Re: [CAD_CAM_EDM_DRO] Newbie-esque problem

Intellicorp001 wrote:

> Hi All,
>
> I've been lurking around here since July. I've been getting a feel for
> whats available, what I might need & what I can afford. The level of
> expertise on this board is just awesome & I'd like to thank all those who
> generously contribute their time.
>
> I have a teensy problem at the moment & I wonder if I could get some
> advice. I want to record the movement of my motorcycle front forks. I have a
> recording device (pic microprocessor based) and I want to feed it with
> positional information about what the forks are getting up to. I had first
> thought about a slide potentiometer but pricey much? Wow, I'm looking to
> spend $50 not $500. Resolution wise, analog would be overkill, steps of 100
> would be great, steps of 20 would be sufficient.
>
> You guys measure position all the time, admittedly with way more accuracy
> than I want, but can you think of a cheapy, rugged (waterproof would be nice
> to have) way for me to 'read' the position of my forks ?
>
> Sorry this isn't on topic but you don't have a coffee_lounge for off-topic
> posts.
>
> Time is money & money is beer so there's a case of 'the beer of your choice'
> for the best answer.

Slide pots up to about 8" are pretty standard items, available in various
catalogs. Check Marlin P Jones, Mendelson, Alltronics. These are used
as gain pots on sound and light boards. The ones for sound gain are
log taper, but pan pots and lighting board pots are linear. I think, for
relatively short term testing, this would be the easiest way to go.
Another way would be a low-cost shaft encoder and the 'string'
method. You attach the encoder to one part, and a rod to the part
that moves against it. You use a fine steel cable, or even fishing
line, and run it from the moving part, wrap it around a drum on the
encoder shaft, and then tie it to the end of the rod with a spring.
The spring holds the 'string' taut on the drum, and rotates the drum
when the forks move. this could be made pretty weatherproof if you
intend to keep it on the bike for a long time.

Jon