stepper motor encoder wheel

Bits

I am looking for a stepper motor encoder wheel that can measure at most .001" and I need it to mount on the shaft side of the stepper motor. Is there such a device?

jmg

entering optical encoder into Digikey, gives 1,325 choices

idbruce

Hi Ya Bits

Here is a good link for you to all kinds of encoders.

http://www.usdigital.com/

Bruce

Phil Pilgrim (PhiPi)

Bits wrote:

I am looking for a stepper motor encoder wheel that can measure at most .001"

To get a full answer to this question, you need to provide the distance that your translation stage moves per revolution of the stepper motor.

-Phil

GordonMcComb

Bits wrote: »

encoder wheel that can measure at most .001"

For an encoder mounted on the stepper shaft you want to be looking at the angular resolution of the motor, and that will depending on the motor and its drive. If it's a 1.8 degree motor, driven in full steps, then the encoder need not have a resolution greater than that. Half-stepping and micro-stepping will need higher resolutions. Note that with steppers you often don't need high resolutions for the encoder (depending on the application of course), especially if you have an encoder with an indexing feature. You can use the index to determine if the motor steps are no longer in sync with what you've sent it.

The best resource for affordable motor-mounted encoders is U.S. Digital. They have kits and adapters that work with most motors. Steppers with dual-ended shafts are of course easier to work with, but if yours is single-ended only, depending on the space available you might be able to get something in there.

-- Gordon

idbruce

Bits

I agree with Gordon. If the 0.001" measurement is meant to determine linear travel of some sort, then you should consider a linear encoder. However, if you are referring to travel within a given circumference, the resolution of the stepper motor in combination with the stepper motor drive must be taken into account, and mathematically applied to the circumferance of your motor attachment.

Bruce

idbruce

Additionally, if the 0.001" measurement is meant to determine linear travel, you can also determine linear travel by the resolution of stepper/drive combination and applying it mathematically to the pitch of the leadscrew.

vanmunch

GordonMcComb wrote: »

For an encoder mounted on the stepper shaft you want to be looking at the angular resolution of the motor, and that will depending on the motor and its drive. If it's a 1.8 degree motor, driven in full steps, then the encoder need not have a resolution greater than that. Half-stepping and micro-stepping will need higher resolutions. Note that with steppers you often don't need high resolutions for the encoder (depending on the application of course), especially if you have an encoder with an indexing feature. You can use the index to determine if the motor steps are no longer in sync with what you've sent it.

The best resource for affordable motor-mounted encoders is U.S. Digital. They have kits and adapters that work with most motors. Steppers with dual-ended shafts are of course easier to work with, but if yours is single-ended only, depending on the space available you might be able to get something in there.

-- Gordon

I've been looking at encoders for a little bit for a project that I think needs a "professional" encoder (resolution ~500-1,000 per revolution) and I was wondering how I could have my prop read the input from something like this one:
http://www.usdigital.com/assets/general/149_em1_datasheet_0.pdf

Is it really just as simple as having the prop set a pin to input and count the number of times it goes high in "X" time? Thanks!

Dave

idbruce

vanmunch

Is it really just as simple as having the prop set a pin to input and count the number of times it goes high in "X" time? Thanks!

That all depends. In your particular example of the EM1, well that module has three outputs, which would require 3 pins. Basically you would need more than one pin to establish direction of rotation and steps for a particular direction. There is a lot of information on their website pertaining to encoders, which is definitely worth reading. I personally never use encoders, but I have read a lot of their information, which is definitely interesting and informative. Their information is definitely worth reading if you are truly interested in encoders and the use of encoders.

Bruce

vanmunch

idbruce wrote: »

vanmunch



That all depends. In your particular example of the EM1, well that module has three outputs, which would require 3 pins. Basically you would need more than one pin to establish direction of rotation and steps for a particular direction. There is a lot of information on their website pertaining to encoders, which is definitely worth reading. I personally never use encoders, but I have read a lot of their information, which is definitely interesting and informative. Their information is definitely worth reading if you are truly interested in encoders and the use of encoders.

Bruce

Thanks Bruce, I'll do that.

Duane Degn

I was positively impressed with AustriaMicroSystem's AS5055 magnetic encoders. They give 12-bit (0 to 4,095) resolution within in a revolution. I'd think as long as these encoders where read from at least once during a revolution, they could also be used to keep track of how many revolutions have been made as well as the motor's position within the present rotation.

I'm planning on making a couple of different little boards for these chips within the next month. They work best if a magnet can be attached directly to one end of the rotating shaft.

I'm looking forward to making some super servos with them. I'd think they'd be a good option for obtaining rotational information from a stepper.

Just another option to consider when thinking of encoders.

T Chap

http://www.usdigital.com/products/encoders/incremental/rotary/kit/e2

You can contact US Digital tech dept to get the right part number including type of mounting plate, cover, shaft diameter, etc. They are very helpful. Find out the shaft diameter before calling. Regarding the .001, you need to clarify what that is relative to. If linear motion on a lead screw, then you can calculate linear distance by revolutions of the shaft when you have a known value of distance = X revolutions. For example, if using a 20TPI lead screw, then you have 1" of travel = 20 revolutions. If the encoder is outputting 1600 counts per revolution, then the total distance of 1" will have a count in the quadrature encoder object of 1600 * 20(revolutions) or 32000. If you divide 1" by 32000 then you get a resolution of .00003125" per encoder count. But, since the stepper probably only moves in whole steps at 200 steps per revolution, then the steps of the stepper becomes a factor to consider. If the the stepper is 200 steps per rev, then each step then becomes 1600(encoder res) / 200 = 8. So that each step is 8 * .00003125" = .00025" per step. Another way to look at this, is .00025 * 200steps = .05" of travel of the object attached to the 20TPI lead screw. To take it further, 20 revolutions( based on a 20TPI lead screws) * .05" = 1" of travel, or 20 * 200 steps of the encoder equaling 4000 steps = 1" at whole steps. If the stepper driver is at 1/2 or greater steps, then you multiply the resolution.


With the E2 encoder, you just need the A and B outputs to the Prop and the quadrature encoder object. Provide 5v to the encoder but use a 1k series resistor on the A and B outputs to the Prop.

vanmunch

T Chap wrote: »

http://www.usdigital.com/products/encoders/incremental/rotary/kit/e2


With the E2 encoder, you just need the A and B outputs to the Prop and the quadrature encoder object. Provide 5v to the encoder but use a 1k series resistor on the A and B outputs to the Prop.

Which encoder object would you recommend for the E2? (I ordered a few of them and I can vouch for their friendly customer service.)

http://obex.parallax.com/objects/24/
or
http://obex.parallax.com/objects/544/
or a different one?

Dave

[Thanks bits for not minding me asking this in your thread]

T Chap

I only use the Quadrature Object. I have never used the Dual version and did not know it existed until just now. If you are driving one motor, then the first is fine, but if two motors with encoders, it will save you a cog to use the Dual.