Hall effect potentiometer

I have logged about 40 hours on a set of BI Technologies 180 degree pots as recommended by thanos in his original post. Cost $15 US each plus $30 US shipping to Aus.

With regards to resolution my wiper arm is set to a maximum range of 180 degrees so the the entire pot is used ie 1 degree of arm movement equals 1 degree of pot movement no gearing required. Now unless I've got it wrong if you use 2/3 of the range of a 3 turn pot you are getting less resolution (no offence to those gearing their pots)

The good thing about these pots is they have no mechanical stops and 0 and 4.8 volts run out at about 10 degrees at both ends of the range so little chance of a runaway servo if tuned first.

Gday @shanothegreat, Yes agree the hall effects are sweet running on the Jrks, the motion is way more defined.
I do not use 180 deg of rotation of the arm because the resulting non linear movement puts my driving way off.
So in turn I only use 90 deg, have tested them at 180 deg too, with the Jrk this is not a bother as the Jrk scaleback values so lets say Im using 100 min and 3000 max in the feedback tab. The Jrk then divided the result of 2900 in to 4096 so there is no resolution loss.

Resolution to me came down to the quality of pot used, on my winches had 5 turn high quality pots - $68 dollars each and that matched the 90 of movement I was using. Almost 100% of pot travel to lever movement, the motion was sharp very responsive.
Now place std ($1.35) pots on my seat mover and notice the motion was slightly sloppy and now and again it just didn't feel right so I thought about gearing but the Jrk should compensate for this with scaleback target, but once viewing the graph I was surprised to see zooming in the value was never stable and little spike were all over the place, mmmm gunna test these hall effect pots.
Well blow me over the motion from the motiondynamic motors running Jrks was absolutely amazing compared to the winch system.

So they get the +1 from me.
If using cheap pots use as much as the rotation as possible, Jrks will compensate for the loss quite nicely and believe the advanced Ard code a lot of guys are now using here does too. Ard's have come along way since xpid.

So I do agree just needed to clarify what I found by testing them for years on many motors and different feedback systems. Wish they had encoder capabilities for position.

Also done a runaway test with the hall pots and too my surprise the motor actually didn't error, kicked too far and return back the max I had set. Normally on std pot it threw a feedback out of range error, so in my opinion anyone starting their first build, buy cheap pots and break a couple without worrying about the little cost once you have it nice then mod the sim with some hall effects.

I’m glad you and bsft decided to give the hall effect pots a go again! A lot of people rely on you’re advice so now you are better equipped to advise them what the best pots to use are based on their particular setups! Thanks to you both!

Btw My 3dof rig uses hall effect digital encoders but they output a pwm signal, not a voltage. They will register the full range of the pot (360 degree) and output a number from 0 to 4095. There are two issues with using these though. One is they are very expensive at $85 each (with connector and wire). Second they can be slow to read. They output a single pulse pwm signal so the length of the pulse determines the reading. So at 1 degree the signal pulse is only 1us. But at 359 degrees it is 4095us which is ridiculously slow (1us per degree). But the only job my picaxe needs to do is read them and send the information to my PC so it does the job adequately enough!

http://www.usdigital.com/products/encoders/absolute/rotary/shaft/ma3

They do have them available with analog output but only at 10bit and still very expensive.

G'day eaorobbie, sorry I should have also qualified that I predominantly have my sim tuned to use just over 90 deg of the range of the output arm, ie that is 45 deg up and 45 deg down.

I'm using a 60 mm long arm on the wiper motor set at 90 deg to the long arm connected just behind the shoulders, pretty standard stuff.

The input to the hall effect pot is connected directly to the motor output shaft so as to avoid and slop or backlash associated with gearing. I too chopped out some cheap one turn pots with poor PID and direction settings, cost of development I suppose.

Like yourself I found the cheap pots had a very short life span and quickly sought out the hall effect ones. In my set up I have found that I can set the mid point in the Jrk utility app to 2048, loosen the lock nut on the pot and turn it to set the optimal angle of the wiper output arm to the control rod then tighten the lock nut.

Being non contact the are very stable and electrically noise free, the reason they are preferred in modern day drive by wire car throttle bodies I suspect.

