Newbie- Please help me choose stepper driver

[eddie3000]

Yes, I made the mistake of buying a chinese driver on ebay last september-october. Pathetic! My bad!
I am now going to buy a better driver for my motors. The motors are rated at 2.8A, 3.6mH and 1.4 ohms. I guess they need anything between 40-60V to perform adequately. Am I wrong about this?
I quite like the G540 and the price tag. It's conveniently all in one box, but max. voltage is 50V. The nice people at Geckodrive recommended me not to go over 51-52V. Absolute max. is 64V, but they absolutely do not recomend going anywhere near that point.
If I want a more powerful drive, I have to go to a G20x. These are a slightly more expensive option, and aren't as neat. And, if I power them with the max. voltage they could handle I think I could burn the motors. I will also need a breakboard (or whatever you call 'em).
My main question is, would a g540 be adequate for driving my motors, or would a more powerful one be best? Has anybody got a g540 with motors similar to mine? If I only use three axis on a g540, can I have the fourth with nothing connected to it? Would it get damaged?
I've also seen other brands on kelinginc.net, some "digital" step motor drivers others have kindly pointed out to me in this forum. Most people around here seem to like Geckodrives.

[Richards]

I've used many motors with the G540 that should have been used with a G203v or other 'high powered' Gecko drive. I limited the voltage to 48VDC. I limited the current to 3A (although I could have gone as high as 3.5A). Then I ran the motors to see how well they performed. Most of them worked very well for the application that I needed - CNC router. In that application, high speeds are not necessary - even when the motors are geared down 3:1. For instance, with a rack and pinion drive having a 1.25" diameter pinion gear and 3:1 gear reduction (via a belt-drive), 750 RPM gives me 16" per second, which is more speed than I can use in that application.

Oriental Motors PK296B2A-SG3.6, PK296-F4.5A, PK299-02AA and PK299-F4.5A have all been with the G540. All worked well after I 'crippled' them by limiting their voltage and current to fit within the boundaries of the G540.

I've also used those drives with a G203v. Again, for my application, either the G540 or the G203v would have given adequate performance. The G203v required the use of a PMDX-122 break-out-board. The G540 was used right out of the box.

For those applications that are price sensitive, if a G540 can drive the motor fast enough with enough torque to do the job, you've found a solution. If you need more speed or more torque (assuming that the motor had to be 'de-rated' when used the the G540), you always have the option to replace the G540 with some G201x or G203v stepper drivers and a break-out-board.

[Mariss Freimanis]

eddie 3000,

Eddie, let me add to Richard's excellent post. I'll start by going over what's involved when you say you want your motors to perform adequately:

1) Power supply voltage has no effect on low speed torque. This is the torque you get at most feed-rate speeds where your mechanism is doing actual work.

2) Power supply voltage affects how much torque you have available at high speeds. These normally are the rapid speeds where the motor is under little load while repositioning the mechanism.

3) A law of nature is every advantage comes at a price. With step motors, increasing voltage brings increasing performance at the cost of increasing motor heat. Nature unfortunately fixes it so that the heat increase outraces performance gain.

Your motor's maximum supply voltage is set by the equation Vsupply = 32 * SQRT (3.6 mH) or 60VDC. By "maximum" this equation means 60VDC will bring the motor temperature up to 85C, the motor's maximum rating. 85C is hotter than McDonald's coffee.:-)

60VDC will happily spin your motor up past 3,000 RPM. It is a complete waste if your application never sees speeds higher than 1,000 RPM. It is important to differentiate between maximum permissible supply voltage and optimal supply voltage. Maximum permissible means the motor will be heat stressed but undamaged while optimal means the motor will meet all your requirements without any unnecessary capability beyond a safe performance margin.

Mariss

[eddie3000]

Thankyou very very much for your replies. I apologise for the my very late answer. Being busy isn't an excuse.

I have finally opted for the g540 with a 48V power supply. I think it will be adequate for what I need. After all, I'm just a hobbyist.


I would like to wish everybody on this forum a Merry Christmas and a Happy New Year.