hand pedal+ foot pedal

[plen]

i posted this on another forum and got no reply so i will try here.  i have a diy shin ei univibe. can i can i add a hand speed pot inside the univibe and still have the foot pedal. would both work.

thanks.

[antonis]

Do you mean idependently working pots..??

[plen]

yes two different pots. i have wired three wires from the din socket to a duel reverse log pot inside the univibe. that works but it stops working if i plug the foot pedal plug into the din socket. i have nearly made a foot pedal. i have just to workout where the two wires go to on the stop switch at the heel of the pedal.

[idy]

How to have both work, to be able to reach down with the hand and select a speed, and then sweep faster or slower with the pedal?... Not sure it there is a good simple way to get that... to have the full range of speed "choosable" from two pots (each one of which would itself be a double gang.) Neither series nor parallel will work...no?

Maybe have a foot pedal with a bypass switch, like a wah. When you go toe forward (yours switches at the heel?) and press you hit a switch and choose between the two methods... but how many poles would you need... 3 poles. You can do that.

But you will need more wires (six? five?) coming into your foot pedal. Or maybe only four... There is some normally closed switch in the DIN plug that you want to move that function to the footswitch...

[plen]

idy i dont mean the two working at the same time. i mean use the hand pot when the foot pedal is not plugged in and use the foot pedal when the hand pot is turned down to 0.

[idy]

Makes sense. The thing is to figure out what connnection is being broken when you plug the pedal in. That connection will have to be made by the new switch...

What about having both the foot treadle control and the "manual" speed pot in the same enclosure? Then it really is just switching the three wires between two double pots.
I'm not sure about the "when the hand pot is turned down to 0." Do you want a switch built into the pot? Don't know about double pot + 3p switch....
I really think you are better off using the treadle to select manual/foot. And having both pots in the treadle enclosure. Other wise I think you will need more than 3 conductors.
And this is kind of a vintage effect. Do you really need to drill holes in it and etc?

[idy]

Have you found the schematic that includes the pedal? Looks like five conductors, R W K Y BL. W and R do the "cancel" function which instead of bypassing turns the lamp off. K Y B do the pot, sounds like you know that.

[Mark Hammer]

It's obviously possible, since actual Univibe pedals would have this feature.  However, as you know, the LFO on a UNivibe uses a dual-ganged pot. and those can be a little trickier to work with.  That's also why the jack/plug has multiple pins and is not a simple T-S or TRS type.  Not only is there more wiring involved, but not all foot-pedal shells accommodate dual-ganged pots easily.  The pots certainly won't get the same workout that wah pots do, but you still won't have an easy time finding dual-ganged pots that hold up over the long run.

All of that said, because of how the internal dual-ganged speed pot is wired, one possibility is to use photocells in parallel with the speed pot, and control the brightness of an LED or other lightsource, with the footpedal.  That would only require a regular single pot, and could very probably be done with an off the shelf volume pedal and a TRS jack.

The photocells would need to be reasonably high dark resistance, so that their parallel resistance wouldn't "corrupt" the onboard speed setting.  So, ideally,  something like 1meg+ dark resistance.  If you're using the footpedal, simply set the onboard speed control to slowest rate, and the footpedal would reduce their combined parallel resistance to achieve faster speeds.

Like all optical systems, if you're not using commercial single or dual vactrols, you need to match the sensitivity of the photocell with the spectral content of the lightsource used.  You'd also need to assure that the footpedal circuitry provides a suitable amount of current feeding the lightsource; not too much and not too little.

[plen]

just finished building a foot pedal for my clone shin ei univibe. everything works as i wanted. i can use the duel reverse pot in the univibe or i can use the foot pedal. thanks everyone for your help.