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Posted by E. Lee Dickinson on September 2, 2006, 1:21 pm
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I have in my mind a concept for a piece of theatrical scenery which needs to
fly up and down about 30', and be positioned repeatably to the resolution of
about 1".
The piece weighs less than 30 pounds, so 1 to 2hp AC servomotor with a
single phase 120v power/speed control would be perfect. (I'd settle for
single phase 240, but would really prefer to avoid three phase power.)
Ideally, it has a few ways to specifiy commands:
1) Go to a position at a certain speed.
2) Spool at a certain speed.
I could build this pretty easy with a DC motor, H-Bridge, and optical
encoder. But for once, I'd prefer to spend the money on an off-the-shelf
solution.
So: Anyone have a line on an AC servomotor and drive that would be suitable,
around (or under!) $1,000?
PART 2:
Anyone have a good source for slip rings? I need to send 12vdc (and maybe
video, if I have my way) down the winch, too.
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Posted by on September 2, 2006, 10:03 pm
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E. Lee Dickinson wrote:
> I have in my mind a concept for a piece of theatrical scenery which needs to
> fly up and down about 30', and be positioned repeatably to the resolution of
> about 1".
I know this is probably out of the ballpark, but how about a garage
door opener? You could use a rotary limit switch instead of the
standard kind on a garage door. I googled for one, and came up with
this http://www.peteralbrecht.com/limitswitch.asp which would provide
around 1/2" accuracy if used with a 6" diameter drum.
I don't actually know that much about garage door openers. Home Depot
seems to be limited to 3/4hp max. Perhaps commercial units are
available which have more power.
Some boast about having quiet operation, and having "soft start", but
of course that is all relative.
Joe Dunfee
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Posted by John Nagle on September 2, 2006, 11:45 pm
Please log in for more thread options E. Lee Dickinson wrote:
> I have in my mind a concept for a piece of theatrical scenery which needs to
> fly up and down about 30', and be positioned repeatably to the resolution of
> about 1".
> The piece weighs less than 30 pounds,
Here's a good intro to stage rigging with powered winches:
http://www.branament.com/flying.php
Another article on safety issues:
http://crpit.com/confpapers/CRPITV15Bauer.pdf#search=%22theater%20winch%20programmable%22
There are commercial products for this sort of thing.
John Nagle
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Posted by Duncan Wood on September 3, 2006, 7:30 am
Please log in for more thread options On Sat, 02 Sep 2006 18:21:52 +0100, E. Lee Dickinson
> I have in my mind a concept for a piece of theatrical scenery which
> needs to
> fly up and down about 30', and be positioned repeatably to the
> resolution of
> about 1".
>
> The piece weighs less than 30 pounds, so 1 to 2hp AC servomotor with a
> single phase 120v power/speed control would be perfect. (I'd settle for
> single phase 240, but would really prefer to avoid three phase power.)
> Ideally, it has a few ways to specifiy commands:
>
>
> 1) Go to a position at a certain speed.
> 2) Spool at a certain speed.
>
> I could build this pretty easy with a DC motor, H-Bridge, and optical
> encoder. But for once, I'd prefer to spend the money on an off-the-shelf
> solution.
>
> So: Anyone have a line on an AC servomotor and drive that would be
> suitable,
> around (or under!) $1,000?
>
> PART 2:
>
> Anyone have a good source for slip rings? I need to send 12vdc (and maybe
> video, if I have my way) down the winch, too.
>
>
IF you're buying a commercial winch, limit switches, an inverter &
standard ac motor will be about half the price. If you want to send video
& power down as well then you'll need one with two winch drums & coil the
cable round the second drum, at which point it may well be far cheaper to
rig a pulley travelling horizontally to take up the slack.
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Posted by E. Lee Dickinson on September 3, 2006, 6:35 pm
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> IF you're buying a commercial winch, limit switches, an inverter &
> standard ac motor will be about half the price. If you want to send video
> & power down as well then you'll need one with two winch drums & coil the
> cable round the second drum, at which point it may well be far cheaper to
> rig a pulley travelling horizontally to take up the slack.
I should have been a bit more specific about the motion. It needs not only
to go to a commanded location, but go to a NUMBER of commanded locations.
Anywhere along its travel. So I definately need the encoder that's part of
servo systesm.
The other additional item I would probably need with an AC motor is a brake,
which I can also spec as part of a servo.
I've found what seems like the right solutions at www.automationdirect.com,
which has to be the only industrial supply store in the world which lists
prices on the internet. It's going to be expensive.. probably around $1500
to $2000 for all the parts I'll need. But it's going to be a permanent piece
of kit, and I've been wanting to get into some good scenic automation stuff
for a while, now.
We'll see!
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> fly up and down about 30', and be positioned repeatably to the resolution of
> about 1".