[dorkbotpdx-blabber] where to get and learn about solenoids

[Greg Grunest]

Greg,

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-blabber-bounces at dorkbot.org
[mailto:dorkbotpdx-blabber-bounces at 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,

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

On Dec 2, 2008, at 11:38 PM, Greg Grunest wrote:

> Greg,
>
> 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
> greg at grunest.com
>
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