Re: DC motor control. auto reversing

On 2006-01-01, Nick Zentena <zentena@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Jasen Betts <jasen@xxxxxxxxxxxxxxxxxx> wrote:
>
>>
>> hmm a black cylindrical thing with a red band and a stepped end.
>>
>> looks a little like a land mine but probably isnt.
>
> No-) Small film tank. Will hold a max of two rolls of film or various
> other combinations.
>
>>
>>> Worse case is 30 minutes of steady turning. It won't be used much just
>>> when I need the smaller drum.
>>
>> I'll assume that's typical... is that slowest or fastest?
>
> I think I didn't explain this right. When I said 30 minutes I meant the
> setup would need to be on and running for 30 minutes at worst. I looked up
> the commerical product that spins the drum. It claims 75rpm. But they also
> require a range of 65rpm to 75rpm for the process. I'm guessing a fully
> loaded large drum slows down thier motor.

At 70rpm the half-cycle of 1.5 turns would take approx 1.3 seconds
so 1.5 turns and 1.5 back would be 2.6 seconds

>> the next problem is the 520 degree turn and then the reversing at the end.
>> and coming back (and then stopping?)
>
> No repeating until the external timer shuts off the power to the motor.

ahh... I'm no mechanical engineer (watch the flames fly) but,
I'd be looking to do an all-mechanical solution

reversing every 1.3 seconds will be hard on most motors, and/or on any
mechanisms light enough to be reversed in that way.

or could you fit the tank inside a tube that would fit on your larger machine?


it sounds like a old washing machine agitator may have the function you want
but on the wrong axis, the speed van be varied if needed by using different
sized pulleys on the motor iirc 1.5 turns is fairly typical and is a little
over 1 second before reversing...

Bye.
Jasen
.

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