So I have a need to just a laser in very small steps, 1/2 degree would be awesome. I see Ron has half steps going, but the listings on ebay for these motors dont say how many degrees each step is. Now knowing much about stepper drivers is it possible to use the darlington array based drive board to achieve quarter or eighth steps? I just need something small and cheap to accuretly move light objects like lasers, and optical sensors in very small steps. I was originally going to use a micro servo, but, there are issues with jitter, and i would like 360 degree motions, also a servo moves in 1 degree steps from what I understand.
I looked through here and didnt see much besides erco said the output shaft gives 2000 steps, that seems like a really accurate motor for this price, wouldnt that be .18 degrees per step???
Since seeing his post, I've been on the lookout for these encoders. I've found several in a printer I took apart. I keep meaning to use it to precisely point a laser. I'm not really sure how I'd make this work, but I think it would be interesting to see how precisely these encoders would allow a laser to be aimed.
You might want to keep you eyes open for these sorts of encoders.
Also keep in mind you can increase the positioning resolution of a stepper by gearing it down (though backlash will still be a problem).
I was originally going to use a micro servo, but, there are issues with jitter, and i would like 360 degree motions, also a servo moves in 1 degree steps from what I understand.
If you have a good power supply, you should be able to keep servos from jittering. Your 1 degree estimate seems about right, but theoritecally a servo that turns 90 degrees over a pulse range from 1000us to 2000us could have the resolution of 0.09 degrees. I doubt there are many (if any) servos that could really reach this accuracy but I'd think half a degree should be possible if one had a high quality servo and were very careful with the hardware and software.
Hmm well I ordered some ebay 3 dollar Chinese micro servos lol ! I really doubt these will be very useful for my needs, they were for crude testing. As far as printers go, ive torn apart TONS, I have a few motors with those hi res encoders on them, but like you i dont know what to do with them. Im not sure how they work or what kind of sensor i would need to read them accurately, Ive kept all the optical interrupts from these printers, but im not sure which ones went with which motors. I have a printer waiting to be salvaged though, and I know it has one in it. The thing is Phil told me in my encoder thread that reading a 100 count wheel is very ambitious and he had to step from 50ish to 30ish counts. It looks to me like the slot interrupts in a printer are fairly standard, so im assuming that there is some other hardware involved. I may try connecting one to a scope and seeing what happens.
This is basically for a DIY laser range finder, using WiiCam. According to Gareth you have to adjust the lasers angle for short or long distance, So the idea is to mount the cam on a platform that rotates 360 degrees, then set the laser next to it, on its own rotating platform, the idea is the wiicam stays fixed while the lasers angle can adjust, wile the hole device rotates 360 degrees. Since one would need to do pretty precise math that involves knowing the exact angle of the laser something that can adjust the laser 1 full degree at a time (at least 1 degree seems resonable, cant think of why you would need more), with no backlash is very much needed, this laser need to be where its suppose to be, weather it got there by a stepper or a dc motor with encoder. Now whatever solution I use to rotate the whole laser/cam assembly in a 360 manner is the one that need to 5 degree or less movements, as this will dictate the max resolution of the laser scanner. These cheapo steppers paired with an absolute encoder may be the ticket, if I understand this right. The encoder can give me my starting angle, then I can keep stepping taking a scan every .18 to .5 degrees, when I hit the place on the encoder telling me ive done a full 360, I stop the laser, then stop the motor. When the motor stops the backlash will happen, but I will already be done scanning, and ill be able to tell its stop angle via the encoder. Does this sound good in theory or am I misunderstanding some of the details?
What I have to work with as far as money, is a $25 dollar ebay gift card, which I also need to buy a better laser, even a 2 dollar laser pointer is an improvement over the ebay laser diodes I currently have, the culminating lens (if thats what it even is) is a joke and my laser blobs to the size of a quarter after 10-15 feet. Im also thinking I want to get IR this time.
So anyways just want to get my ducks in a row and find the right parts to attach to the stingray for later use, there has been to many times I wasted money on either A, junk, such as these laser diodes or B, bought something that doesn't quite fit the bill ex, these micro servos. Ive got most of everything I need for this bot except some type of hi accuracy pan or pan/tilt devices.
According to Gareth you have to adjust the lasers angle for short or long distance
Indeed...indeed..... Its a while since i linked my Wii-Camera up..... however new ideas have been brewing in the background :-
(1) Place extra lasers (all at different angles) on the (stepper/servo) mount .... the Wii camera will detect 4 (lasers are cost effective at momo)
If they are set in 4 different plains - then for example ...the top quarter of the Wii camera horizontal array will detect one laser....the 2nd quarter detects second laser ....etcetcetc
This would allow for long, mid-long, mid and short range detect simultaneously....
