handicapped pedal actuator

[Carl Meyer]

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I forgot to add the attachments.  When I tried to send them both they didn't
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----- Original Message -----
From: "Carl Meyer" <cmpiano@attbi.com>
To: <pianotech@ptg.org>
Sent: Thursday, December 13, 2001 6:37 PM
Subject: handicapped pedal actuator


> I promised to give some info on pedal solenoids.  Sorry to take so long.
>
> I have quite a few left over pedal solenoids from the pianocorder days.
> There were two sizes.  One was the standard and the other was a heavy duty
> one for the vorsetser.  A picture is attached.  It has an air chamber for
> damping the stroke that never worked too well.
>
> A possible design would be to use two telescoping  tubes spring loaded to
> put under the piano with a fork of some kind to prevent turning at the top
> and a rubber crutch tip against the floor or carpet.  The solenoid could
be
> mounted on that tube with hose clamps and be adjusted up and down to press
> on the pedal.  Lots of fooling around to get it to work.
>
> Now for the schematic of the one I built for a friend.  Realize that this
> was installed in the piano and was not transferable.
>
> First, input is 110 volts 60 hertz.  F1 is a one amp slow blow fuse.   BR1
> is a bridge rectifier, of maybe 600volts at 6 amps.  R1 is 150 ohms at 50
> watts. and controls the hold in current after solenoid activation.  R2 is
27
> ohms 2 watts and charges the capacitor C1  to full 180 volts before
> activation.  C1 is an electrolytic capacitor 220 uf at 200 volts.  The
> capacitor gives a surge sufficient to activate the solenoid and then
filters
> the dc current from R1.  CR1 and R3 are just there across the solenoid to
> prevent arcing and to bleed off the energy stored in the inductance of the
> coil.  R4 is just a bleeder to prevent shock after power is removed.
Values
> will need to be adjusted for each application.  Solenoid may make a
klunking
> noise.  Anyway, that's the basic idea.  Lot's more engineering would need
to
> be done to make it practical.
>
> Feel free to ask me questions, privately if you like.
>
> Carl Meyer  Assoc. PTG
> Santa Clara, California
> cmpiano@attbi.com
>

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