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

[Greg Borenstein]

That's awesome, Greg!

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,
>
> 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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