If you set the horizontal detect to be very narrow then it would be possible to filter out some of the ambient IR noise that can show up.
On an inspirational note :- I am well impressed by the results i gain with my Wii camera..... and even pointing the thing on the floor away from you gave quantitative readings (ie ultrasonic or IR will not do this)
(2) $3 steppers....... (go for it before i do :-)....... I would use 2 back to back Wii cameras and scan just °180
I would then attach a spring to the laser arm and it would pull back on one side to keep deadband always in the Positive (or negative if you know what i mean) with °360 its a tad more difficult.......
Ahh.., the aroma of magic smoke. I destroyed a ULN2803 after using it over a month. It could've been because I used fresh batteries and let my robot run longer than I usually do so I could find any bugs. I think to myself "erco! Check with erco!"
I've decided to get a supply of drivers for 12V unipolars. I'm looking for reliable suppliers and their shipping times. Who are you buying from at the moment?
After several months of fruitless diddling with my cheap stepper motors/controller modules, I gave up and ordered two replacement motors. Set them up this morning and they worked perfectly. Looks like I got two bad motors first time around. Ah well!
More experimenting this morning. Connected the stepper motor/board to my net book and loaded the code stored on the HD and the motor refused to turn. It just kind of vibrated a bit.
Kind of frustrating since the darned thing worked Thursday!
Sorting through everything, trying to understand what was (wasn't) happening, I noticed a small difference in the code. In my original attempts to get the motor running I used the code beginning with:
' {$STAMP BS2}
' {$PBASIC 2.5}
'spins stepper motor about 180 degrees & back
'uses P0-P3 to ULN2003 controller board
'press BoE reset to cycle
DIRL=00001111
B0=1
On Thursday, I cut and pasted code from this thread, but the variable B0 was defined B0=2. With a value of '2' my motors run (even the ones I thought were dead). I'm not sure why this is. Is a pause of '1' too short for the motors to react?
Anyhow, now I have four functioning steppers (but only two controllers :-< ). Yay!
Anyhow, now I have four functioning steppers (but only two controllers
You could make a controller for those motors out of a darlington array* which are a few bucks. Probably any transistor has enough umph because they're only 5 volts and I can't imagine that they use much current. For a bigger unipolar stepper I've used TIP 120 power transistors which would be complete overkill for them.
This Stepper is requiring an adequate delay, otherwise they simply vibrate. There is a post somewhere reporting an asymmetrical limit (you need a longer delay in one direction).
The delay limit is also different if you are full stepping or half stepping. I would suggest to start slow, and then search a limit.
Massimo
Amanda: IIRC, I was getting good no-load results using a 1 ms pause with my BS2. See code in post #1. Try running higher voltage than 5V for snappier response. Just remember to turn off the coils when you stop the motor or you can overheat. The eBay ULN2003 controllers work fine.
Pretty sad that you got 2 bad motors out of the gate. I'm in China right now. I'll make sure the locals hear about this!
They might just like a 1 ms pause at 12V! IMO they're already slow enough with a 1 ms pause, so anything longer gets glacially slow...
Seriously, I have used 12V (3 Li-ions) just fine on 5V motors. Don't be shy with voltage, just careful.
Running them from a BS2 BOE using a 9.6v battery. I'll switch from Vss to Vin in the morning and see what happens! Thanks for the heads up!
@
Edit: I was running them with a 300ms pause earlier today to watch the sequence of the LED's. Hard to tell they were moving unless you didn't pay attention to them for a few minutes.
Edit 2: Pushing up to 9.6 volts did the trick. I can run with a 1ms pause and they seem to turn a bit faster.
I modified one of the Stepper motor controllers in the OBEX to test these motors/drivers with a Prop. If anyone is interested let me know and I will zip it up and post it. I have a forward/reverse, forward only and reverse only. I am working on one to work with a pushbutton also.
I'm assuming that those GM steppers 3 posts back are for car instrumentation dials, fuel temp pressure gauges & such. Actually a nice idea since they can hold last position even with power off (good for fuel gauge).
I ordered a few bare motors, thanks to erco's tip about the ULN 2803 IC. I have a couple of differential drive 'bots on the back burner using the steppers.
Here are six GM instrument cluster geared steppers for $16.50, free ship from a US seller, so $2.75 each, lifetime warranty. Maybe Ken should sell a robot with these motors and his "lifetime warranty" PropBoE, as the last robot anyone will ever need to buy!
Pushing Iron :-
Here is another good reason to stock-up on these "puppies"
Been a while since i posted, 3D printer needed full attention.....
I am making a 3D printed actuator and thought for a test i would use the singing-all-dancing 28BYJ-48
Its a wormscrew and wormscrew nut......driven (RSJ style) until the stepper motor couldn't breath in or out .
