Cheap stepper motor and driver
Leon
Posts: 7,620
I bought a stepper motor and driver board which has been mentioned here previously from a UK supplier (£5.19 with free postage) which seemed like a good deal, but I just found the same thing from a Hong Kong supplier for £1.66 with free postage:
http://www.ebay.co.uk/itm/5V-Stepper-Motor-28BYJ-48-With-Drive-Test-Module-Board-ULN2003-5-Line-4-Phase-/200712530295?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2ebb662977
which is incredibly cheap.
The motors were apparently intended for controlling ventilation louvres, which explains their low cost.
I'm working on a simple assembler test program for a PIC16F88, primarily because I had a suitable home-made prototyping PCB and it seemed to be a waste of a much more expensive Propeller proto board.
Because of the gearing these motors aren't much use if a rapid response is required, but they are ideal for educational purposes.
http://www.ebay.co.uk/itm/5V-Stepper-Motor-28BYJ-48-With-Drive-Test-Module-Board-ULN2003-5-Line-4-Phase-/200712530295?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2ebb662977
which is incredibly cheap.
The motors were apparently intended for controlling ventilation louvres, which explains their low cost.
I'm working on a simple assembler test program for a PIC16F88, primarily because I had a suitable home-made prototyping PCB and it seemed to be a waste of a much more expensive Propeller proto board.
Because of the gearing these motors aren't much use if a rapid response is required, but they are ideal for educational purposes.
Comments
with Forth on a Propeller, you can deal with what the stepper motor is doing in real time. This really speeds up tasks that require accurate positioning and calibration. Once you lock in the right rates and positions, you can extend your Forth words into a complete routine.
Either PropForth or Tachyon Forth are available.
Well i think its great man and as you define it should be run in same manner as you define. I will definatly try it because it seems to me very intresting.
Thanks for the find.
Plan to order a bunch today to drive many small ball valves to modernize (network) our building's water based heating system.
These should be perfect for that, and I sure like the price.
Cheers,
Peter (pjv)
http://en.wikipedia.org/wiki/Ball_valve
They should be ideal for that, so long as you don't need too much torque. Of course, the gearing gives a lot more torque that you would get from similar motors without gearboxes. I found the data sheet:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDIQFjAA&url=https%3A%2F%2Fbitbucket.org%2Ffdion%2Fpi-a-sketch%2Fdownloads%2FStepper-Motor-28BJY-48-Datasheet.pdf&ei=pxM6Uee4G4yV7Ab2roDACQ&usg=AFQjCNHR_elifp8Bc6S93VORL4Oh7b5KxA
That is for a 12V motor whereas the one I've got is marked 5V, but it should be OK for mounting dimensions etc.
http://www.ebay.co.uk/itm/LM2596-Step-Down-Adjustable-DC-DC-Power-Supply-Module-New-/170734419936?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item27c0907fe0
DC-DC step-down PSU for £1.15
Most of the time, positioning doesn't have to be a fine grained as a stepper provides, and speed is a bit of a non-issue as well. I like the idea of using a ball valve is that don't tend to stick in an open or closed position. That stickyness of a conventional faucet with a valve seat makes electronic control much harder to implement.
Yes I'm using them on my robot and so I just checked. I dont have anything to measure angles but-
I get backlash of 1/16 inch.
Wheel diameter is 2 7/8 inches.
So circumference is 9.022 inches.
backlash = 360 / (9.033 x 16) = 2.5 degrees.:nerd:
(hope I'm right)
Dave
And while I'm at it I would say they are ok for non critical use. The torque is not great - it seems a lot with the shaft turning and you pinch it with your fingers, but with a 3 inch wheel attached it is easy to make it miss a beat. Actually I'm driving them at 10volts and they get warm but as long as they keep going I will continue to abuse them.:thumb:
Dave
I expect they'll be fine for my purpose. I've asked for 100 to be shipped so hope t have a lifetime of spares. I plan to run a serial network around the building ...propeller driven of course... to sense temperatures, control these motors as heat zone valves, control lights, building access as well as employee task logging. Figure a hundred nodes or so, and probably controlled by Hanno's 12 Blocks. Ought to be a fun project.
Cheers,
Peter (pjv)
I suspect that if they are not quite right for Peter(pjv), there will be an easy resale market.. especially at these prices.
It might help significantly to really deliver 5 volts to the motor. The ULN2003 and related Darlington chips can have an internal voltage drop of as much as 2 volts, so to get 5 volts to the motor, you might need to provide 7 volts to the ULN2003.
Backlash and plastic gears.......
Well, you can't have everything for bargain basement prices.
Here is the premium alternative.
http://www.stepperonline.com/geared-stepper-motor-c-4.html
I ordered 4 of these a while back, still have not tested them. I want to build a lidar system based around a wiimote camera, and I need an accurate way to adjust the angle of the laser. I had planned on using one of these with a hi res encoder from a printer. The amount of backlash may just kill this idea though, im not sure I would think if one had a good enough encoder for feedback, the dead band could be totally compensated for. Ive also been looking in to brushless hard drive spindels.
1. It limits the ability to hold an accurate position. Just consider these motors a bit sloppy.
2. If you are doing a lot of forward/reverse seeking, it bangs up the gears and these are plastic gears that are not very durable.
For Peter(pjv), turning small ball valves may do fine. With ball values, I think you can open and shut the valves by always rotating in one direction if you must. That might resolve all the backlash issues.
I doubt if you are going to get minimal backlash for bargain basement prices. The stuff I posted a link to seems pretty good, but for the absolute least... a direct drive stepper would be the best.
After all, no gears means no backlash. But you do have to figure out what the holding power of your stepper motor is and how you are going to provide for it.
erco NEVER said that. Feel free to review post #9.
The truth is you should read the specs from some of the quality geared stepper motors and see what their backlash is.... then compare. See my Post #14.
I am in love with geared stepper motors... especially the ones with planetary gears. These are really useful work horse devices, not junk.
http://forums.parallax.com/showthread.php/141149-3-Stepper-Motor-amp-Board?p=1163683&viewfull=1#post1163683
Hanno
Bill
I tested one from the batch I ordered, and for the price, I like them. At 5 Volts (the rating on them) the torque is not huge; that is you can "just" stall them with your fingers using a really tight squeeze. At 12/15 volts, I'm sure you could not, but then you'd have to be careful not to leave them energized when not stepping. Another benefit, for my application at least, is that when turned off, you can still force a rotation by hand without apparent damage. This will allow me to "over-ride" the setting of my ball valves in case of power failure.
There is a tiny amount of slop in the gearing.... certainly not an issue for me.
Cheers,
Peter (pjv)