I am using the Stepper library. I basically just made some minor edits to the "Motor Knob" example provided in the Learning section.
I changed the pinouts to work for my motor, and adjusted the number of steps. I also took out the delay statement.
The issue is, I can really only get my stepper to turn at about 4Hz/revolution. Any faster than that and it starts acting epilectic, or freezing up and whining. I can go slower though, no problem.
The other issue: it's not too hard for me to stop the motor shaft from turning just by holding onto it with my bare fingers.
So, is this typical for steppers? Would performance improved if I put an H-bridge and a seperate power supply in my rig?
Thx
btw: the Stepper library is a lot of fun. Very easy to use. I'm a big fan.
Steppers are slower than dc motors/servos
You rarely see steppers used in printers anymore, 'cause the dc-motors with rotary encoders are so much faster and cheaper.
as for max rating, consult datasheet the motors are as different as the manufactures are many. Don't say: but its NEMA-motor, because that is just an American standard for outer casing of the motors, where holes are and min/max dimensions.
Powering a stepper without an external supply would often cause them to run slow and weak. They are obviouslycan be faster, as in printers they were faster. I use the motor shield from ladyada/adafruit and it is rather underpowered for any of the steppers that I have.
floppymotors did not have to spin much weight (almost zero) nor did they have to go fast as the data density was not great thew hole disc was just 720K or 1.44Mb max
Would performance improved if I put an H-bridge and a seperate power supply in my rig?
Almost certainly (assuming it's bipolar. If it's unipolar, you need a transistor array like the ULN2003).
More to the point: if you're not using an external driver, it's very likely that you'll fry the CPU.
If you use an H-bridge, be aware that the most popular ones (like the L293D) use bipolar Darlington transistors to drive the motor. That means that the output to the motor will be about 2-3V less than the power supply going into the chip. That's not a huge deal when running the typical 12V motor off a 12V supply (unless you're using the motor near the limits of its torque ouput), but it does make a big difference when you're driving a 5V or 6V motor. You may need to up the voltage of the power supply to allow for the voltage drop inside the driver chip.
So if this stepper came from a floppy drive, it was probably not intended for more than 360 RPM.
He was probably talking about the old head-positioning motors from 5.25 floppy drives, not the spindle motor.
Regarding those who have such drives:
Please pass those drives onto a local hobbyist or via a vintage computer forum - especially if the drives are the old 360K (or smaller) variety; if you tear them apart (unless it is obvious they are fried in some fundamental way), you are likely pitching money away (there's a place in California that sells old drives like this, mainly for replacement on old industrial control computers - they sell for a pretty penny, depending on the drive).
I collect older 5.25 drives, mainly for use in my TRS-80 CoCo emulators and actual CoCo system. BTW - if anyone has any old 8" or 5.25" fixed/hard sectored floppies/drives - I could use one or two - I have an Altair with a floppy drive controller, but it is for fixed/hard sectored drives (yeah, I know I would need the luck-o-gods to get this)...
Yea, I remember that NASA was hording and collecting motherboad bits , cpu's from 286 and 386 computers, for one of the spaceshuttles, as it was getting hard to find parts in good working order and they could not upgrade those computerparts easily ;D
You know, come to think of it, I don't think it was from a disk drive. I tore these out about 10 years ago and put them all in bin. They had some strips attached to the motor shaft to help a part sweep. Maybe like platter heads for an old HD. Can't remember.
You know what though. I've had a lot of trouble getting rid of old machines in the past. I have a fully functioning C-64 WITH DISK DRIVE, software and modem. I had that on Craigs for a month for thirty five. No takers.
Can you blame them? Now there is a C-64 emulator for the iPhone. :-/
Put those drives up on EBAY to get money for the motors you REALLY want.
You need to suck up to some of our members still living in Silicon Valley: some of the best e-junque dealers are gone now (Alltronics is still doing mail-order, but RA, Triangle Tool, and others just closed up completely), but I hear that a few are still in business. Plus the monthly computer/electronic swap meet may still be going on at Foothill College, which was an amazing source of all kinds of tech stuff when I was living there: everything from WWII-surplus radios to engineering prototypes of gear that couldn't be shipped overseas without a federal arms-control export license.
Sad to see them disappear ... there is no place you can walk into for Surplus stuff anymore in Atlanta.
I'd love to see a day when some of these appear in the UK. Sadly I don't have anything close so almost all my stuff is new or just some old printers (or scanners! I love scanners!).
There is some video of the stepper I'm asking about here : quinnzblog: Stepping Up. It's not the motor you see in the first 30 seconds of the video, but the one hooked up to the Arduino after that.
Note: this was before I got the feedback about the Darlington array. Thanks!
