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[DPRG] Re: Pittman motors at Tanner's

Subject: [DPRG] Re: Pittman motors at Tanner's
From: Robert L. Jordan rljordan at airmail.net
Date: Tue Aug 14 08:38:24 CDT 2001


Where do you get the Hammamatsu's for about $6 apiece?

Bob Jordan

-----Original Message-----
>From:	David P. Anderson [SMTP:dpa at io.isem.smu.edu]
Sent:	Monday, August 13, 2001 9:56 PM
To:	Kipton Moravec
Cc:	dprglist at dprg.org
Subject:	Re: [DPRG] Re: Pittman motors at Tanner's

Hi Kip,


I agree about the encoders.  And I think they are necessary for
a suitably "cool" design.

The encoders I was planning on using are home-brew quadrature encoders
made by super-gluing a stiff paper disk (card stock) on the end of the
motor shaft.  Mike Hamilton from Traxxus in Dallas originally suggested
this as a robust attachment that does not load the rotor or require
fine balancing, because the paper is so light weight.  

The disk pattern is printed on a laser printer and read by two out-of-
phase Hammamatsu IR emitter/detector pairs for quadrature signals.
The ones I'm using on SR04 have 12 divisions and generate 1000 hz signal
at full speed.

I was thinking about making a little circuit card that would screw
to the mounting holes in the back of the motor and hold the Hammamatsu's
at the proper spacing.

In other words I think we can fabricate our own encoders if none are 
readily available.  The Hammamatsu's are about $6 apiece so $12 per
motor if you want direction as well as velocity.  If we can find 
commercial quadrature encoders in that price range then that would be 
preferable, I think.


> I already picked my two on the way to the last DPRG meeting.  The new branch
> of the George Bush Toll Road is now open to I-35, and makes the trip to
> Tanners for me much easier.
> The encoder will be the hardest part, there is not much to grab onto in the
> back.
> Kip
> ----- Original Message -----
> From: "David P. Anderson" <dpa at io.isem.smu.edu>
> To: <dprglist at dprg.org>
> Sent: Monday, August 13, 2001 9:08 PM
> Subject: [DPRG] Re: Pittman motors at Tanner's
> > How many do you want?
> >
> > Seems like we should try to buy enough motors so that Ed K. and Kip
> > and Ralph and Rodent and Robert and Clay and Eric (who already has
> > some) and David and David and Jeff and Barry (is that 12 yet?) and
> > Travis and whoever else expressed an interested can have one.  We can
> > probably anytime replicate the rest of the robot but the motors have
> > proven hard to come by.

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