Re: Encoders from Wirz

Tim Goldstein wrote:

> From: "Tim Goldstein" <timg@...>
>
> Jon,
>
> If I am following your description correctly you are calculating this based
> upon attaching the encoder to the leadscrew?

Yes, for best accuracy, this is the only way to go.

> Assuming you are using a 4 to 1 reduction to the leadscrew how would this
> work out if you attached the encoders to the motor instead? Seems to me that
> you would then get 9600 counts per inch using your scenario. Would that be
> usable?

No, I wouldn't ever put a cog belt between the screw and the encoders. There
can be cyclical errors in the spacing of the cog teeth on the belts, and it is very
common for the sprocket wheels to be a little off center. this would put all
sorts of odd, cyclical errors in your positioning, and also add a bit of
non-repeatability if you moved 5" away and then came back to the same
coordinate.

As for sources for encoders, I don't know any good ones. You can buy
the 'guts' from HP, I think it is the HEDS 9300 series, 1000 cycles, but
no index. You get an optical read head and an encoder disc. I think it
is about $50-60 for the 2 parts.

Jon