handicapped pedal actuator

[Carl Meyer]

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