Re: Flapping "For Sale" sign, need design help for
mroberds_at_worldnet.att.net
Date: 03/27/05
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Date: Sun, 27 Mar 2005 17:02:23 GMT
casteele95thbgheavy@yahoo.com wrote:
>Windshield wiper motor: ashamed of myself for not thinking of that :)
>Can I run that off a battery smaller than a car battery?
Yes. You could run it off flashlight batteries if you wanted to, but
you'd have to buy a lot of flashlight batteries. If you run it on low
speed (0.91 A at 12 V) for 8 hours, it will take about 7.3 amp-hours
of battery. A 12 V sealed lead-acid "gel cell" battery rated at 9.0
amp-hours or more will weigh around 5 pounds and do the job. The
GC-1214 for $25 at the same place with the wiper motor is a 12 V, 12
amp-hour battery and will work fine.
You have to buy a battery rated more than 7.3 amp-hours, since the
rating assumes that you'll use the battery up over 20 hours. Since
you'll use it up faster than that, you don't get the full rating.
When the battery is discharged, you can charge it back up with a normal
12 V car battery charger. Set it to the lowest current rating you have;
a 2 amp or less charge rate would be best. This is not the right way to
charge a gel-cell if your life depends on it, but for twirling a sign it
will work fine. You need to put a bit more than 7.3 amp-hours back in,
so if you have a 1 amp charger, you need to charge for 8 or 9 hours; a 2
amp charger needs 4 or 5 hours, etc.
Since the current is pretty low, you can put the battery some distance
from the sign where it's out of the way (like, behind a tree, or in the
water meter hole) and run a 16 gauge or so extension cord to the sign.
Even if you put the battery right at the sign, a 5 amp or so fuse in the
battery positive lead is a good idea.
If you have a cheap battery charger rated at 1 amp or more, you can even
skip the gel-cell battery. Put the battery charger in the garage and run
an extension cord from the 12 V clips on the battery charger to the sign.
Put a lamp timer on the 120 V plug of the battery charger and you don't
even have to remember to turn it on. If you have a fancy battery charger,
this won't work, as it wants to see some voltage on the leads to verify
that it's really hooked up to a battery.
If you don't have any battery charger but you still want to skip the
battery, buy a DCTX-1212 wall transfomer for $4.50 at the same place as
the wiper motor. Plug it in in the garage, run an extension cord on the
12 V side to the wiper motor, done.
Matt Roberds
- Next message: Fred: "Re: To fuse equipment or not to?"
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- In reply to: casteele95thbgheavy_at_yahoo.com: "Re: Flapping "For Sale" sign, need design help for"
- Next in thread: Robert Monsen: "Re: Flapping "For Sale" sign, need design help for"
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