[dorkbotpdx-blabber] where to get and learn about solenoids
Greg Borenstein
I want to acquire some solenoids and learn about how to use them in
projects. Specifically, I want to turn my drum playing robot (http://www.youtube.com/watch?v=JevNR-CZz5I
) over to solenoids. I'm also interested in their uses in animatronics.
I was wondering if anybody had any advice on which models of solenoid
would be good to start with, where to get them, and things I could
read to learn about how to use them.
Thanks,
Greg
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Mr.T
and here's a bunch online:
http://www.allelectronics.com/make-a-store/category/575/Solenoids/1.html
or
http://www.goldmine-elec-products.com/products.asp?dept=1178
-eric
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Mr.T
http://www.surpluscenter.com/sort.asp?UID=2008120222425874&catname=electric&keyword=ERSO
http://www.surplussales.com/Relays/RESoleOF-1.html
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On Tue, 2 Dec 2008, Greg Borenstein wrote:
Donald Delmar Davis
Hey all,
I want to acquire some solenoids and learn about how to use them in projects. Specifically, I want to turn my drum playing robot (http://www.youtube.com/watch?v=JevNR-CZz5I) over to solenoids. I'm also interested in their uses in animatronics.
Greg Grunest
Solenoids come in all different varieties. Typically, you find the 12 V,
linear, push or pull solenoids in everyday consumer electronics (disk
drives, hard drives, tape players, that old and now useless Zip-100 drive
has a really cool 6v one in it but it's *really* hard to get it out, etc...)
but every so often you can find surplus rotary solenoids too. For moving
the drumsticks, a rotary solenoid might be the thing. They typically move
through a 90 degree arc when energized and then return to where they started
when power is removed. However I've had some before that sort of ratchet
through 15-30 degree increments each time power is applied eventually
spinning all the way around. They were connected to a little mechanical
counter and appeared to do nothing more than count how many times this thing
had fired.
The pros:
They're cool!
They typically work forever - millions of cycles.
You can do things with an $8.00 solenoid that you could otherwise
spend hundreds of dollars trying to replicate. (I once built a remote
controlled golf cart and used Ford starter solenoids ($8.00 from Napa) to
switch the 600 Amp battery connections to the motor. I used a $3
optoisolator to drive the solenoids and an 8051 to drive the optoisolator.
Controlling 600Amps from a microprocessor for $11 - Woot!)
You can get feedback from them by measuring how much current they
draw (voltage drop across an in-line resistor) and tell if they are hitting
anything. They tend to draw a lot of current (like a stalled electric
motor) if you hold them against their will.
The cons:
They suck current like mad and therefore are not good for battery
driven applications.
It's basically a coil so you have to worry about re-induction when
the magnetic field around the coil collapses so you don't blow up sensitive
circuitry (like the Arduino or a transistor).
They are typically not driven by any control signal that is easy to
generate in a microprocessor world, 9-50V, 500ma-2A.
(Because of these two drawbacks, I highly recommend a simple 8 pin
optoisolator to drive them. It's cheap and completely protects the
Arduino.)
You can't control how fast they move like you can with a servo.
They are either in or out, turned or not. In fact, if you try to slow them
down by limiting the voltage they draw a LOT of current.
They are entirely digital - On or off, in or out.
And the number one drawback is........ can you say "latch up"?
(sometimes they stick in the "energized" state.)
Just my 2 cents.
BTW: If you're interested, I think I have a couple of the 90 degree rotary
ones left. Enough for you to play with and try the drums anyway.
- Greg Grunest
gr...@grunest.com
Greg Borenstein
Maybe sometime I'll come to a meeting and you can explain some of that
to me! Looking forward to the video...
-- Greg
On Dec 2, 2008, at 8:51 PM, Donald Delmar Davis wrote:
> Greg,
>
> I am testing a set of 12 volt solenoids that I bought at surplus
> gizmos after our previous email exchange.
>
> I plan to use the spare board from the unipolar stepper drivers for
> the bike meter project since each coil of a unipolar stepper motor
> looks like a solenoid to transistor man.
>
> <pastedGraphic.tiff>
Greg Borenstein
That was really helpful! I'd love to take you up on that offer for the
rotary solenoids if you've still got them. Any leads on where I can
look to learn more about "opto isolators"?
-- Greg
Greg Grunest
An opto isolator looks like a led and a phototransistor in the same sealed
package. You drive the LED from one of the Arduino ports, just like you do
for the built-in pin 13 LED. Turn it on, turn it off, etc... The
phototransistor "sees" the light emitted from the LED and turns itself on
and off in turn, acting like a switch. You can switch much larger currents
and different supply voltages with the phototransistor this way. It's
called an optoisolator because at that point, the two sides of the circuit
(the LED side, and the phototransistor side) are "optically isolated". It's
cool because you can have massive (not really too massive) voltage spikes
and current draws on the phototransistor side of the circuit and the
microprocessor, sitting on the LED side, will never even know it's going on.
Another cool thing I forgot to mention is that it's a super easy way to
allow a microprocessor to control line voltage. You can switch 120V AC with
this device. BE WARNED THOUGH!! Messing with 120V AC can and will hurt
you. It *WILL* blow up your Arduino. It *WILL* eventually send you flying
across the room and lighting your underwear on fire.
Don used one on his most recent music board for the Arduino in the cult
induction class. I didn't look at what it was or where he got it from but
he might be a good person to ask.
- Greg Grunest
Paul Stoffregen
a clamping diode connected in parallel with the solenoid. The cathode
(side with the stripe or other marking) goes to the positive side and
the anode goes to the negative side. Schottky or "fast" diodes are best.
