Re: DC motor control. auto reversing

Jasen Betts <jasen@xxxxxxxxxxxxxxxxxx> wrote:

>
> yeah, but how many watts (or (fdractional)horsepower etc) do you need
> from the motor. (you need to describe the task in more detail)

Hi,

I need to spin this:


http://www.jobo.com/jobolab/produkte/images/2523.jpg

It's 5" or maybe 6".

My current setup can't handle something that short. The current roller is
rated at 120V 0.15 amps and can easily handle a larger load then the drum in
that picture. That's what 18 watts. The difference is the bigger setup turns
two rubber wheels that the big drum sits on. The gap between the wheels is
too big for a small drum. I'm likely going to try and drive the short drum
using the magnet fitted to it's base.


>
> are you lifting the 1Kg (safest to design for the worst case) weight up
> a great height, or just moving it a few milimetres to the left?

Just spinning it then reversing direction.

>
> if the motor has to stop and start for some of the time it's not moving at a
> constant speed.
>
> how constant do you need the speed to be, cheap tape players typically
> manage 0.5% variation (IIRC) would that be sufficient?
>

I'd bet even a 10% variation wouldn't be a deal breaker. It might actually
help by introducing some random action into the process. OTOH I'd like
something that wasn't too random -)

> what sort of time frame is involved. do you want it to turn at a rate of 45
> degrees per month for half a year and then reverse and turn 45 degrees per
> month in the other direction for the other half of the year? or is this
> something that must be done in less than one second?


Worse case is 30 minutes of steady turning. It won't be used much just
when I need the smaller drum.


Thanks.
Nick
--
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