Variable Resistance (potentiometer-like) Foot Pedal? - Page 1
Forum section: electronics / projects

author: PhysicsDude55
author_rank: Contributor
timestamp: December 19, 2019, 12:07:52 am
content: Looking to do some projects that involve controlling something (via microcontroller) via a foot pedal, and want variable speed. Ideally looking for a self contained foot pedal that has an internal 0-10Kohm potentiometer, or something similar that could be wired to generate a 0-5v or 0-12v signal.I know modern gas pedals in cars do this, but they're not self contained or easily mountable where you could put one under your work bench. Maybe I'm wrong about that.Anyone have any experience with this? Was thinking maybe foot pedals to control TIG welders? Sewing machine foot pedals? Anyone have any experience with the internals of those?

author: andy3055
author_rank: Super Contributor
timestamp: December 19, 2019, 12:59:54 am
content: If you are prepared to pay the price, check these out:https://www.amazon.com/Linemaster-OHASAB-10K-Electrical-Momentary-Compatible/dp/B005GRE12Uhttps://linemaster.com/product/429/Varior-Potentiometer/09ASXP-10K/

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 19, 2019, 01:16:31 am
content: Newer sewing machine pedals are just potentiometers (as opposed to a complete speed controller in the older ones) but I'm not sure what values are commonly used.

author: Mr.B
author_rank: Unknown
timestamp: December 19, 2019, 01:23:34 am
content: I made one for my lab myself.Extreme backyard edition:20K linear slide pot removed from an old audio mixing deskOne springOne lightweight hingeA couple of pieces of plywoodHand full of nuts and boltsIt isn’t pretty, but it worksEdit: If you had a 3D printer you could do a pretty good job.I have a 3D printer, but have not yet replaced my original contraption, because it just works.

author: DaJMasta
author_rank: Super Contributor
timestamp: December 19, 2019, 01:31:38 am
content: A regular pot with a cam on the shaft that was joined to the bottom of the pedal would be able to do it, just a matter of making everything durable enough to be used underfoot and stay repeatable.If you want more exotic options, maybe a block of foam and an force sensitive resistor under the raised part of the pedal? Maybe a tube with an IR proximity sensor looking up at the bottom of the pedal? They're cheap enough that an integrated IMU could probably just give you digital angular data and then you just need a physical pedal that feels good enough.

author: edavid
author_rank: Super Contributor
timestamp: December 19, 2019, 01:34:53 am
content: Guitar volume pedals are readily available from music stores or eBay. You might want to swap out the pot for linear taper.

author: Someone
author_rank: Super Contributor
timestamp: December 19, 2019, 03:15:59 am
content: Quote from: edavid on December 19, 2019, 01:34:53 amThere is also a "expression" pedal that is a linear taper.

author: techman-001
author_rank: Frequent Contributor
timestamp: December 19, 2019, 03:27:33 am
content: Quote from: PhysicsDude55 on December 19, 2019, 12:07:52 amThe old sewing machine foot pedals used a "carbon block" made of small carbon "coins" as a variable resistor. Depressing the pedal compressed them, reducing the resistance and increasing the power to the small DC motor powering the machine.I replaced one once with a magnet in the pedal and linear Hall Effect sensor in the body. A spring held the pedal (and magnet) up and away from the sensor in the body. It was repeatable and reliable, so I recommend this method.It can be easily made with a hinge, spring and wooden parts. Varnish them and it will also be neat and good looking.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 19, 2019, 05:03:21 am
content: I have also found older sewing machine pedals that have nichrome coils with a slider driven by the pedal. But the way it was mechanically arranged it only provided about eight unique resistances. Evidently that was good enough for the market.I would recommend rolling your own as others have said. Think about your application. If the operator is sitting, hinging at one end is suitable. If the operator is standing you may want a pivot near the middle so that weight can be supported and just shifted from heel to toe. In either case you will probably only get couple dozen degrees of pedal rotation. You will need some kind of mechanical gain to match the roughly 270 degrees rotation of most pots. That might take the form of a belt and pulley system or a rack and pinion setup (a number of toys have suitable pieces) if you want a linear relation. There are some other options but are probably too hard to fabricate. And you can always accept using just part of the pots rotation and fixing the problem with a high resolution digitizer and software.

author: AG6QR
author_rank: Frequent Contributor
timestamp: December 19, 2019, 07:04:51 am
content: Music stores sell volume pedals for guitars, which are potentiometers with a tiny bit of wiring and two 1/4 inch phone plugs.

