From list@sevush.com Thu Dec 25 17:00:28 2003
Subject:RE: Speed Control Pedal

Ron, thanks for turning my cryptic (but well founded) concern into bite
size chunks all could understand.

There's another problem in this potential setup - Leslie motors are
brushless and brushless motors really don't like to have their voltages
varied. I have heard from many Leslie experts and fanatics that the right
way to do this is varying - and this is where I'm fuzzy, either the
frequency or the phasing of the AC - but NOT the voltage. The end result of
using dimmers, rheostats, etc. is the motor burns out.

Perhaps it takes a long time before that occurs, and maybe the cost of
replacing single speed Leslie motors is worth it. I myself plan to either
purchase the Hampton kit for $250 or try wiring my own version, using a 555
timer on a nice solid state relay I've inherited from Ben Kuris Labs.

> I viewed Dan S' response as a safety issue rather than a
> musical one. A pedal unit designed for volume control most
> likely would have the low side of the pot (ground) tied to
> the units case for shielding. Also, a pot designed to handle
> line voltage usually has a plastic shaft and is mounted to
> insulate the pot from any casing that could be touched.
>
> The sewing machine pedals that you mentioned typically are
> wire wound rheostats, stepped with a multi position switch
> and wire wound resistors, stepped with multi position
> switches (or commutator) and coils or with a simple
> autotransformer. They are designed for the high power of the
> motor. Also, when controlling with a variable resistance it
> is necessary to approximately match the resistor to the
> motor. Anyone that has ever done stage lighting with an old
> rheostat (pre variac) board would probably remember that if
> you put a small bulb, like a table lamp, on a dimmer rated
> for say 3000 watts, there would be virtually no dimming.
>
> Pedals that designed for volume control typically are
> designed with carbon (or newer technologies) potentiometers.
> They typically can handle 1/10 watt to 1/4 watt. A motor
> directly controlled with one of these pots would turn to
> useless carbon in less than a second.
>
> I suspect that the control method that Sam was using was a
> control voltage to a power controller in the box that was
> mounted in the Leslie. Jameco Electronics
> http://www.jameco.com/ sells a Velleman DC Controlled Dimmer
> Kit http://www.vellemanusa.com/ M/N K8003, for $22.95. The
> Jameco P/N is 128901CD. This unit uses 0 to 10 volts DC
> which a volume pedal should be able to handle safely and
> would probably be able to control the motor. (Assuming the
> motor current is within the 3.5 amp limit for the
> controller.) From the toroid choke, that I see in the
> picture, it appears that they payed attention to filtering
> the switching buzz.
>
> One final note. It is never a good recommendation to use
> audio connectors (that are used for audio elsewhere in a
> setup) for line voltage. Phone jacks/plugs are especially
> bad because they aren't really physically robust and break
> easily. I have used XLR3 connectors for power when I'm not
> near other uses for them. They are physically more robust
> (read physically safer) and since the XLR series also comes
> in 4,5 and 6 pin models it is possible to use one of them for
> power near an XLR3 audio system. That said, it is still best
> to use connectors that are designed for line power when
> connecting line power. If an accidental connection is made,
> the money saved by using existing audio cabling and
> connectors could be eaten up with the cost of replacing one
> or more pieces of equipment.
>
> Ron
>
> ----- Original Message ----- From: jake92028
>
> --- In CloneWheel@yahoogroups.com, Dan S wrote:
> > > does a stock pot in a volume pedal handle 120 volts ac
> out of the
> box?
> >
> > Wouldn't want to put my foot anywhere near it.
>
> Musically, it's a matter of taste = like it - hate it. Per safety,
> it'd be as safe as putting your foot near a household
> extension cord
> or the power cord on an amp when the job was finished and any bare
> wire soldered connections were taped up or covered with heat-shrink
> or even cold-shrink shielding. It's also easy to make these with
> phone jack/plug connections connected to the wires once you
> "get" how
> this works. Wj
>
> ----- Original Message ----- From: jake92028
>
> --- In CloneWheel@yahoogroups.com, goff747@a... wrote:
> >
> > In a message dated 12/25/03 9:39:04 PM, jake92028@y... writes:
> >
> > << Hand me any working pedal with a
> >
> > potentiometer that'll manage 120 Volts AC >>
> >
> > does a stock pot in a volume pedal handle 120 volts ac out of the
> box?
>
> I'm not sure, but I think so; easiest is to unscrew and remove the
> bottom plate so the potentiometer is easy to see, "Oh yeah,
> so that's
> it." Then take it into an electronics parts shop and have a real
> (non-Ratshack) tech tell you what voltage the "pot" could handle.
> I've heard of sewing machine pedals being used; they run their
> machine's motor faster and slower. Wj
>
> ----- Original Message ----- From: jake92028
>
> --- In CloneWheel@yahoogroups.com, ZAKEMO@A... wrote:
> > In a message dated 12/25/2003 5:39:25 AM Pacific Standard Time,
> > jake92028@y... writes:
> > > Always
> > > go to the source, i.e., the AC power cable to the Leslie motors.
> >
> > What I remember is the Farfisa pedal workings had nothing to do
> with the
> > electronics. Sam had rigged a little pod of some sort on the side
> of it. Wire/cord
> > from pedal then went directly to a little box he made
> that sat near
> the upper
> > Leslie motor. Leslie motor then plugged into said box. Power was
> received
> > from where the motor used to be plugged into the chassis.
> No power
> or inner
> > workings were used from the Farfisa pedal, it was just
> used for the
> foot action to
> > the little pod. Only controlled the upper rotor. I never spun the
> bottom one
>
> Yes, one of these pedals has nothing to do with electronics, only
> electric power. Varying just the top motor's electric feed/speed
> would be a nice horn effect, just as you describe. Sounds like Sam
> was using the gear turning mechanism inside the Farfisa
> pedal to turn
> a pot (potentiometer) attached to its side. Electricity would flow
> from the box the Leslie motor was plugged into through the pedal's
> cable. Once you take the bottom off a pedal and see how simple the
> turning mechanism is that turns the little round pot's driveshaft,
> this idea is clearer to understand. Wj
>
> [Non-text portions of this message have been removed]
>
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