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Unread 05-05-2012, 04:40 PM
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Re: Optical Encoders

When I try to upload the image it says:

Upload Errors

aDSC_0142.jpg:
Attachment in Progress. Can be deleted here.


But I've sat here 5minuets and nothing has happened.
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Unread 05-05-2012, 04:43 PM
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Re: Optical Encoders

Quote:
Originally Posted by Jengles View Post
When I try to upload the image it says:

Upload Errors

aDSC_0142.jpg:
Attachment in Progress. Can be deleted here.


But I've sat here 5minuets and nothing has happened.

How large is the file you are trying to upload.


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Unread 05-05-2012, 04:46 PM
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Re: Optical Encoders

I have to agree with an earlier poster that there isn't a really good spot to mount the optical encoder. However, do you have a sensor that you could use to count the sprocket teeth or chain links as they go by? Hrm ... probably overthinking things...
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Unread 05-05-2012, 04:46 PM
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Re: Optical Encoders

Quote:
Originally Posted by Ether View Post
How large is the file you are trying to upload.


141KB
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Unread 05-05-2012, 04:49 PM
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Re: Optical Encoders

Quote:
Originally Posted by Ether View Post
I don't see a good place to mount the encoder without making changes/additions to the design.

Perhaps you could drill a hole and tap threads into the end of each wheel axle and make an adaptor for the encoder disk.

EDIT: See attached pic
Or you could mount the encoder to the side and drive it with a gear/belt/chain. Not optimal.


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Unread 05-05-2012, 04:59 PM
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Re: Optical Encoders

Quote:
Originally Posted by Jengles View Post
What I know is: the shaft of the gear box is .5in, it is run belt/chain/gear driven etc., and at full speed (but we only go about 35%) it can go up to 3,408 rpm.
If your gearbox is 16:1 and the output shaft is spinning at 3408 rpm, that means your motor is spinning at 54,528 rpm.

An RS775-12 free speed is 7300 rpm, and an RS775-18 free speed is 13,000 rpm.

You numbers don't add up1.


1assuming the pronoun "it" in your post refers to the immediately preceding proper noun, i.e. the gearbox output shaft


Last edited by Ether : 05-05-2012 at 05:01 PM.
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Unread 05-05-2012, 05:09 PM
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Re: Optical Encoders

The Banebot motor-18v (http://banebots.com/p/M7-RS775-18) has a 17040 rpm. After the P60 gearbox with a 16:1 deduction goes on (http://banebots.com/pc/P60K-S7/P60K-44-0007), it has a 1065 rpm. Then the 32 tooth chained to 10 tooth sprocket makes it 3408 rpm.
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Unread 05-05-2012, 05:12 PM
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Re: Optical Encoders

I just found this. http://banebots.com/docs/EN-G0361-KT-Assembly.pdf . Is this the way to go?
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Unread 05-05-2012, 05:21 PM
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Re: Optical Encoders

Quote:
Originally Posted by Jengles View Post
The Banebot motor-18v (http://banebots.com/p/M7-RS775-18) has a 17040 rpm.
When driven at 12 volts, the 775-18 has a nominal free rpm of 13,000 rpm, not 17040. That would put your wheel axle max speed at 2600 rpm, not 3400.

Factor in the loss of efficiency from the geardown/gearup transmission and it's less than that.



Last edited by Ether : 05-05-2012 at 05:26 PM.
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Unread 05-05-2012, 05:24 PM
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Re: Optical Encoders

Quote:
Originally Posted by Jengles View Post
I just found this. http://banebots.com/docs/EN-G0361-KT-Assembly.pdf . Is this the way to go?
Can't tell from the angle of the photo you posted whether or not you have room for that.


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Unread 05-05-2012, 07:14 PM
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Re: Optical Encoders

I would speculate that they do have the room to mount the encoders he linked to. It's mounted to X bar and should be able to slide back an inch or more.

Jengles, those encoders would be a good option. Although less costly options exist, those may require more work to get them installed.

Another consideration: at 128 pulses per revolution, times about 1000 RPM, 128,000 pulses per minute is a lot of data. In software, there is a way to count only every "Nth" pulse (like every 8th pulse for example) that will allow your software to not have to spend all its time counting pulses. Have your programmers look into how that's done, as they'll need to learn how eventually....
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Unread 05-05-2012, 07:24 PM
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Re: Optical Encoders

Quote:
Originally Posted by DonRotolo View Post
Another consideration: at 128 pulses per revolution, times about 1000 RPM, 128,000 pulses per minute is a lot of data. In software, there is a way to count only every "Nth" pulse (like every 8th pulse for example) that will allow your software to not have to spend all its time counting pulses. Have your programmers look into how that's done, as they'll need to learn how eventually....
If he plugs the encoder into the DSC, the pulses are read in hardware by the FPGA. 128,000 pulses per minute is only 2133 pulses/sec. The FPGA can easily handle that. Then his software just asks the FPGA for the count whenever it wants a reading.



Last edited by Ether : 05-05-2012 at 07:26 PM.
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Unread 05-10-2012, 07:48 PM
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Question Re: Optical Encoders

Hi,
I am looking into a similar option for my team involving encoders. We tried to implement some during build season but due to mechanical inaccuracies, we couldn't get them to fit on and read correctly. (We don't have a machine shop and use hand tools to make all our parts in house.)

The banebots encoders that go on the gearbox would fit in nicely with our system, but I was wondering if they would provide an accurate enough reading for wheel speeds being attached to the gearbox rather than the axle. We have a similar setup with live axles, and chained banebots motors with attached gearboxes.

We would use the encoders to vary the wheels speeds automatically. We already have a camera set up for alignment. I'm just wondering if the speed read at the gearbox can be used in the code with some adjustments for friction losses accurately. I don't do programming so I can't answer a lot of questions personally on how we wrote the code for the set up we tired to implement earlier.

Thanks!
-Anna
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Unread 05-11-2012, 07:53 AM
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Re: Optical Encoders

I had something similar happen, where I wasn't allowed to upload attachments. If you contact the CD staff they can assist. (I think it has something to do with rampant spam-botting.)

Anyway, here's what ours look like.
Attached Thumbnails
Click image for larger version

Name:	encoder mounts.jpg
Views:	56
Size:	81.2 KB
ID:	12750  
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