Search for Replacement 9x Potentiometers!

[Flaps 30]

Hopefully just changing one pot wouldn't require changing the 5 Volt regulator.

Anyways. Latest information on the use of a hall effect device as a replacement for the joystick pots.

Take one perfectly good (new) 9X and rip out one of the pots.

Rip out the innards of the pot and add that to the collection, along with the small PCB. The new additions are the Allegro A1302 and one diametrically magnetized cylinder.

Place the diametrically magnetized cylinder on the remaining steel parts of the rotor to see how easy it would be to adjust position/centralise and rotate it.. No problem at all.

Assemble parts for testing.

This was the testing stage. The red line on the magnet marks the area of minimum magnetic force, hence the mid voltage reading on the meter.

It was fairly easy (albiet fiddly) to adjust the position of the magnet. As you can see, nothing at this stage is glued in position. The gap between the magnet and the sensor was such that you could get two sheets of paper through the gap.

The output voltages from this was pretty good. Worst case was Max=4.80 Volts Min=0.25 Volts and that was without trying too hard. Best case was Max=4.90 Volts Min=0.16 Volts.

It all seemed fairly linear. Probably thanks can be given to the diametrically magnetized cylinder for that, all other attempts at using 'normal' magnets failed regardless of what I did to improve the linearity. That included using a couple of magnets with a shorting bar. It was close, but it was too big to fit into the pot..

Magnets used -----> http://www.ebay.co.uk/itm/6mm-dia-x-4mm ... 4ab0ea4144

For anyone here that is desperate for a good potentiometer resistance track. Please PM me.

[jhsa]

great work.. question, how did you (or planning to) mount the little board with the sensor?

João

[Flaps 30]

With the aid of the 22SWG wire (as shown and some epoxy resin the board will be glued to the potentiometer case. Glue is drying at this time. A small blob of epoxy will keep the magnet located, when I have finished more tests.

The other potentiometer with the square board will be given the same treatment.

Note that the connections to the board are not as they were originally. They have been changed to accommodate the sensors arrangement which is +V, 0V, Output (equivalent to the slider)

[jhsa]

good, can't wait for your tests and results..
another question, the voltages you've mentioned were measured within the stick travel, right?
That would be great as we would have full resolution without the aid of other circuitry..

João

[Flaps 30]

Yes. The voltages shown where taken with the pot mounted in the gimbal as per the last picture. I should have taken a measurement of the original potentiometer voltages before pulling it all apart. Anyone have the voltages for that?

[jhsa]

fantastic.. I would say that the voltages you measured are good..
Do you have a source for the magnets? and the sensor? I might need to open my radios soon to update the sd card
Thanks

João

[Flaps 30]

The magnets used/source -------> http://www.ebay.co.uk/itm/6mm-dia-x-4mm ... 7137199730

Sensors (I bought a pack of ten from them) are here ----> http://www.ebay.co.uk/itm/2pcs-Original ... 3cca58f179

[Kilrah]

Cool!
Last step is to check linearity by plotting many stick angle/output voltage points...
End points are a good start, but if it takes 3 hours to align the magnet so that stick travel is regular it might get complicated

[Flaps 30]

Cheers Kilrah. You have got the job to do that.

It seemed linear enough to my fingers and what was coming up on the meter. Sure if the magnet is off axis, then you will end up with linearity being something other than linear. But how much does it really matter for what we are doing if there is a small(ish) error?

Looking at what I have at this time. I can see that the magnet is not central, which is giving some compression at the ends, as the distance between the magnet and the sensor is greater at the ends.

[jhsa]

but how much compression? is it noticeable?

[Kilrah]

But how much does it really matter for what we are doing if there is a small(ish) error?

It depends how small "smallish" is
If it becomes equivalent to having 30% expo it could become an issue... hence the interest in quantizing it

[Flaps 30]

No the compression isn't noticeable.

Kilrah -I didn't notice anything that would cause any problems. If it did. I would be saying that the hall effect idea was dead. Yes it does require you to take some care on ensuring that the alignment is as close to perfect as possible. That is no different to the previous hall effect experiment.

Tomorrow I will have time to do final checks, and I will be looking closer at such things as linearity and temperature stability.

[jhsa]

they want 10 pound postage for the magnets to Germany.. that could be the price of an entire gimbal

Would neodymium work?

[Flaps 30]

Would neodymium work?

The temperature coefficent/stabilty of that material is not as good as Samarium Cobalt. If that makes any practical difference in this case I wouldn't know. Perfectionists would say it does.

The magic part of what the magnet is about is this the fact that it is a diametrically magnetised cylinder. The power of it from my findings would have to equal the magnet I used, and ideally be the same or a couple of millimetres more in diameter. I am assuming here that you would be looking at doing it the same way as I have.

You could always go the whole hog and build your own assembly. Something like the one below looks good.