Result :-
Pushes a static load 2.3 Kgs
Lockout :- 2.8 Kgs
Thats enough to crack an egg dont you think.....
It will be part of this system :-
Good effort, Gareth. I wondered what you were up to, il mio amico! I tore one of these down and was put off how small the internal plastic gears were. They might not last long in a high torque app like thiis. Please advise your findings and Happy Holidays!
Comments
The % signs and some digits in the DATA and DIRL statementswere dropped ?!?!
I corrected the code in post #84 http://forums.parallax.com/showthread.php/141149-3-Stepper-Motor-amp-Board?p=1137217&viewfull=1#post1137217
I looked through here and didnt see much besides erco said the output shaft gives 2000 steps, that seems like a really accurate motor for this price, wouldnt that be .18 degrees per step???
Since seeing his post, I've been on the lookout for these encoders. I've found several in a printer I took apart. I keep meaning to use it to precisely point a laser. I'm not really sure how I'd make this work, but I think it would be interesting to see how precisely these encoders would allow a laser to be aimed.
You might want to keep you eyes open for these sorts of encoders.
Also keep in mind you can increase the positioning resolution of a stepper by gearing it down (though backlash will still be a problem).
If you have a good power supply, you should be able to keep servos from jittering. Your 1 degree estimate seems about right, but theoritecally a servo that turns 90 degrees over a pulse range from 1000us to 2000us could have the resolution of 0.09 degrees. I doubt there are many (if any) servos that could really reach this accuracy but I'd think half a degree should be possible if one had a high quality servo and were very careful with the hardware and software.
This is basically for a DIY laser range finder, using WiiCam. According to Gareth you have to adjust the lasers angle for short or long distance, So the idea is to mount the cam on a platform that rotates 360 degrees, then set the laser next to it, on its own rotating platform, the idea is the wiicam stays fixed while the lasers angle can adjust, wile the hole device rotates 360 degrees. Since one would need to do pretty precise math that involves knowing the exact angle of the laser something that can adjust the laser 1 full degree at a time (at least 1 degree seems resonable, cant think of why you would need more), with no backlash is very much needed, this laser need to be where its suppose to be, weather it got there by a stepper or a dc motor with encoder. Now whatever solution I use to rotate the whole laser/cam assembly in a 360 manner is the one that need to 5 degree or less movements, as this will dictate the max resolution of the laser scanner. These cheapo steppers paired with an absolute encoder may be the ticket, if I understand this right. The encoder can give me my starting angle, then I can keep stepping taking a scan every .18 to .5 degrees, when I hit the place on the encoder telling me ive done a full 360, I stop the laser, then stop the motor. When the motor stops the backlash will happen, but I will already be done scanning, and ill be able to tell its stop angle via the encoder. Does this sound good in theory or am I misunderstanding some of the details?
What I have to work with as far as money, is a $25 dollar ebay gift card, which I also need to buy a better laser, even a 2 dollar laser pointer is an improvement over the ebay laser diodes I currently have, the culminating lens (if thats what it even is) is a joke and my laser blobs to the size of a quarter after 10-15 feet. Im also thinking I want to get IR this time.
So anyways just want to get my ducks in a row and find the right parts to attach to the stingray for later use, there has been to many times I wasted money on either A, junk, such as these laser diodes or B, bought something that doesn't quite fit the bill ex, these micro servos. Ive got most of everything I need for this bot except some type of hi accuracy pan or pan/tilt devices.
Indeed...indeed..... Its a while since i linked my Wii-Camera up..... however new ideas have been brewing in the background :-
(1) Place extra lasers (all at different angles) on the (stepper/servo) mount .... the Wii camera will detect 4 (lasers are cost effective at momo)
If they are set in 4 different plains - then for example ...the top quarter of the Wii camera horizontal array will detect one laser....the 2nd quarter detects second laser ....etcetcetc
This would allow for long, mid-long, mid and short range detect simultaneously....
If you set the horizontal detect to be very narrow then it would be possible to filter out some of the ambient IR noise that can show up.
On an inspirational note :- I am well impressed by the results i gain with my Wii camera..... and even pointing the thing on the floor away from you gave quantitative readings (ie ultrasonic or IR will not do this)
(2) $3 steppers....... (go for it before i do :-)....... I would use 2 back to back Wii cameras and scan just °180
I would then attach a spring to the laser arm and it would pull back on one side to keep deadband always in the Positive (or negative if you know what i mean) with °360 its a tad more difficult.......
Just a few ideas.....
I've decided to get a supply of drivers for 12V unipolars. I'm looking for reliable suppliers and their shipping times. Who are you buying from at the moment?
