High-force Push Solenoid
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High-force Push Solenoid mtowns 07-04-2006
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Posted by mtowns on July 4, 2006, 7:52 pm
Hi, I am having some trouble looking for a push solenoid that I need
for a project.

I am looking for a push solenoid capable of pushing at about 5 kg.
Furthermore, I want to be able to vary this force. I am using this to
push a fully weighted piano key to create different loudnesses, so the
dimensions of the solenoid need to be relatively small. Does anyone
know an appropriate device for this application, or shall I be forced
to make my own?

Thanks for your help.


Posted by MetalHead on July 4, 2006, 8:19 pm
mtowns wrote:
> Hi, I am having some trouble looking for a push solenoid that I need
> for a project.
>
> I am looking for a push solenoid capable of pushing at about 5 kg.
> Furthermore, I want to be able to vary this force. I am using this to
> push a fully weighted piano key to create different loudnesses, so the
> dimensions of the solenoid need to be relatively small. Does anyone
> know an appropriate device for this application, or shall I be forced
> to make my own?

Hi,
Try a place that supplies pinball repair parts. They probably won't be
marked for the force availible, but there are many varieties to mess
with. It has been a long time since I searched through solenoid vendors
catalogs, but as I recall, 5 KG is a lot of force from a solenoid.

Another thing to think about is that powerful solenoids will heat up
quickly if you hold them energized. Some of the pinball solenoids have a
separate holding coil that will not provide as much force, but it will
not heat up as fast while keeping the plunger pulled in. When the
solenoid heats up, it's DC resistance increases, so it will have less
force on subsequent operations until it cools.

The force is proportional to the current in the coil. You can control
the force (and correct for thermal issues mentioned earlier) with a
current source drive instead of a voltage source drive circuit.


Good Luck,
Bob

Posted by Brendan Gillatt on July 5, 2006, 12:16 pm
mtowns wrote:
> Hi, I am having some trouble looking for a push solenoid that I need
> for a project.
>
> I am looking for a push solenoid capable of pushing at about 5 kg.
> Furthermore, I want to be able to vary this force. I am using this to
> push a fully weighted piano key to create different loudnesses, so the
> dimensions of the solenoid need to be relatively small. Does anyone
> know an appropriate device for this application, or shall I be forced
> to make my own?
>
> Thanks for your help.
>

5Kg is a hell of a lot of power from a solenoid - you will be drawing
several amps at 24v for that sortof thing. I suggest making your own
using an electric door lock magnet (energize to lock) with a plate of
iron/steel and a through-hole shaft.

Side view:
Sheet Iron
/
=======||=======
_____ || _____
|_____||||_____|-Magnet
||
||- through-hole shaft.

When the magnet energizes it pulls the plate of iron down and pushes out
the shaft.

You may need to drill the hole yourself for the shaft and a return
spring would probably need to be slid between the magnet and the shaft.
Some of these magnets run off 24v and so could be PWM though a lot run
from mains.

Posted by Wayne Lundberg on July 5, 2006, 4:14 pm

> mtowns wrote:
> > Hi, I am having some trouble looking for a push solenoid that I need
> > for a project.
> > I am looking for a push solenoid capable of pushing at about 5 kg.
> > Furthermore, I want to be able to vary this force. I am using this to
> > push a fully weighted piano key to create different loudnesses, so the
> > dimensions of the solenoid need to be relatively small. Does anyone
> > know an appropriate device for this application, or shall I be forced
> > to make my own?
> > Thanks for your help.
I discovered that solenoids used in things like washing machines and the
like behave very well with a variable speed resistor much like what you use
in dimming lights in the living room after sipping that glass of wine with
your most significant other and.....

But these are pull mechanisms, so you need to create a fulcrum and lever
device and have them work upside-down on your piano. So a linkage is
required. But the force control with the light-switch control is quite keen.

I have a breadboard of the device I'll be happy to photograph and send to
you you'd like to see it.

Wayne



Posted by Fulliautomatix on July 7, 2006, 4:36 am
mtowns wrote:
> Hi, I am having some trouble looking for a push solenoid that I need
> for a project.
>
> I am looking for a push solenoid capable of pushing at about 5 kg.
> Furthermore, I want to be able to vary this force. I am using this to
> push a fully weighted piano key to create different loudnesses, so the
> dimensions of the solenoid need to be relatively small. Does anyone
> know an appropriate device for this application, or shall I be forced
> to make my own?
>
> Thanks for your help.
>

I have made solenoids in the past from automotive starter solenoid coils.

These flow 20A @ 12V and push ~ 20kg.

Haven't seen a commercial one more than 2kg or so from
mmemuri?...momery?...ummm...memmeri...yer, thassit!

Stroke may be a problem too...you will need 10 odd mm to operate a piano
key no?

If you make your own solenoids (88 of them?) they can be placed closer
together by using long & short actuation rods... _-_-_-_-

And use steel cases to provide a magnetic circuit...the end cap is
important in hold applications, but if you are going for a linear force
adjustment via current control it may not be needed




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