Anything new on foot pedal designs???

[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]

Hi
Here is the place I bought the timing belt and sprocket for my foot pedal.
www.econobelt.com
1--- qpexl37013f08 steel pulley 13 tooth $7.00
1--- qb-xl0208-025 24” belt (or one that is in stock) $4.00
I bought the steel sprocket as the setscrew can be tightened more then aluminum ones.
If you want plans for the foot pedal PM me with your email address.

Have fun
tom

[jtybt]

Went to 2 different Radio Shack. No 50K pots. Not even close. So I'll have to wait before starting.

In the mean time, I've altered the everlast foot pedal to get it a little lower just by cutting away the excess base. Got it in a wedge shape so the heel is pretty close to the ground. That alone makes a big difference in comfort.

[acourtjester]

here is the pot you want http://www.mouser.com/_/?Keyword=785-53c150k&FS=True
have fun
Tom

[parkour]

Ahhh! $9... for a pot?

try digikey.. http://search.digikey.com/scripts/Dk...=potentiometer
select 50k, continuous rotation, click apply filters, then click view page (1).

One of these might work. There are 32 others.
http://search.digikey.com/scripts/Dk...me=987-1322-ND
http://search.digikey.com/scripts/Dk...name=CT2207-ND

[jtybt]

OK thanks guys. I'll check into them. I remembered I have some aluminum diamond plate laying around. I'll check it out to see if it would work as a case.

[ogorir]

Ahhh! $9... for a pot?

try digikey.. http://search.digikey.com/scripts/Dk...=potentiometer
select 50k, continuous rotation, click apply filters, then click view page (1).

One of these might work. There are 32 others.
http://search.digikey.com/scripts/Dk...me=987-1322-ND
http://search.digikey.com/scripts/Dk...name=CT2207-ND

I'm on my phone, so I didn't check the mouser link, but $9 is a fair price for a sealed 2w conductive plastic or mil-spec carbon pot, which is what you want for this type if service.

[parkour]

I had heard of mouser, but did not think they had the deep selection that digikey has.
Then I saw the $9 for the pot and was not impressed.
To be fair, digikey has $9+ 50k pots also.
So I looked at mouser for some other parts I regularly order from digikey, and lo, the price is appreciably less than at digikey

This is awesome
Acourtjester, thank you for linking to that pot.. it made me look at mouser again and found lower prices
I like this

[bigjoeinkg]

When I had my electronics business, Digikey was my last resort for ordering parts. They always were higher on everything.

[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?

[parkour]

Digi-Key FAIL !
Mouser WIN !

Mouser has 153 different 50k linear potentiometers.
http://www.mouser.com/Passive-Compon...=slide&FS=True
I did not exhaustively examine each one, but it looks like any one of those should work just fine. If there is one that is sealed (how?) that would probably last longer if i a foot pedal getting dust and crap in it.

I am liking Mouser more and more
I thought Digi-Key was awesome.. but Mouser is better in that it shows you what you have selected in the parametric search and also allows you to link directly to a search result. Digi-Key does neither.

[jtybt]

I guess I'm a lousy searcher.

First, what would be an acceptable watt rating. .1-.5 watt doesn't sound like much.


For specs, I'd like about 45 mm travel(1.77") for a short pedal throw. but enuff distance for fairly fine adjustments.

The slide POT makes for simple pedal design.


How about that 'start' switch. How do you find that?

[ogorir]

you want a sealed pot of at least 1/2W. a 2w mil-spec would be the best option, as this definitely qualifies as rough service. 2W clarostats are nice: http://www.mouser.com/ProductDetail/...P7PnyDE0bVM%3d

[parkour]

The welder is an electronic device; electronically sensing the pot position. The pot is not controlling power to anything; it functions as an adjustable voltage divider and the welder senses the resultant voltage. Being a 50k pot, the input load must be well over 50k or it would load the pot and it would have poor linearity. This is also a 50k pot. Using ohms law (volts = sqrt(watts*resistance)) we see that it would take sqrt((.1 (watt))*(50000 (ohms)) = 70 volts to dissipate .1 watt in a 50k pot. At half of a watt, it would be 158 volts. It is more likely that the voltage across the pot is between 5 and 24 volts.

This slide has 45mm of travel
http://www.mouser.com/ProductDetail/...9fVD3HTvqDk%3d

Here is a roller switch very similar to what is in the pedal now (at least my pedal)
http://www.mouser.com/ProductDetail/...SNzL3FDxeWs%3d

As ogorir is alluding to; sealing or having a sealed pot is important for a pedal in a dirty shop environment. This slide is not sealed, so you would want to have the pedal sealed up pretty well so that dust and crap doesn't get in and damage the resistor material.

[jtybt]

OK guys, I think I'll get one of each just to try out. Maybe I can find a way to seal that slide rheostat. It would make design Sooooo much simpler. I still have the gear set-up from the Casio pedal to design the rotary POT around.


Oh, and that switch would be perfect. I think I'll get a couple of them.