Encoder suggestion

Gateway off Kearny Villa has some small timing belts and matching
pulleys that might work. You'll probably have to drill out the hubs of
the pulleys and use some epoxy to keep things on. Most pots have a 1/4"
shaft, so you should be set there.

Murphy's in El Cajon (Johnston, NORTH of Main Street -- thanks, John!
<g>) also has a decent selection of pulleys and various sizes of small
timing belts pulled off equipment.

-- Gordon

Hi Padu:
How are you ?
What are you building these days ?
I solved a similar solution with a lathe.
I bought some aluminum knobs with a quarter inch shaft hole.
I put the knobs on my lathe and turned them down to a 0.5 inch size.
Since the rotaional velocity is not too great you don't need it to be
highly balenced.
I would recomend getting a 1 inch  diameter or larget dowel ( maple or
aluminum ) cut a 1 inch lenght , then drill a 1/4 hole all the way
through it.
Then lathe the hole up to the 3/4 diameter.
You can also do all of this on a drill press, although its tough to
get lots of precision.

Come on by to the SDRS meeting this weeked if you can

Thanks
Steve V


wrote:

and matching

"Steve in San Marcos"

Hi Steve! Long time huh?
I'm automating a gasoline ATV. I (thought I had) finished automating the
steering wheel, using an optical encoder on the output shaft of the
gearmotor. Turns out that using a relative encoder for that purpose is not
that practical.


That's what I've been thinking.

I think I found a good sensor for this application:
http://www.beiduncan.com/html/news/nr_9900.htm
It costs about $60 bucks and seems very robust and protected from the
elements. I believe a simple pot (contact) would start giving me headaches
later on. This is a Hall effect sensor, so there is no wear from friction.

Its input shaft is a 1/4" I believe, so what I will end up doing is cutting
the top of the ATV's steering shaft and fabricate a piece of cylindrical
aluminum that fits snugly inside the shaft and hold it with one or two
screws. Then I'll drill a hole that will match the encoder's shaft. Similar
to what you did above.


I'll try. If I had a trailler I could even tow the thing up there. Maybe in
the future.


Cheers

Padu

    For a large diameter shaft like that, a through-hole angle sensor is useful.
These are used as steering shaft position sensors on cars.  Some
are multi-turn devices, and many have both an encoder and a pot.

    We used two of those on our DARPA Grand Challenge vehicle.
The pot was used at startup, and thereafter we read the encoder.
Only 1 degree resolution on the encoder, though.

                John Nagle

"John Nagle"

Yes, that's one way the motor controller documentation (roboteq) suggests.
See my reply to Steve to see what I am planning on doing.

BTW... plans for the new challenge?

Cheers

Padu