PDA

View Full Version : Current favourite stepper drivers



GND
04-03-2017, 02:28 PM
I have a couple of potential requirements coming up for stepper drivers, and wondered what were the current favourites within the group. I don't want to overspecify (for cost reasons), but equally don't want to invest hard earned cash on something that will disappoint! Thing is, there are so many random drivers out there, many with uncertain heritage, that it would be so easy to buy rubbish. Hence any thoughts or guidance would be brilliant!

My needs are as follows;

1). Drivers for an existing CNC router, used only for wood cutting, and based on CNC4YOU 4Nm steppers

2). Drivers for a desktop mill conversion, used for precision cutting all metals including steel, and based on 2.2Nm or 3.0Nm steppers TBD

One key question for me is - should you leave margin on the driver current rating over and above the motor's datasheet value? All the above motors are rated on their datasheets at 4.0A or 4.2A typically when wired in parallel mode. Normally I guess I'd be looking to have a driver that is rated at maybe 5A or 6A minimum, but you certainly seem to have to pay a premium for these. Or maybe the choice needs to be directed by the supply voltage you want to use? My router runs on 68v for speed, so I wonder if that might actually dictate some of the choice?

Either way, comments and suggestions would be most welcome!

Cheers
Graeme

Clive S
04-03-2017, 05:51 PM
Greame. You won't go far wrong with AM882 drives and they will handle 68v

Neale
04-03-2017, 06:27 PM
My impression is that that they are the cheaper, older, version of the EM806. Basically, same functionality and voltage/current ratings; the firmware is not quite as sophisticated but it's going to need a fairly demanding application to tell the difference. I'm using EM806 very happily, but only on X and Y axes where I'm concerned about things like stall detection - especially on master/slave X axis. I doubt that using AM882s would make much difference, but I previously bought m752 for my first router just before discovering that a) they were about to become obsolete and b) digital drives are much better, and I probably went a bit too far the other way this time. However, I am reusing one of those 752s for my Z axis where the drive requirements are a lot less demanding.

My impression is that if you want a nominal 80V driver to run reliably on 68V, there isn't really that much choice out there. 882/806 - and then what else?

JAZZCNC
04-03-2017, 07:14 PM
Graeme clive is correct that AM882 are the way to go but to answer your questions about current and Voltage. Out of the two having higher safety margin on voltage is most important. Roughly 10% safety margin is advised but more is better.
Regards Amps then what's more important than safety margin is being able to select the correct motor amps. Most drives only give you few options on current selection and usually there's never one exactly same as motor rating. In this case it's best to select next lowest. However the AM882 allow you to set (via software) current in 0.1a increments so can get exactly right.

Won't go wrong with AM882

GND
04-03-2017, 09:07 PM
Thanks Guys - it's always useful to get a sense of what is going to do the job, and is well proven by real experience. I'd picked up on the EM806 and the AM882 from previous mentions, but hadn't appreciated how they related together, nor into the grander scheme of things. Sounds to me - with an eye to good value - that the AM882 is the way to go.

So, the next question is where do you guys suggest I get them from? Google and Ebay don't seem to throw up any options in the UK, so is it a case of ordering from a trusted supplier in China? Slightly fearful of counterfeit ones, so a reputable source is important here I guess. Either way, any suggestions gratefully received!

Jazz - thanks also for the answers to my voltage and current questions. That makes sense! I recall now that you have to include a bit of margin on voltage for the back EMF, but knowing that 10% is reasonable is a great pointer. Hence 80v drives for my 68v supply seems ideal. Good points also on the current - if the driver limits this, then it is essentially under its control, so less need for much margin. I like it when things all make proper sense!

Justin Pentecost
04-03-2017, 11:03 PM
I have AM866's here so I must have bought them from Gary at Zapp Automation. However his site is not showing any only the EM806's. You can be sure it's not a knockoff if it comes from him ..

Justin

JAZZCNC
05-03-2017, 08:43 AM
I have AM866's here so I must have bought them from Gary at Zapp Automation. However his site is not showing any only the EM806's. You can be sure it's not a knockoff if it comes from him ..

Justin

Never heard of AM866 you sure got that right.?

Graeme I've bought 100's from China and never seen Copy of the AM882 or EM806 so don't worry about buying from china. Ali express is the place to find them.

Justin Pentecost
05-03-2017, 09:59 AM
Never heard of AM866 you sure got that right.?

Graeme I've bought 100's from China and never seen Copy of the AM882 or EM806 so don't worry about buying from china. Ali express is the place to find them.

No I meant AM882, I would try and blame fat fingers but it's not even close enough for that .. Shall we settle for stupidity?

GND
05-03-2017, 10:52 AM
Thanks Jazz - there are certainly plenty of AM882's listed on there. Curiously no EM806's though. Sounds like I shouldn't be worrying about non genuine ones, which is good to know. I've not yet used Ali express, so was just a bit cautious. I have however bought kit from China on eBay, so not complete beginner in this!

So something else occurred to me. I'm more then happy that the 80v drive is the way to go for the 68v PSU router. For the mill - which for the record is going to be something along the lines of a Sieg X2 conversion using 2Nm steppers - does this require such a high voltage drive? My understanding is that it won't need the feed and rapids speed that a router does, and so a lower voltage for the drives is more in keeping. And that in turn means less expensive stepper drives. Or have I missed the point?