EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: electronics-whiz on January 02, 2015, 10:02:59 pm
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I have a mainboard from an old Epson dot matrix printer. I have some interest in building a stepper motor driver, this is looking like one of the better boards to salvage parts from.
It has an STK 6722HZ chip, and heatsink for it. I found a diagram for it with google images, I couldn't locate a datasheet though. (Diagram is attached)
This chip seems to be getting some input from a toshiba TMP90C041N. P17 on the STK chip seems to go to an epson ASIC.
The toshiba one I mapped out first pin is for the STK chip, 2nd will be the toshiba. P5 (STK) ->P9 (toshiba), P6->P11, P13->P10, P14->P12.
I'm not sure what the toshiba chip is as it seems to interface with the parallel port interface chips, a couple of things that look like RAM, and a EEprom, and a couple Epson ASICS that run transistors for a stepper, head, solenoid for paper hold bar. It's socketed like the EEprom so thinking it's some sort of a CPU type device.
If it's simpler to go another way that's fine. The STK chip I think would be useful in another setup too. I just don't know how to get the inputs. I think most these stepper ICs need some sort of pulse rate, and I don't have that.
I also saw a resistor and diode that looked like connected to the stepper's ground I don't know that's a safety or what.
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Are you doing this just to learn stuff, or do you have some specific application in mind, which needs a stepper driver?
If it is the first, then first look at Wikipedia Stepper Motor article (http://en.wikipedia.org/wiki/Stepper_motor) to learn how to create the pulses to drive a stepper. Then you can go find a small stepper with low power requirements like this one (http://www.adafruit.com/products/858): you can then drive it with a ULN2803 darlington transistor array and an arduino or an AVR chip or a PIC chip...
If it is the latter, then what are the requirements? How can anybody tell if this IC will satisfy or even work for your needs? And anyway, I thinks that salvaging old chips to create a new solution in the case of stepper motors rarely works to your advantage. With the cheap Allegro A4988 or TI DRV8825 chips, there are readily available driver boards on the internet for less than US $10, that are very versatile and can handle small to medium loads (about 2A per winding). And you need only 2 outputs to drive them (direction and step pulse) as compared to 4 for your chip....
So you get to choose which way you want to go depending on your needs.
Regards,
Todor
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I have no real application at this point. I have lots of stepper motors of various forms. Some 4 lead, some 6, this chip uses 6 which I saw somewhere will also run a 4 lead motor. At some point I'd like to find a way to use them for something like a homemade 3D printer, or run some things that printers have in them like pumps, etc.