Who has rigged a motion sound gas pedal?

[David Nevland]

Where did you get the schematic? Did you have to change anything from the scribbled schematic on Motion Sound's website?

[ArasB]

I tried making one myself, but found an easier way (maybe easier). I first used the schematic and parts list from the Motion Sound support site. Ordered all the parts from Mouser, wired it all up, and it didn't work. I replaced the diode and op amp in case I zapped them by accident when I was being careless, but still wasn't working. After double checking my paths and solder connections, I gave up on that design.

 

I then experimented with a 1 Meg linear potentiometer from RadioShack and found that the working range was about 334K ohms for fast and 125 K ohms for slow as measured from one of the legs to the wiper. (One could probably experiment more to find a potentiometer that is even more in the range, but I decided this one would do the trick for now.)

I figured out that to sweep across that working range equals about 1/4 turn of the potentiometer, so I looked for a wah pedal or expression pedal that I had laying around to find one that had the same throw. My Crybaby Wah turns its potentiometer 1 full turn, my Vox turns 1/2 a turn, and my Moog expression pedal turns it about 1/4, so I went with the Moog.

To mount the 1 Meg potentiometer in the Moog, I had to grind away with a Dremel rotary tool the potentiometer shaft to create a Flattened, 'D' shape to slide the plastic piece that is turned by the pedal action. I also ground down the face of the pot to fit more flush. Since the pot didn't fit like the original pot, it isn't locked into place and can spin if forced by hand, so that gave me some flexibility on precision of the flat slot on the shaft. Using a multimeter, I figured out where my working range was, aligned that with the plastic piece and marked it before grinding to get me close.

 

It works well and It feels way more natural when using your feet for leslie control than a footswitch. I'm still not sure why my gas pedal circuit board didn't work, cause it would be nice to have some on-the-fly adjustment of slow limit and fast limit.

 

I hope this helps.

Aras

[wesg]

...............................what feels more natural about controlling a Leslie with a pot than a switch? Do you have variable-speed motors?

 

[ArasB]

...............................what feels more natural about controlling a Leslie with a pot than a switch? Do you have variable-speed motors?

 

All Motion Sound rotating speakers have variable-speed motors.

 

While I can control the variable speed using this pedal to achieve any speed within its range, what makes it more natural than a push-button foot switch is that I know what speed it is without looking down at the speaker. If I am playing on one of my other keyboards (non-organ), and I have to quickly play a line on the organ, I can easily press this pedal to the slow or the fast position to achieve the correct fast or slow speed for the line. With a standard push-button foot switch, however, I would have to look at the LED or look at the speaker to tell if it is going fast or slow before playing my notes.

 

It's a similar effect as the standard half-moon switch on a Hammond - you know the speed of the leslie by the position of the half-moon switch. Imagine if that half-moon switch was a push button switch instead (like most leslie simulator controls) - you wouldn't know what speed it is without looking away from the keyboard and at the speaker or indicator LED.