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Electronics => Electronics => Topic started by: dacb on March 11, 2011, 01:18:34 PM

Title: optical interrupt encoder on roller chain?
Post by: dacb on March 11, 2011, 01:18:34 PM

I'm wondering if anyone has any experience or thoughts on a roller chain based optical interrupt encoder.  Imagine a motor that drives a wheel using standard roller chain, e.g. #25, 1/4 pitch.  The open space in the links of the chain transmit the light and the pins in the chain block it resulting in a pulsed encoder signal.

I can imagine a problem related to chain tension that might result in the chain contacting the transmitter or the receiver, but that should be surmountable by placement and design.

Thanks!

Title: Re: optical interrupt encoder on roller chain?
Post by: vinniewryan on March 11, 2011, 03:35:28 PM

The best way to ensure the chain will not come in contact with the encoder is to use a laser diode with plenty of distance from the chain as your light source.

Title: Re: optical interrupt encoder on roller chain?
Post by: Soeren on March 12, 2011, 12:37:45 AM

Hi,

Quote from: dacb on March 11, 2011, 01:18:34 PM

[...] Imagine a motor that drives a wheel using standard roller chain, e.g. #25, 1/4 pitch.  The open space in the links of the chain transmit the light and the pins in the chain block it resulting in a pulsed encoder signal.

Imagining... Resolution = Wheel diameter x Pi / number of cogs.

Besides, it would be just as easy to just measure the cog wheel, either optic or eg. by a Hall element.

Quote from: dacb on March 11, 2011, 01:18:34 PM

I can imagine a problem related to chain tension that might result in the chain contacting the transmitter or the receiver, but that should be surmountable by placement and design.

Yes, a dual pulley chain tensioner, with the optic components mounted in between the two pulleys - no slack there... But why bother, there's better ways to get low-res odometry?