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Author Topic: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?  (Read 23148 times)

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Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #20 on: May 04, 2010, 07:32:39 AM »
I am afraid this is not correct as there are always 3 signals and they are equally spread along the 360 degrees of one revolution, meaning there would always be a 120 degrees phase shift between them.

Yes thinking about it thats correct, will have to look into it when I get a chance.
The commutation signals are only used at startup as far as I am aware so once the motor is moving they are not used, some of the S type motors (similar to H) had hall signals rather than encoders with commutation tracks, again will have to read up on that.
 I remember reading an article a few years back which showed the difference between BLDC and AC drives and it had some nice animated graphics showing how the poles were energised in either case, will have to see if I can find it again.

Going back to your motor, IF the Ultra 5000's support Self Sensing as the Ultra 3000's do,  then even one of the cheap encoders from US Digital should work for you. You probably would need to make a line driver as well, but no big deal in doing that :)
Hood

« Last Edit: May 04, 2010, 07:34:18 AM by Hood »

Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #21 on: May 04, 2010, 07:41:17 AM »
Have  a look at this http://www.renco.com/uploads/media/106803_113.pdf
There are 4 tracks for commutation on that disc but whether its 8 pole or 4 pole I am not sure, back to work now and tonight I will try and do some reading, unless someone chimes in and saves me the bother ;)

Hood

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #22 on: May 04, 2010, 07:58:59 AM »
Ha.. ha.. This is the exact same paper you once showed me ;) I don't know, still think the number of poles should make no difference.

Yes, as I've mentioned in the previous post the Ultra 5000 does support self sensing as per the manual, so using a US digital encoder sounds like a good  solution. But what do you mean by a line driver?

Daniel

Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #23 on: May 04, 2010, 08:48:48 AM »
Ha.. ha.. This is the exact same paper you once showed me ;) I don't know, still think the number of poles should make no difference.


I can assure you it does,a few years ago  I tried to fit an encoder from a H series motor (6 pole) To a 1326 motor(4 pole) and it didnt work very welll ;D


Yes, as I've mentioned in the previous post the Ultra 5000 does support self sensing as per the manual, so using a US digital encoder sounds like a good  solution. But what do you mean by a line driver?

Daniel


Line driver is to turn the single ended outputs of the US Digital encoder into Differential outputs. In fact I think US Digital sell them for under $10 so probably just as well buying from them. I made up my own for the Step/Dir outputs as I wanted it to plug  directly into the BOB  eliminating wires.

Hood

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #24 on: May 04, 2010, 08:52:21 AM »
Ah... I see. Saw, they also have encoders with differential outputs already. But the speed seems to be the problem with these. Also, most of their encoders don't have an Index channel.

Daniel

Offline Hood

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #25 on: May 04, 2010, 11:05:12 AM »
Ah yes, forgot about the turbo speed :(  Just have to keep an eye out on eBay and check the specs if anything comes up.

Hood

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #26 on: May 04, 2010, 11:19:30 AM »
Here are some good resources I've found on feedback devices:

1. This one explains about Sin/Cos encoders operation:

http://www.sensorsmag.com/sensors/position-presence-proximity/understanding-integrated-hall-effect-rotary-encoders-1254?page_id=1

Apparently this type of encoders is not optical but they rather use hall sensors. As can be seen the resulting Sin/Cos signals have 90 degrees phase shift and their magnitude is not dependant on the shaft angle. This is why a servo drive that can use Sin/Cos encoder, can't use a resolver instead.

2. A very good document explaining resolvers operation:

http://www.admotec.com/TT02.pdf

3. Another one on resolvers:

http://www.amci.com/tutorials/tutorials-what-is-resolver.asp

4. This one covers several feedback devices and has some good information about resolvers:

http://www.motor-solutions.com/datasheets/servo_motor_feedback_devices.pdf

5. Another one on various feedback devices:

http://www.allegromicro.com/en/Products/Design/compumot/a39a44.pdf



So looks like I'll have to replace the resolver with an encoder if I want to use the motor with the Ultra 5000 drive.

Daniel

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #27 on: May 04, 2010, 11:28:32 AM »
Ah yes, forgot about the turbo speed :(  Just have to keep an eye out on eBay and check the specs if anything comes up.

Hood

Yep... guess that is what I'll have to do. The speed seems to be the biggest problem.

Daniel
Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #28 on: May 04, 2010, 12:26:19 PM »
The typical resolver has 3 windings, one is for exciting the rotor and the other two detect the sin/cos signal, the biggest problem with mixing drive is that the excitation frequency and magnitude is different between makes.
The output is two sine waves 90deg apart.
Older types had a permanent magnet rotor.
The Renco commutation encoders have 3 tracks and have to be matched to the pole count of the motor, Renco end theirs with a /x the x being the pole count in pairs, IOW /4 would be for a 8 pole motor.
When fitting one of these encoders the proper track has to be aligned with the appropriate pole, this is usually done with a double beam scope.
Here is a animated link that explains BLDC.
http://users.tinyworld.co.uk/flecc/4-pole-bldc-motor031102.swf
Nosmo.

Offline Dan13

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Re: Allen Bradley Ultra5000 Sin/Cos Encoder? Resolver?
« Reply #29 on: May 04, 2010, 12:48:17 PM »
Thanks Nosmo. Still can't see what would be the difference between a commutating encoder designed for an 8 pole motor and a one designed for a 6 pole motor, for instance?

Daniel