[Spoogy]

How about the potentiometer made by Namco with part number: VG75-03824-00. Is that any good? -> http://www.namcoparts.com/ecommerce/Cat ... px?IID=662


And these are all 60 degrees -> http://www.digikey.fi/scripts/dksearch/ ... tm=0&fid=0

[sokolum]

Question and maybe not the right thread... But 1 of my knob pots (there are three) is half defective... at the center it doesn't work, only at the both ends.
Any idea where to buy a new pot (actually want to buy three new ones, just to b sure)?

[kaos]

Just come across this :
http://www.hobbyking.com/hobbyking/stor ... ode_1.html
http://www.hobbyking.com/hobbyking/stor ... ode_2.html
http://www.hobbyking.com/hobbyking/stor ... ode_2.html

may be useful for whole gimbal replacement or potentiometer.

are these compatible with T9X?

[bob195558]

I also saw this at Hobby King. Replacement Parts for the 9XR Radio:

http://www.hobbyking.com/hobbyking/stor ... source=EDM


I have order 1 of each, Left and Right Mode 2 Gimbals, to verify that they can be used with our 9X Radios.
Orders from Hobby King in the past have taken 3 to 5 weeks of shipping time before I have received them.

The cost of each gimbal was under $5 and shipping was around $10 and
HK says these items have been shipped.

Today I think many of these 9XR replacement parts, are now on back-order at HK.

From the pictures, at HK, the 9XR Potentiometers look like they are the same as our 9X Radio Potentiometers.
Some of the, HK Discussion, says that the gimbals will not drop in without some modifications and
that the Potentiometers are the same parts and will fit in our 9X Radios.

I also ordered 1 of the 9XR Main Boards to see if it could be used with our 9X Radios too. The cost was under $7 for the 9XR Main Boards.

The wiring plugs on the 9XR Replacement Parts will need to be modified to be able to work with our 9x Radios,
these replacement parts have not been designed to be used with our 9X Radios.

Even if this becomes a source to obtain replacement carbon Potentiometers for our 9X Radios,
I still hope the work on replacing these unreliable carbon Potentiometers with a Hall Effect device will continue.
I believe the Hall Effect is a much better and reliable way to build RC Gimbal Controls.

http://simhq.com/forum/ubbthreads.php/t ... bal_design

http://hackaday.com/2012/02/14/improvin ... t-sensors/

http://www.diydrones.com/profiles/blogs ... nt-sensors

[kaos]

any one knows if the 9XR potinator /gimbal can be used for T9X? sort of remember read about that but can't remember. I see the main board for 9XR is a part, 9XR comes with M128 right? Can we swap the T9X main board with the 9XR Main board?

[SkyNorth]

The 9XR board and the 9X board are software compatible , not hardware compatible.
The mounting screws , and switch locations are different , as is the LCD and connections.
-Brent

[kaos]

Thx Skynorth.
so we can't use the potentiator/gimbal from 9XR on the T9X??
But I think we can use the pots and switches?

[mpjf01]

The pots in the 9XR replacement gymbals that I just received are marked as 80 degrees rather than the 60 degrees in the 9x (unless it's a temperature measurement). 5k ohm. I will check if the pots actually fit the 9x gymbals in a day or so.

[Flaps 30]

Hmmm.... That will create a huge lose of resolution when compared to the 60 degree pots. I wonder how the 9XR overcomes this?

[jhsa]

It doesn't

[MikeB]

Just by the calibration. Their gimbals are different, I don't think they have a D on the pot shaft, so using 80 degree pots makes it easier to setup.

Mike.

[Flaps 30]

Thanks Mike. So they just make do and accept that their TX has poor stick resolution when compared to the 9X. That will please the purists who see the loss of even twenty steps of resolution as being a total disaster, and their nice model(s) will never fly as well using the 9XR. Gosh!

[MikeB]

Looks to me like about 1300 A2D counts from end to end.

Mike.

[mpjf01]

Photos of the 9XR replacement pots.

[jhsa]

the resolution won't decrease if the stick uses the full 80 degrees of the pot. But does it?

[Flaps 30]

If the full range (80 Degrees) of the stick is used. Then there isn't a problem. Anything less is a disaster for some.

The pot does look the same as the original 9x ones it has the same B502 stamped on them, the difference is the 80 instead of 60.

I have done a resistance measurement with the old pot. Pot track resistance is 4.92K (note that on another 9x I have it is 2.5K)

Stick centre=3.5K
Stick at end =0.16K
Other end = 5.33K... - Yes that is 5.33K and not near the 4.92K.. I assume that this is due to the resistance of the centre wiper track.

To me it made more sense to do a voltage measurement instead.

Supply voltage=10.0 Volts
Centre=4.74 Volts
End=0 Volts
Other end=9.45

It would be interesting to see how the 9XR pots compare.