If you forget the diode, the solenoid makes a high voltage spike that
will usually destroy the transistor and maybe your microcontroller too.
Many solenoids are designed for AC voltage (usually 24 volts), but you
can drive them with DC if you use a lower voltage (usually 1/2 or less
of the rated AC voltage). If the coil gets scorching hot, that's a
pretty good sign you need to lower the voltage. If you experiment with
a variable power supply to find the minimum necessary voltage, be sure
to do it with the mechanical load connected.
If you use an optoisolator to switch AC (triac output), unless you
really know what you're doing, it's much easier if you get one that has
a "zero crossing" feature.
douglas repetto
FWIW, I have a website that I teach lots of workshops from that covers
the basics of different kinds of motors/solenoids/relays/etc. By basics
I mean basics, but with the goal of providing the vocabulary so that you
can go out and do web searches for more specific info once you actually
know what you want to learn about. It's here:
http://music.columbia.edu/~douglas/classes/motor_mania/
best,
douglas
--
............................................... http://artbots.org
.....douglas.....irving........................ http://dorkbot.org
.......................... http://music.columbia.edu/cmc/music-dsp
.......... repetto............. http://music.columbia.edu/organism
............................... http://music.columbia.edu/~douglas
John Brown
If I may ask a quick question, though, does a solenoid work is the
same way as a coil gun, in that the induction of current into the wire
draws in the metal shaft? Is that what gives it the binary action? And
then when current is stopped, what pulls the shaft back out of the
coil?
I hope I am understanding it correctly.
-John Brown
Greg Grunest
(coil) pushes (or pulls) the shaft, a spring returns it to the original
position when the coil is deenergized.
On a rotary solenoid, it's usually a spring and some gears and a little cam
type device.
- Greg
-----Original Message-----
From: dorkbotpdx-bl...@dorkbot.org
[mailto:dorkbotpdx-bl...@dorkbot.org] On Behalf Of John Brown
Sent: Wednesday, December 03, 2008 12:26 PM
To: A discussion list for dorkbot-pdx (portland, or)
Subject: Re: [dorkbotpdx-blabber] where to get and learn about solenoids
douglas repetto
Right, it works as an electromagnet. But it's not really a binary
action, in that it doesn't pull one direction and then the other. Rather
it pulls in one direction when activated and then stops pulling when
power is removed. You generally need some mechanical mechanism (or just
gravity) to retract the plunger when power is removed. That's why many
solenoids come build into a mechanism with a spring return. One of the
tricky things about using solenoids can be getting the spring
tension/placement just right.
douglas
douglas repetto
There are push/pull soleniods that can both push and pull the shaft
(when power polarity is reversed), but they're rare. They work by using
a magnet as the shaft, rather than a piece of plain steel. That way the
polarity of the electromagnet (set by the polarity of the power supply
hookup) _does_ matter, since there will be an attraction/repulsion
relationship between the poles of the shaft magnet and the poles of the
electromagnet.
But for most purposes that's not necessary and a spring/gravity return
is sufficient.
douglas
Donald Delmar Davis
Thomas Lockney
Actually as an experiment (I was at powells technical) I looked up solenoids in Dan Osullivan's "Physical Computing: Sensing and Controlling the Physical World with Computers" and sure enough there was a great overview from a hardware and software perspective with all of the relevant points made here in it.Everyone on this list should own that book. http://powells.com/biblio/4-9781592003464-2 So just it on your christmas wish list NOW.
Greg Grunest
I found two of those rotary solenoids. I took a picture with my digital
camera to send to you but now can't find the cable. ARGH!
Here is a link to the specs for it.
http://sigma.octopart.com/42163/datasheet/SAIA-H-1079-032.pdf
I found this link in the "discontinued and hard to find" section of the
website.
The bad news is that they appear to move only 45 degrees, not 90 as I said
before, but they might still work for you. And I couldn't tell, but they
are either 12V or 26V. 26V ??!!?? Maybe three 9V batteries in series would
work?
The company that made them is http://www.ledex.com . They have a variety of
really neat solenoids including linear (push, pull, dual-coil push and pull
like the ones that Douglass mentioned and even multi-position quad-coal push
and pull ones) oh and rotary ones too.
Newark carries the newer models of them but they want like... $69.00 -
$94.00 per solenoid!! WTF? However, there is a pretty decent picture of
them at the web site.
http://www.newark.com/jsp/search/browse.jsp?N=0&Ntk=gensearch_001&Ntt=catego
rynumber90051
You can have these two. I'll bring them to the next meeting or call if you
want them earlier. (503) 805-3041. I've actually got a concert on Monday
at the Crystal at 8:00pm so I wasn't planning on being at the meeting but if
you're going to be there I can easily drop them off before 8:00.
- Greg
-----Original Message-----
From: dorkbotpdx-bl...@dorkbot.org
[mailto:dorkbotpdx-bl...@dorkbot.org] On Behalf Of Greg Borenstein
Sent: Tuesday, December 02, 2008 11:49 PM
To: A discussion list for dorkbot-pdx (portland, or)
Subject: Re: [dorkbotpdx-blabber] where to get and learn about solenoids
Greg Borenstein
Those sound really cool. Are you going to be at the Dorkbotpdx 0x02
event on Sunday night, I could get them from you then. Otherwise, I'll
give you a call and figure out a time to get them from you at your
convenience.
Thanks so much for these and all the super clear explaining!
-- Greg
On Dec 3, 2008, at 8:59 PM, Greg Grunest wrote:
> Greg,
>