Connect with us

Stepper motor raw / with driver / programmable driver

Discussion in 'Sensors and Actuators' started by bogus, Nov 7, 2013.

Scroll to continue with content
  1. bogus

    bogus

    4
    0
    Nov 6, 2013
    Hi all,

    I'm afraid I'm a bit new to this stuff, so apologies if my questions are naive, but, I'm spend hours and hours looking into stepper motors and how they work and how you use them and I have a few puzzlements I don't seem to be able to entirely straighten out!

    I've read plenty of stuff about how a stepper motor works, I am quite happy I understand its operation, and could write a little program to light up the right coils in the right way to make it move in whatever way... but I notice that in all such cases of people actually doing this, a driver is always used, and, first question, as far as I can see the only point of the driver in this case where you are using a microprocessor to light up the right coils, the only point is to drive the motor from a different power supply, not directly, the driver doesn't seem to add any intelligence as such? Correct? Or am I missing the point?

    I've also found out about this A3967SLB driver, which seems to provide a simpler interface, allowing you to send a simple pulse to turn the motor. This is nice, it's easier, requires less I/O lines, etc, so jolly good.

    So my second question is, are there MORE intelligent drivers out there, drivers you can program or configure to operate in a certain way, and then control quite simply. The most obvious example would be to turn a stepper motor into a normal motor so that you could turn it on and off with a high or low signal... This wouldn't necessarily be a complete waste of time of course (as far as I can see) because you still have the precision of a stepper motor, predictable speed, and fairly accurate measurement of number of turns if you have a good clock and have it setup to operate at a known speed... More useful still if you could reprogram the driver to change the speed at any time whilst also controlling it. Also such would let you control many more motors by means of multiplexing. So, second question, since it's become a bit confusing what I'm actually asking, is are there drivers to do this stuff? I can't find any information about people doing it I must say...

    Regards...
     
  2. GreenGiant

    GreenGiant

    830
    6
    Feb 9, 2012
    The main reasons you use stepper driver chips is for increased current (holding and peak) most microcontrollers can only provide a very little mount (usually in the 10's maybe hundreds of milliamps) while stepper drivers can provide a lot more (smaller ones can even put out up to 2A).

    The other reason is increased speed at a lower cost, in order to turn a micro stepper (something like 1-2 degrees per step) you need to increment the stepper 180-360 times to make one revolution. With a microcontroller this would take up an enormous amount of processing that could be used elsewhere while stepper drivers you just apply a signal to until it reaches where you want to go.

    We use steppers to control some of our automation at my workplace, we run some of them into the hundreds of RPM's using stepper drivers, and some need as much at 4 amps of current for holding and motion, and some need a combination of the two (high speed and current), we do have microcontrollers but they do a lot of other things and cannot handle turning 180 step motors at 100RPM at 24V 1.5A.
     
  3. bogus

    bogus

    4
    0
    Nov 6, 2013
    Right, brilliant, thanks for the reply, that makes sense. Seems like everything I thought I knew is right then, and my expectation that the stepper motor controller should do a lot more is at least mostly true too, it's just that I've not found any information about people using the full power of stepper motors.

    I guess I'll have to pour some more time into the incomprehensible chip data sheets until light dawns, and get get a chip to experiment with. Or maybe a few, in case I blow it up ;-)
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,268
    Nov 28, 2011
    Re your second question, about stand-alone stepper control signal generation ICs. I haven't heard of any. That's not to say there aren't any, but all the stepper motor drivers I've seen require at least two inputs which are driven by a microcontroller. This is the way to get the best flexibility in any case. You can tailor the behaviour to the characteristics of your stepper motor, to get reliable and rapid acceleration and deceleration without cogging (or whatever the proper word is for it), and you can get the optimum amount of torque by controlling the overlap times, I think.

    I tried to find some stepper drivers on Digikey, but I only found documents for boards that include preprogrammed MCUs on them. They could be of interest to you though. Go to http://www.digikey.com/product-sear...er-boards-modules/motor-driver-boards-modules and in the Type field, select only the two Stepper options, and click Apply Filters. Most of the products are non-stock and obsolete, but you may get some ideas from the data sheets, which are linked near the left side of the results table with the PDF symbol.

    Good luck! Please keep us informed.

    Edit: I spoke too soon. There's a whole section of ICs at http://www.digikey.com/product-search/en/integrated-circuits-ics/pmic-motor-bridge-drivers with lots of different characteristics.

    Most of the ICs have a control interface that's just described as "parallel", which doesn't tell you anything about how smart the device is internally and how simple it is to control. You'll have to look at the data sheet for each device to find out that information. I can't suggest any of them; I don't know much about stepper motor drivers.

    Looking at the devices that don't have a "parallel" interface...
    The Rohm BD63860EFV at http://www.digikey.com/product-detail/en/BD63860EFV-E2/BD63860EFV-E2CT-ND/2131128 drives a two-coil bipolar stepper and includes a lot of smarts.
    The STMicroelectronics L6470 at http://www.digikey.com/product-detail/en/L6470HTR/497-10812-1-ND/2469160 and L6472 at http://www.digikey.com/product-detail/en/L6472HTR/497-12964-1-ND/3194670 and L6474 at http://www.digikey.com/product-detail/en/L6474PDTR/497-13327-1-ND/3661285 are very smart and require an SPI (serial peripheral interface) connection to a microcontroller.
    The STMicroelectronics L9958 at http://www.digikey.com/product-detail/en/L9958XP/497-11627-5-ND/2746838 is similar.
    The Trinamic TMC260 at http://www.digikey.com/product-detail/en/TMC260-PA/1460-1042-ND/4399651 is also smart with an SPI interface.

    All of the others use a parallel interface. You would really have to look through the data sheets, or do some clever Googling, or find someone who has a lot of knowledge in that field, to find whether there's an IC that does exactly what you want.
     
    Last edited: Nov 8, 2013
  5. bogus

    bogus

    4
    0
    Nov 6, 2013
    Ahh, wow, yes, ok, I can see some of these sound sensible and very feature rich indeed. Thanks for this, I think I just didn't really quite know enough to google the right things before somehow. Doing it by SPI sounds much more sane to me compared to using large numbers of outputs per motor.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-