Now to find a good use for the critters. :-)
Amanda
Edit: Motor only was $2.17. http://www.ebay.com/itm/New-Gear-Stepper-Motor-DC-5V-4-Phase-Step-Motor-Reduction-Step-Motor-For-Arduino-/350554126227?pt=LH_DefaultDomain_0&hash=item519ea77793
Kind of frustrating since the darned thing worked Thursday!
Sorting through everything, trying to understand what was (wasn't) happening, I noticed a small difference in the code. In my original attempts to get the motor running I used the code beginning with:
' {$STAMP BS2} ' {$PBASIC 2.5} 'spins stepper motor about 180 degrees & back 'uses P0-P3 to ULN2003 controller board 'press BoE reset to cycle DIRL=00001111 B0=1On Thursday, I cut and pasted code from this thread, but the variable B0 was defined B0=2. With a value of '2' my motors run (even the ones I thought were dead). I'm not sure why this is. Is a pause of '1' too short for the motors to react?
Anyhow, now I have four functioning steppers (but only two controllers :-< ). Yay!
Amanda
You could make a controller for those motors out of a darlington array* which are a few bucks. Probably any transistor has enough umph because they're only 5 volts and I can't imagine that they use much current. For a bigger unipolar stepper I've used TIP 120 power transistors which would be complete overkill for them.
* See page 2 of this Parallax document:
http://www.parallax.com/Portals/0/Downloads/docs/prod/motors/Stepper_Motor_27964.pdf
Thanks for the info!
@
The delay limit is also different if you are full stepping or half stepping. I would suggest to start slow, and then search a limit.
Massimo
Amanda
Pretty sad that you got 2 bad motors out of the gate. I'm in China right now. I'll make sure the locals hear about this!
Seriously, I have used 12V (3 Li-ions) just fine on 5V motors. Don't be shy with voltage, just careful.
Running them from a BS2 BOE using a 9.6v battery. I'll switch from Vss to Vin in the morning and see what happens! Thanks for the heads up!
@
Edit: I was running them with a 300ms pause earlier today to watch the sequence of the LED's. Hard to tell they were moving unless you didn't pay attention to them for a few minutes.
Edit 2: Pushing up to 9.6 volts did the trick. I can run with a 1ms pause and they seem to turn a bit faster.
http://www.ebay.com/itm/5pcs-Stepper-Motor-Driver-Board-ULN2003-5V-4-phase-5-line-EP98-High-Quality-/111074056103?pt=LH_DefaultDomain_0&hash=item19dc8797a7
@
New tiny size, haven't seen these before. Might have to try!
http://www.ebay.com/itm/10PCS-4-Wire-2-Phase-Miniature-stepper-motor-diameter-6mm-Height-8-5mm-no-1/221258207384?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D163%26meid%3D76812138580520418%26pid%3D100005%26prg%3D1088%26rk%3D2%26rkt%3D4%26sd%3D321170304463%26
http://www.ebay.com/itm/6x-repair-stepper-motor-GM-GMC-speedometer-gauge-kit-instrument-cluster-10-bulbs-/151087837183?pt=Motors_Car_Truck_Parts_Accessories&hash=item232d896fff&vxp=mtr
I've noticed those. What could you use them for?
@
http://www.ebay.com/itm/5V-Stepper-Motor-28BYJ-48-With-Drive-Test-Module-Board-ULN2003-5-Line-4-Phase-/200880153274?pt=LH_DefaultDomain_0&hash=item2ec563e2ba
and the motors alone for $1.87...
http://www.ebay.com/itm/Gear-Stepper-Motor-DC-5V-4-Phase-Step-Motor-Reduction-Step-Motor-for-Arduino-O0-/290975507318?pt=LH_DefaultDomain_0&hash=item43bf7de376
Lastly, a few "used" 12 volt motors for $1.75...
http://www.ebay.com/itm/Special-offer-1x-Used-24BYJ48CH-4-phase-5-wire-Stepper-motor-/151147299618?pt=LH_DefaultDomain_0&hash=item233114c322
I'm assuming that those GM steppers 3 posts back are for car instrumentation dials, fuel temp pressure gauges & such. Actually a nice idea since they can hold last position even with power off (good for fuel gauge).
@
http://www.ebay.com/itm/6X-Stepper-Motor-GM-Chevy-Cluster-Gauge-Speedometer-X25-168-X27-168-Motors-/180826560825?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AGMC&hash=item2a1a1a5939&vxp=mtr
Here is another good reason to stock-up on these "puppies"
Been a while since i posted, 3D printer needed full attention.....
I am making a 3D printed actuator and thought for a test i would use the singing-all-dancing 28BYJ-48
Its a wormscrew and wormscrew nut......driven (RSJ style) until the stepper motor couldn't breath in or out .
Result :-
Pushes a static load 2.3 Kgs
Lockout :- 2.8 Kgs
Thats enough to crack an egg dont you think.....
It will be part of this system :-