author: Electro Detective
author_rank: Super Contributor
timestamp: December 19, 2019, 08:48:04 am
content: Any musician guitar, bass, keyboard 'volume pedal' that has a standard pot in it can be modded with a pot in the value and taper required.Tip: try the pot you think you need first before fitting,and buy some exact value spares once you've got a winnerIf you can't find a volume pedal, gutting out a stuffed wah or swell pedal will do the same job,as long as it's mechanically oki.e. the pedal and gear parts workSome pedals have opto-couplers? instead of pots, watch out for that

author: rvalente
author_rank: Frequent Contributor
timestamp: December 19, 2019, 09:36:07 am
content: Tig welders uses pots for controlling tje current, check for them, im sure they are plenty available on ebay and similar

author: MagicSmoker
author_rank: Super Contributor
timestamp: December 19, 2019, 12:26:28 pm
content: Quote from: Electro Detective on December 19, 2019, 08:48:04 amMaybe not so standard, in my experience. I made my own TIG foot pedal a couple years ago because I refused to pay $700 to Miller for essentially the same thing that would cost a musician $30. What I found after taking apart several pedals was that the pots inside are often strange multi-track beasts with no stops (ie - free spinning), unpredictable resistance spans (not a one went all the way down to 0R), and which are usually mounted by being captured in a split compartment in the enclosure body (ie - not bolted to something, presumably to allow for slop in the various mechanisms). In short, these things tend to be value-engineered to the penny and therefore not quite as amenable to hacking as might appear.

author: rvalente
author_rank: Frequent Contributor
timestamp: December 19, 2019, 02:08:22 pm
content: Another option would be gas pedals from cars, there are plenty of options and I'm sure chinese or you local dealer can support you.They're are basically two pots inside, some in opposite directions. Supply them with 5V and bang, there is your output.Simple, ergonomic, very robust and maybe cost-effective.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 19, 2019, 03:01:08 pm
content: Quote from: rvalente on December 19, 2019, 02:08:22 pmYep, you can find many of those used on eBay and others for cheap. They are usually easy to use as there's not much more than two pots inside as you just said (they are rarely active).The fact they have two pots for redundancy is also a plus.

author: rvalente
author_rank: Frequent Contributor
timestamp: December 19, 2019, 03:04:40 pm
content: Quote from: SiliconWizard on December 19, 2019, 03:01:08 pmThere is a series from Hella Automotive that employ a very fancy capacitive technology, instead of a pot with a wiper there is a mesh over a pattern, but the output still is a analog voltage. I have not yet seen can bus gas pedals, but that's off topicI'm not in US but, here in brazil I can find a used gas pedal, nom model specific around 10 bucks

author: Electro Detective
author_rank: Super Contributor
timestamp: December 21, 2019, 08:56:37 am
content: fwiw there is no shortage of muso pedals in this part of the world, loads in pawn establishments tooall the ones I've sorted had 10k or 20k? standard pots IIRC and some sort of stop travel thingie in the gear arrangementand yes, a cheap TIG pedal will do the job, that's IF you can find any cheap ones.Weldors with no clue about electronics are easy targets for motormouth sales goons flogging overpriced 'former reputable brand name' crap in thick powder coated metal housings,in familiar blue or red, and lately in yellow and green too.

author: PhysicsDude55
author_rank: Contributor
timestamp: December 25, 2019, 05:26:55 am
content: Thanks everyone for your replies and suggestions.It looks like there are a bunch of ~$25 foot pedals for newer sewing machines that are just an internal 10K POT with a 2 wire connection.According to a review on this Amazon listing:https://www.amazon.com/Foot-Control-Pedal-XC6651121-Brother/dp/B0038RENYQ/ref=pd_sbs_328_7?_encoding=UTF8&pd_rd_i=B0038RENYQ&pd_rd_r=c6f0784a-04dd-4e03-8e7e-b4c3df3a2bc1&pd_rd_w=bKeL7&pd_rd_wg=qGFSH&pf_rd_p=5873ae95-9063-4a23-9b7e-eafa738c2269&pf_rd_r=J52VYNY8H2ACQK9HQKX1&psc=1&refRID=J52VYNY8H2ACQK9HQKX1There is a linear 10K pot inside with a microswitch to make an open circuit when the pedal isn't pressed. Looks like this same model of pedal (probably from the same chinese manufacturer) is all over ebay as well. Just make sure it has the 2 conductor 1/8" (?) mono style plug rather than any sort of mains connection.