I've been pretty lax in getting this particular project done. I wanted to replace the ultra-noisy cheap pots I used in the '109 with hall effect devices. The video below shows the prototype of the replacement.

I'll post detailed build pics later. The design is based on the work of folks like Sokol1(sp?). The whole thing can be built for about $5 each.



(and yes, the volt meter is very, very old. )

g.

Cool! Can't wait for the build pics!

Here's the parts you need:



The parts shown are a 22MM bearing (just a little shy of 7/8" diameter), two 1/4 x 1/4 neodymium magnets, an Allegro A1302 hall effect sensor and a Bic pen body.

Using a vice, carefully press in a short segment of pen body into the bearing - do NOT hammer it! The pen body plastic is very brittle. Steady force using a vice will "drift" in the pen body quite easily.

Next, glue the two neodymium magnets to opposite sides of the pen body - the magnets should be oriented N-S (they'd come together if the pen wasn't in the way). The way I did mine was to rest the magnet on the inner race of the bearing with a business card keeping it from physically touching the race. I then used "thick" CA (cyanoacrylate) to glue the magnets in place - have some kicker handy to speed up the cure process.

You should end up with something that looks like this:



Now you need to build the board that will hold the sensor in place. I used a small slice of copper clad perf-board. This holds the 3 pin connector and the A1302 very well.



Next, you want to get some 1/2" or 3/8" plywood and bore a 7/8" diameter hole in it using a forstner bit. Dont' bore the hole completely through - leave about 1/8" of material. Then drill a 1/4" hole using the same center as the 7/8" hole. I use a set-screw to hold the bearing in, but you could easily hot-glue it in if you're careful to keep the glue out of the bearing races. Tape the bearing in for now so you can align the hall sensor properly. A properly aligned sensor will fit in the center of the pen body with the magnets on either side of it.

You should end up having something that looks like this:



Assembled, it should look like this:





You can connect any kind of pushrod arm, gear, or whatever to the pen body - just don't apply too much side force to it. Too much side stress will crack the plastic. This setup gives 180 degrees of usable travel and works very well! The bearing size that you get should have an inner diameter just a tiny bit less than the widest point on the hexagonal Bic pen body. This allows for a very tight friction fit that doesn't require any adhesive to hold it in place.

You can easily custom design your own bracket for this - this was a simple prototype that proved out the technique and a refined version will end up in my '109 as well as a replacement for the pitch axis sensor I screwed up in my BRFS gimbal build.

Enjoy!

g.

That's really impressive DIY skills! Good job and thanks for posting it!

So, can a hallsensor setup like that one be used as a replacement for a regular joystick pot?

What's the smallest possible diameter of the hole that fits the hallsensor?

Thanks Troll. The A1302 is .164" wide, so anything with an inside diameter of say .170" or larger would be fine.

I built this thing to replace some really cheap and noisy pots that I used in the '109 build. It will replace any three wire pot.

g.

Instead of a Bic pen, could a solid piece of plastic rod be used or even a metal rod (say aluminum so it's not magnetic)?

I can't seem to find that brand of sensors. What spec is that sensor? I have a local supplyer of honeywell hallsensors. Maybe I can find a similar sensor there?

The advantage of the Bic pen is that it has an hex shape, so it makes it easier to glue 2 magnets to any two opposite flat surface. But you could just grind flat surfaces on a round tube and get the same results, but the flat surfaces must be perfectly parallel or I assume it might warp the magnetic field.
Even though Al is non-magnetic, I wonder if it does not interfere with a magnetic field.

Allegros A1302 are hard to come by. If I'm not mistaking that part has been discontinued.

(But what was I thinking?? I forgot to congratulate Gene for this nifty mod!!)

Gene, the idea with the bearing... brilliant!