No argument here, but you still have to have zero and full-range limit
indicators, or "stops". A shaft encoder (or just counting motor steps,
which is what I would probably do) gives you relative position, but
generally not absolute.
Unless, of course, someone begets a better mousetrap - which is why I
posted the question here. :-)
Thanks,
--jim
Jim Barber, N7CXI
On 8/8/2011 1:57 PM, Al Kozakiewicz wrote:
> I'm a digital kind of guy. I think the combination of an optical shaft
> encoder and a microcontroller (PIC, Arduino, whatever) to handle the various
> control tasks would give you a lot of flexibility without resorting to a lot
> of the control implementation in hardware.
>
> Al
> AB2ZY
> ________________________________________
> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
> Jeff Blaine [keepwalking188@yahoo.com]
> Sent: Monday, August 08, 2011 4:22 PM
> To: audioguy@q.com; Amps@contesting.com
> Subject: Re: [Amps] "Best" limit indicators for multi-turn, shaft-driven
> gadgetry
>
> Jim,
>
> I don't have an answer for your actual question. But the pot idea is good
> for another reason. In that would open the door to an
> auto-tune kind of option (or at least, the ability to record presets which
> via the ADC input, could be used to set the cap via the
> stepper). If your drive and antenna loads are stable, that would be very
> cool and not too complicated to code up.
>
> 73, Jeff ACØC
> www.ac0c.com
>
> -----Original Message-----
> From: Jim Barber
> Sent: Sunday, August 07, 2011 4:45 PM
> To: Amps@contesting.com
> Subject: [Amps] "Best" limit indicators for multi-turn, shaft-driven gadgetry
>
> I've reached the point where I need to decide whether or not to make my
> YC156 project amp "remote". Because of other interests, I already have a
> good selection of larger stepper motors and drive electronics, and a
> good feel for how to put it all together.
>
> What I don't have is a good, simple limit stop/reference concept for the
> vacuum caps and (possibly) roller inductor. I've used drive screws and
> leaf switches in the past, but don't like the mechanical sloppiness and
> complexity. I've also seen optical interruptors used in place of the
> leaf switches, but still don't like the mechanical complexity of the
> whole drive screw, platform and guide assembly.
>
> My favorite candidate at the moment is a high-quality 10-turn pot in the
> timing belt path for each shaft, "gearing it down" so that (for example)
> a vacuum cap that rotates 13 turns end-to-end would run 8 or 9 turns at
> the pot shaft. Using regulated 5VDC, I could then apply the output of
> the (pot) divider to a 10-bit ADC. Note I already have ten 10-bit ADC
> inputs at each control processor, so that isn't as much of a
> complication as it might seem.
>
> Any thoughts or suggestions?
>
> Thanks,
> Jim N7CXI
>
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