View Full Version : Chip to control small stepper motors
07-19-2006, 07:19 PM
Here's the application. A bunch of small containers (up to 60), each with a lid that is opened with a small stepper motor. You select the "recipe" and the lids on the appropriate containers open. Each lid opens in the order that you should use the part and after you've picked the part, you·brush your hand (holding the part) past a sensor. This closes the lid on the current container and opens the lid on the next. The steppers are small - 60 Ohm and I'm driving them at 12 Volts. No rocket science here...
I'm not keen to solder 60X8 transistors 60X2 diodes, 60X2 resistors etc and I don't want a PCB the size of a Rugby (American Football)·field·so I'm looking for a single·IC that will control·each stepper. Either a dual H bridge or (preferably) something more intelligent. I would prefer 1 IC per stepper. It·should be a common IC.
What is suitable·IC?
Has anyone had experience with the L6219?
Kind regards from Kwa Dukuza in Darkest Africa.
A hobby servo would be much easier to use. I don't know if you can change now...
If the steppers are uni-polar and if you are only using 1 stepper at a time, you should be able to use 1 H-Bridge that connects to ALL the steppers, then use a FET to connect the common for each stepper. Only the stepper whos FET is turned on will move.
Cheap 4-digit LED display with driver IC·www.hc4led.com (http://www.hc4led.com)
Low power SD Data Logger www.sddatalogger.com (http://www.sddatalogger.com)
"Remember, you are unique, just like everyone else." Unknown.
I use the SN754410 for bipolar (4 wire) steppers; its a single chip solution. I beleive the specs (from memory) 35V, 600 milliamps continuous. You can also stack them for more thru-put. Pick your package to suit for size. Oh, US ~$1.50 at Digikey.
Kronos Robotics has a wiring diagram on line.
07-19-2006, 09:05 PM
Check out UCN5804. Its good to 1.25 amps per phase.
07-19-2006, 09:21 PM
Your comment on using a FET is very interesting
- Rough industrial environment... I felt that Robust steel stepper motors would survive better than plastic servos
- Plenty of them... up to 60 bins per unit, possibly a couple of units. In South Africa, prices are about US$5 for a stepper Vs US$20 for a Servo. Even if the chip costs another US$4, I'm still $11 better off or $660 per unit. $660 is a significant sum for us here, 20 days wages for an average factory worker.
- Bipolar Steppers are available whereas 5 wire steppers are rare here. Maybe I could import uni-polar and use FETs
First Prize is a small PCB with 1 IC and a 4 or 5 pin connector to the controller. This PCB is mounted on the stepper which makes up the hinge of the lid of the container.. When the lid fails, you unplug the old unit and plug in a new one. Hey... we used to be a lot like the Amish, "make, mend or do without" but we too are becoming a throw-away society. The tentacles of your American society are reaching down, way down, even into Africa.
Kind Regards from Kwa Dukuza
07-19-2006, 09:31 PM
Thanks LSB and Bobledoux
They're both look suitable at first glance and an equivilent of the UCLN5804 is available in South Africa at US$3.
Wow, I only asked for help 2 hours ago!!!
Kind Regards etc etc..
07-20-2006, 03:03 AM
You could adapt Bean's idea to bipolar motors, construct a single H-Bridge or purchase a heavy duty H-Bridge. Then use analog switches of sufficient duty to drive a stepper motor and connect the terminals of all of the steppers with the output of the H-Bridge in parallel fashion. You would then turn on the analog switch to those steppers on the lids you want to open. The current rating on the H-Bridge will dictate how many lids you could operate simultaneously.
The only potential problem with this setup is damaging the analog switches with inductive kickback. You can't use the diode solution because the current must be able to flow in both directions. There are some devices that could work which are basically capacitors that use a gas dielectric which breaks down at a designed voltage. Also back to back zeners should work.
Post Edited (Paul Baker) : 7/19/2006 7:10:12 PM GMT
07-20-2006, 03:30 AM
I don't know if this is overkill or not, but please find attached an addressable relay driver which can handle 150 mA per port, and can be expanded. It shows as one of the applications uses "stepper motor driver" as well.
07-20-2006, 03:12 PM
Hi Paul and Bruce
The relay driver is a very useful chip, an intelegent ULN2803!!! - Thanks (I'm going to put a couple in my inventory)
The L6219 stepper ic has two enable lines which means I can do exactly what Paul suggests but with no additional components. Pulse the 2 phase pins on all the stepper boards and only pull the two enable pins high on the motor I want to turn. Pull 1 enable pin low to hold the motor in a position (coil energised to hold the lid open) and pull them both low to allow the motor to turn freely.
- The micro then needs 2 pins which pulse the phases and just 2 outputs to select the stepper being used
- Each stepper board has just 7 wires, 2 power, 1 earth, 2 phase pulses and 2 enable inputs
- The stepper board has 1 chip, 7 capacitors 6 resistors and a 7 way connector
An SX48 development board can easly handle 20 steppers. If I wanted to be adventurous, I could use a couple of shift registers to switch the enable pins on the steppers but for maintenance reasons, a development board per 20 makes more sence.
It's interesting how this project has got simpler and cleaner with the advice and assistance from you guys
Kind regards from the place where Chaka Zulu built his famious Kraal (Zulu village) 190 years ago.