Alt-BEAM Archive
Message #10412
To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Fri, 18 Feb 2000 13:47:35 -0800
Subject: [alt-beam] Re: More fun questions
Sathe Dilip wrote:
>
> Using the ohms range of your multimeter, measure the resistance of the
> solenoid coil. Divide the voltage you want to apply by this value in
> ohms.
Is that precisely correct? I vaguely recall from my student days that
there was this messy thing called impedence. It was kind of like a
current through a coil resists itself. Can't remember exactly. That was
the point I decided I wasn't going to be an electrical engineer :)
Anyway, by way of experiment, I tested a small coil with my meter:
Voltage: 4.5
Current: 0.8 amps
Resistance 4.1 Ohms
So 4.5/4.1 = 1.1 amps calculated, versus 0.8 actual. Enough to affect
which type of driver circuit I might use.
Comments?
Bruce
10413 Fri, 18 Feb 2000 13:46:45 -0800 [alt-beam] Re: More fun questions beam@sgiblab.sgi.com Bruce Robinson BUDSCOTT@aol.com wrote:
>
> ... with most of my previous questions about solenoids, people
> said they had a return spring. Mine don't. it's weird, the
> armature came seperated from the core, they just slide in,
> no spring.
Hi, Spencer. As you are beginning to discover, there are probably as
many types of solenoid as there are types of motor.
For the type you have described, the sliding bit will try to center
itself in the magnetic field when you power it up. I've got a couple
like that salvaged from an ancient VCR. One is hollow right through; the
other has a plate across one end. Neither one has an integral spring --
they relied on external linkages and springs to restore them to their
"off" position.
Looks like you'll need to supply your own springs (and ingenuity) to
create a legged robot. An electric drill and a vice are useful, or a
drill press if you have access to one. Try to use springs that are just
powerful enough to restore the moving portion to it's off position.
Don't forget to allow for A) gravity, and B) the weight of anything you
attach.
You can make your own springs using music wire (e.g. guitar strings) and
a wooden core. I use a tiny lathe to turn mine, but lots of people have
made them using nothing more than a wooden pencil.
Regards,
Bruce
10414 Fri, 18 Feb 2000 13:57:00 -0800 [alt-beam] Re: Geared motors...again beam@sgiblab.sgi.com Bruce Robinson Paul Atkinson wrote:
>
> They look like Hankscraft motors (used in moving store displays).
> If I'm right, the data sheet is at:
> http://www.hankscraft-motors.com/dc3440.html
>
> Has else anyone used these yet?
More to the point, does anyone know what they cost?
Bruce
10415 Fri, 18 Feb 2000 13:47:54 -0800 Geared motors...again Bernard Nazari Hey all,
Well, I managed to get my first brain done for my first walker, the only
problem is that I haven't found a motor that will work. I found a couple of
mega-cheap motors at a surplus store, but they have just about enough
torque to turn the gears...that's it. I know I can hack into a servo and do
it that way (and spend $30 on a walker), but I am hoping to not sell my car
to get into this hobby. I'm in the L.A. area, so I'm pretty sure there has
to be something around here. Any ideas? (And I did look at the MECI,
MicroMo, and some other sites, except they don't have the roughly 30RPM@5V
sort of motor that I want.) Anyway, take care and have a good Presidents Day!
content-transfer-encoding: quoted-printable
>
Bernie...do you kno=
w where the =
City of Paramount is? On Paramount Blvd just south (about a block and=
a =
half around the bend) of the 105 on the left hand side there is a surplus =
store. Try in there...they have ALL KINDS of neat toys and stuff... f=
rom =
motors to ammo cans. It's also a good cheap spot for tools. Mos=
t of =
the stuff in there is new...but very cheap. Hope this helps. If=
you =
need better directions...let me know...And if you know of anything BEAM or =
robotics related in the LA/Orange area...let me =
know.
Dane =
Gardner
-----Original Message-----
From: Bernard =
Nazari
Subject: Geared motors...again
Hey =
all,
Well, I managed to get m=
y =
first brain done for my first walker, the only
problem is that I haven't=
=
found a motor that will work. I found a couple of
mega-cheap motors at a=
=
surplus store, but they have just about enough
torque to turn the =
gears...that's it. I know I can hack into a servo and do
it that way (an=
d =
spend $30 on a walker), but I am hoping to not sell my car
to get into t=
his =
hobby. I'm in the L.A. area, so I'm pretty sure there has
to be somethin=
g =
around here. Any ideas? (And I did look at the MECI,
MicroMo, and some o=
ther =
sites, except they don't have the roughly 30RPM@5V
sort of motor that I =
want.) Anyway, take care and have a good Presidents =
Day!
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