@BlazinH , its the first time I used hall effect pots actually, and finally after finding somewhere that was cheap, I use them from now on.
Although the desk racer is running cheap pots at the moment, just waiting for more hall effects to turn up.

I have my pots in from Farnell.. actually the first item that have arrived
I will try and print some gears on my 3D printer, so that I can use the full capacity of the pot .. instead of the few degrees we would have otherwise..

Lucky you, im on 3+ weeks of waiting on my Pots, Just called today and STILL stuck in customs.

Bastards. mine turned up yesterday over a week late. I was slightly annoyed as I had to go spend another $72 on a pair of 360 turn pots a week ago to get my setup running properly.

I called element this morning and asked WT* is going on with my order. STILL in customs are you freeking kidding me. they were in customs early last week.

So after talking to a nice lady Shauna she opted to send me out a new set of pots with Priority shipping which I WILL receive within 4-5 business days. 50$ fee Waived thank you very much.

I kept my original set of pots coming for buddy who's contracted me to build him a rig exactly like mine.

overall happy with the Customer service but Horribly disappointed in the shipping from them.

I personally dont believe ANYTHING should take 3+ weeks to ship from the UK to the US. UNLESS its on the Slow boat across the water, which it isn't.

customs hold up..........."description of product - pots, must be drugs, lets hold it for weeks on end even though x-ray doesnt show any narcotics". I wonder if customs dont have anything better do to sometimes..

makes me wonder as well buddy.

If you need more in the future you can get them in North America from Digikey:

Canadian site:
http://www.digikey.ca/product-detail/en/6127V1A180L.5/987-1387-ND/2620657
US site:
http://www.digikey.com/product-detail/en/6127V1A180L.5/987-1387-ND/2620657
In stock and quick to ship, mine showed up the day after ordering.

Thanks for the Tip Roonster, I've actually got a spare pair that i received from Element after my first pair went all gritty, Technically They are still working so Im going to wait for a complete FAILURE before i replace them with the new ones.

Even a few $$ cheaper on Digikey, Awesome. Ill for sure use them in the future.

I found these at a good price ... 12,00 € single piece the only thing that I do not square and the letter ends with 6127V1A180L.5FS code (FS) final. are the same?

http://www.digikey.it/product-detail/it/6127V1A180L.5FS/987-1392-ND/2620661

They are the same internally. The FS stands for flat shaft or slot I believe.

they are not cheap! because of duty taxes... google something like "digikey duty" in your own language

I bought mine at farnell: no taxes

your profile indicates "fast e furious" but to prevent an error, you can take the time to read the specs: each letters and numbers are explained!
yours

Lol we don't get hit with duty taxes from Digikey , lol.

Really after nearly 90 hours on std 2 buck pots they still going strong, mounted exactly the same way my hall effects bound themselves up in 60hrs of use (about 2 weeks of driving for me), I prefer Wire Wound got one rig now close to 5 years old still going strong with the same pots.

Just be careful on the mounting, any off centre movement will cause the hall to fail quickly. Been there done that, threw'em out.

@BlazinH , I recall you use rather expensive hall effects? about $140 each or something?

@ BlazinH Thank you and all clear now


@ Racingmatto Ok if you do not pay taxes worth I order from Farnell.

Things a joke? Instead of making jokes because I did not explain what they mean letters and numbers you master? Professor or should I call? I asked him here on purpose because I do not know electronics ... so?

@bsft My first rig uses hall effect encoders at 12bits with 360 degrees rotation and output a pwm signal equivalent to their position. They cost about $80usd each. I used encoders instead of pots because most microcontrollers (including the one I’m using) have a 10bit analog to digital converter for reading the pots and I wanted to use the full 12bits.

However, my new rig uses the cheap hall pots. I only need to read 90 degrees rotation for it instead of 360 so reading 90 degrees at 10bits has the exact same resolution as reading 12bits at 360 degrees. So the actual resolution of both of my rigs feedback is the same. I don’t have an exact hour count on my hall pots but it has to be well over 100 now on three of them and still no issues with any yet! Since the shaft and bushing are the only pieces that wear, as long as they always turn quite freely in their mounts, they should last for some time. I see no reason why they shouldn’t last as long as a standard pot that uses a bushing for a bearing too.