Anything new on foot pedal designs???

[jtybt]

In the mean time, I got a Casio foot pedal for a musical inst like elec piano or guitar or something or other. One of the guys put up a mod someone else did to adapt it to the harbor freight 130 TIG... the post by Parkour and his link.

http://www.mg42.us/viewtopic.php?f=10&t=7208&start=0

Internally it has a toothed lever that engages a gear that steps up to a larger gear that turns the POT. The pedal movement is short and turns, thru gearing, the POT 7/8 rotation. The Everlast POT turns 3/4 rotation so there's plenty of room to adjust for full movement. All I have to do is make a bracket to mount the toothed lever/foot pedal to pivot on and a bracket to hold the POT and one to hold the gear shaft. The only thing is the gears turn the Casio POT counter clockwise so I'll have to flip the Pot.






The neat thing, the gears are the same pattern as a sewing machine belt so I can do a mod like acourtjester did if need be.

[parkour]

Don't flip the pot, you just have to reverse the two outer wires on the pot; leave the center wire at the center. Reversing the outer wires will reverse the logic of how it operates. Furthermore, if the full travel of the pedal does not move the pot through its full travel, you will have a slightly limited amp window.. you will not be able to hit both min and max amps on the pedal with the available stroke.

In linear 50k pots, digikey http://search.digikey.com/scripts/Dk...=potentiometer
has 250 260 280 295 300 312 314 degree rotation pots. Some will be easier to mount than others.

You can get an idea of the actual rotation. Count the number of teeth on the gear that is on the pot. Count how many of the pot gear teeth are contacted by the gear that turns the gear on the pot.
Pot_Rotation = 360 * (Contacted_Teeth / Total_Teeth)
Suppose the gear has 24 teeth, and 20 of them are contacted.
You would say 360*(20/24) = 300 degrees.
You would want a 300 degree pot.

Another option is to count the pot gear teeth and the teeth on the gear that turns the pot gear. Mark one of the teeth on the gear that turns the pot gear, press the pedal, and count the number of teeth that pass from where you marked. This way you can determine exactly how many degrees of pot rotation you want. This is a very simple and exact approach.

If you mark a tooth and take a pic of it then move it to the other extreme, and take another pic, I can easily determine the exact number of degrees that it rotated.

[jtybt]

Hey, That's REAL good info! Gotta remember that.


It's the geared pedal that has 315* of rotation and the everlast has 270* so There's extra rotation. I just have to set the teeth at max rotation and let it back off to get to zero.


I've been fiddling with the everlast foot pedal and repositioned the pivot for the pedal a 1/2" lower and cut away the heel to give it more travel cuz repositioning the pivot reduced the travel. Didn't hurt much welding on small stuff cuz I wasn't using that much amperage. In fact I had smooth starts. Had to bend the 'start' switch to start at the beginning of pedal travel, maybe that helped

[acourtjester]

I find it was easier to look around in Mouser then digikey but that may be cause I'm an old f**T
Spent to many years chasing bytes, Navy time then the space center then main frame computers then medical electronics (CT & MRI). Retired now spend my time making projects, Fun City.

[ogorir]

I agree, digikey's website sucks. mouser's search almost always gets me what I'm looking for, unless it's one of those oddball HV parts for tube amps that they just don't stock.

[jtybt]

My problem is I don't even know what to look for. I know it's a 50K pot but that's about it. I couldn't tell if it was a good one or not.

I was also interested in a sliding POT, kinda like them sliding volume controls. That would make it really easy to make a pedal almost any size and shape you wanted.

[parkour]

Digi-Key has the most usable self service website I have ever seen. The parametric search is hard to use if you don't know what you need, but if you do, it will send you to the exact part you need. Well, it looks like mouser has a parametric search also. I am liking them more and more

Anyway jtybt, you know you need a pot that is 50k. The next parameter you care about is how many degrees it rotates, this gets back to my earlier comment about determining the degrees of rotation by counting gear teeth and such.

Once you determine how many degrees you need, then you can use the parametric search to sort for pots with that number or fewer degrees of rotation. After selecting 50k and the number of degrees you need, then just browse through the results and find a pot that looks like it will mount up easily.

Mouser only allows me to select "1 turn" pots. Digi-Key has several different pots listed that would qualify as single turn, but have different numbers of degrees of rotation.

[jtybt]

Ok I'll give it a try. The geared pedal gives the POT 7/8 of a full revolution so about 315* of rotation.

By the way, how would you look up a sliding POT?

[acourtjester]

Here is the switch I used on my foot pedal http://parts.digikey.com/1/parts/976...m-e14-00h.html
I bought mine from Surplus Center but they don't show them now. Mouser don't stock them either.