Hello, I am going to need to control about 50 mini stepper motors (4 wire bipolar) and need some advice. These are the small steppers inside a CD drive (see attachment) so they don't require much current. I don't need to control them at the same time so I was thinking I could use several multiplexer chips to switch the control lines. Anyone accomplish this before? Any advice on if it will work?
Thanks, Ben
It will almost certainly work. I would use shift registers instead of multiplexers. If you use shift registers that have sufficient current handling ability you won't need separate drivers. How much current do the coils draw if you put 5V through them?
Hi, How many steps/second do you need? Can shift registers keep up??
terryking228:
Hi, How many steps/second do you need? Can shift registers keep up??
If you connect the shift registers to the SPI port you can push data out at 8 megabits per second. That would get you 40,000 updates per second of all 200 output pins. I expect that will be fast enough.
I'm having trouble finding much info on the specs of these but I did find something on alibaba which is some kind of Chinese supplier. I believe the current requirement is around 200 - 300mA. They don't have to move fast either. I'm not concerned with speed. They will move to a position and then sit there all day.
The TPIC6A596NE (20-pin DIP) can handle 350 mA. http://www.ti.com/lit/ds/slis094a/slis094a.pdf Unfortunately they are "Open Drain" outputs so they can sink 350 mA but can't source current. I think this means that you can't use them to drive a bipolar stepper where you need to reverse power to the coil (See: Stepper Motors – code, circuits, & construction).
How's your budget? You might need a Dual H-Bridge chip per stepper. At least then you could use cheaper non-driver shift registers.
If you have not gotten the steppers yet, are there any unipolar (5 or 6 pin) options? Those would work with Open Drain or Open Collector outputs.
John I see what you mean, if I use the bipolar i will need to switch the current direction and will need an H-bridge. I haven't purchased the steppers yet, I'm still trying to find the cheapest solution. I will post my results once I figure it out.
These might work. You can get 50 for $80.90.
Any luck with this? Turns out I am using similar aliexpress mini stepper actuators, and want to control 10 to start, but up to 20 or so in the future.
it looks like people recommend this for a stepper:
but it's $2.25, and for 10 cents more you get double the stepper control with an Allegro chip (and it does 1/4 microstepping if you want):
http://www.allegromicro.com/Products/Motor-Driver-And-Interface-ICs/Bipolar-Stepper-Motor-Drivers/A3988.aspx
veedub88:
I'm having trouble finding much info on the specs of these but I did find something on alibaba which is some kind of Chinese supplier. I believe the current requirement is around 200 - 300mA. They don't have to move fast either. I'm not concerned with speed. They will move to a position and then sit there all day.
Whoa, you can't drive that level of current for a bipolar motor without H-bridges for each motor -
unless there's a shift register that can both source and sink such currents.
The modern approach would be to use SMT stepper motor drive chips (as the current is low enough), and
for instance there's a dual stepper motor driver DRV8821 which would reduce the chip count - still need
an Arduino Mega to provide enough step/direction outputs (well, not really enough!).
[ Yours is an application where unipolar motors would be far easier - one ULN2803 per two motors fed from
a string of 595 shift registers... ]