DOes this look like a promising stepper driver?

[phantomcow2]

http://www.bright.net/~agarb/STMD/AVR_STMD.html

65 dollars for a kit to solder yourself. I am looking to drive some 2.8A bipolar steppers, looks like this fits the specs. I was wondering if some of the more knowledgeable folks could comment on this drive.

I was also considering
http://www.motioncontrolproducts.com/MSD542.html
This is a good price, looks like a nice driver also. My concern is that if something goes wrong, it will be difficult to service. Being all enclosed, I dont know if it is possible for me to do repairs, or I have to ship it back to england. I like that with the kits, you know exactly what is going on. Kind of like how Sieg machines are, you have to tear it down to clean it, but know exactly how it works and where to look for problems.

[mcpltd]

Is is only a metal top to the driver, two screws and you will see the main board.
Also out of the 3000 drives we have sold within the last 6 months we have only had about 10 drivers fail, and some of the failures were user error.

Originally Posted by phantomcow2 http://www.bright.net/~agarb/STMD/AVR_STMD.html 65 dollars for a kit to solder yourself. I am looking to drive some 2.8A bipolar steppers, looks like this fits the specs. I was wondering if some of the more knowledgeable folks could comment on this drive. I was also considering http://www.motioncontrolproducts.com/MSD542.html This is a good price, looks like a nice driver also. My concern is that if something goes wrong, it will be difficult to service. Being all enclosed, I dont know if it is possible for me to do repairs, or I have to ship it back to england. I like that with the kits, you know exactly what is going on. Kind of like how Sieg machines are, you have to tear it down to clean it, but know exactly how it works and where to look for problems.

[phantomcow2]

Excellent, thanks. Do you recommend external heatsinking at certain amperage ratings?

[jeffs555]

mcpltd,
I followed the link to your drives and looked at the spec sheets. They look nice, but I am a little confused about the current rating. Your drives specify a peak current and an RMS current. Most stepper motors specify only one current and don't say if it is peak or RMS, but I always assumed it was RMS. If I had a stepper motor that specified 3.5 amps and wanted to drive it to its full capacity, would I set your drive to 3.5 amps peak, or 3.5 amps RMS?

Jeff

[pminmo]

Most motors have a dc current rating of the coil. A 3.5A motor would pull 3.5A if connected to a DC supply at the coil voltage rating.

It's the same games that S__e__a__r__s played with their motor raings on table saw. The 542 referred too is a 3A driver per phase in relation to other drivers.

[mcpltd]

From my experience most drive manufactures rate their drivers from the Peak current not the RMS.
I have even spoke to the engineers at IMS and a few other driver manufactures and they all came to the same conclusion; that manufactures that dont mention RMS or Peak are all rating their drivers to peak.
Even the Gecko drivers are rated Peak not RMS, so if you are running with the G210 you will only get 4.95A RMS from them.

This is the same for all drivers that i know of apart from some JVL drivers.

Motor manufacture on the other hand do the opposite so you will need to bear this in mind.

Originally Posted by pminmo Most motors have a dc current rating of the coil. A 3.5A motor would pull 3.5A if connected to a DC supply at the coil voltage rating. It's the same games that S__e__a__r__s played with their motor raings on table saw. The 542 referred too is a 3A driver per phase in relation to other drivers.

[mcpltd]

If you wanted to get the full capability from the motor, then you will need to look for a driver that gives you 3.5A RMS.

Originally Posted by jeffs555 mcpltd, I followed the link to your drives and looked at the spec sheets. They look nice, but I am a little confused about the current rating. Your drives specify a peak current and an RMS current. Most stepper motors specify only one current and don't say if it is peak or RMS, but I always assumed it was RMS. If I had a stepper motor that specified 3.5 amps and wanted to drive it to its full capacity, would I set your drive to 3.5 amps peak, or 3.5 amps RMS? Jeff

[pminmo]

Originally Posted by mcpltd From my experience most drive manufactures rate their drivers from the Peak current not the RMS. I have even spoke to the engineers at IMS and a few other driver manufactures and they all came to the same conclusion; that manufactures that dont mention RMS or Peak are all rating their drivers to peak. Motor manufacture on the other hand do the opposite so you will need to bear this in mind.

If your peak rating is SO important, why do you show the RMS rating in your current setting chart? Why not just have them set their 3A motor to your peak rating table..... No real need to answer, because your know as well as IMS that the motor current max is what you would set your drive to get the maximum performance. So what is the point of your showing peak rating if it isn't to play sales games?

[mcpltd]

Its not a sales gimick, we just show Peak and RMS.
The driver is rated as peak just like all the other drivers on the market,
MSD 542 (50V, 4.2A Peak)
nothing is different, apart from we mention it in the manual.

Originally Posted by pminmo If your peak rating is SO important, why do you show the RMS rating in your current setting chart? Why not just have them set their 3A motor to your peak rating table..... No real need to answer, because your know as well as IMS that the motor current max is what you would set your drive to get the maximum performance. So what is the point of your showing peak rating if it isn't to play sales games?

[ger21]

Originally Posted by mcpltd Its not a sales gimick, we just show Peak and RMS. The driver is rated as peak just like all the other drivers on the market, MSD 542 (50V, 4.2A Peak) nothing is different, apart from we mention it in the manual.

The drives most commonly used by hobbiests, the Xylotex, HobbyCNC, and Gecko, are not rated peak, but for continuous operation.

[pminmo]

Originally Posted by mcpltd Its not a sales gimick, we just show Peak and RMS. The driver is rated as peak just like all the other drivers on the market, MSD 542 (50V, 4.2A Peak) nothing is different, apart from we mention it in the manual.

Vexta rates theirs as DC Amps per phase or less
Sure Step rates theirs DC per phase with a Wattage max.
Allegro at DC
National's LMD18245 3A DC
ST rates the L298 at DC but both phases, i.e. 2+2, and also shop non repatative, and a specific repatative duty cycle.
Gecko at DC.
I suspect if these mfg's were to rate theirs at peak, it would be higher.

I can't say what you doing is wrong, but.........

[mcpltd]

Not looked at those drivers apart from the Gecko, but i know that the Gecko is rated peak. It comes down to your definition of DC, and i think if you asked the question to all the manufactures you mention they woulds all answer peak.
try it, ask them and see what they say?

Originally Posted by pminmo Vexta rates theirs as DC Amps per phase or less Sure Step rates theirs DC per phase with a Wattage max. Allegro at DC National's LMD18245 3A DC ST rates the L298 at DC but both phases, i.e. 2+2, and also shop non repatative, and a specific repatative duty cycle. Gecko at DC. I suspect if these mfg's were to rate theirs at peak, it would be higher. I can't say what you doing is wrong, but.........