-8737 Gantry chain @ R349.41 = R698.82
1x / 486-8793 Y-Car brackets @ R46.72 = R46.72 (pair)
1x / 486-8800 Gantry brackets @ R48.06 = R48.06 (pair)
---------
R 1463.30
VAT R 204.86
----------
Total delivered to my door R 1668.12

These chains come in 1m lengths (22 links ea) so for the Y-car you will have 13 links left over after joining the two as required and the Gantry chain will have 3 links over (note that is for 2750 x 1830 size machine) I may use the left over small chain for the Z-axis to make that look neater - but thats a finer detail.

Thanks Alan

Hennie, here is the parts list comparison between RS and IGUS

486-8715 - 200.03.075.0
486-8737 - 200.05.075.0
486-8793 - 2030.12PZ
486-8800 - 2050.12PZ

its easy to order off their website

Cables
 

Received all my cables today, proxy`s,and connectors
still waiting for a seven pin connector.

With the R/$ exchange rate looking better at this moment you must get those motors NOW !!:)

The thought did cross my mind since yesterday hope the R/$ rate is the same this afternoon.

This question is for Mike Richards

Is Free doors your baby? I have read on a sb thread about this excell program and with Bruce Clark you did this program together. I have downloaded It quite a while ago.
If so Would it work on my MM ( stupid question )Note that I would like to use it but I havn`t mastered importing and exporting files from one program to the other .

In my part of the country I still have a market for mdf doors.

Got some courage to cut the rails
 

Started cutting the rails down. Look at a carpenters method of building a slide to cut down the rails again some off cut material and bobs your uncle.
Kobus made the gadget with the same tape we are talking about put some screws on top just in case it moves.Took me longer to get the hight right then to make it.

Took +/- 15 min to cut through the first rail with one & half disks.The objective is to cut both rails from one side.Had to go home the boss called they wanted to go and watch whales.

Gantry Primed Ready For Rails
 

Primed gantry and spider plate nearly ready for assembly

I hope that yellow grinder is not an Einhell from Trade Centre. They are fine for cutting the rail but grinding the bevel they are not very strong. Nice going Hennie