FMS Forum

by **astrogav** » Sun Mar 17, 2002 8:45 am

Thats how mine was setup steve. Works ok but way too touchy. when calibrating you can see the problem as the indicators on screen only move a fraction for full movement of controlls.

by **Rockfist Rogan** » Sun Mar 17, 2002 2:01 pm

Ok, so here's the bad news

The old Tx I planned to change the pots on is a Futaba Challenger FP-T6NL. I attacked the right hand gimbal to extract the elevator pot...

It's VERY small, The *body* of it is 13mm diameter x 4.5mm thick, and the (unthreaded) neck is 6mm diameter x 4.5 long.
The shaft has NO flats and is 3.5mm diameter x 10mm long.
The pot value is 5k linear. No wonder it didn't work too well! The trimpot measured 10k.

I have unearthed one of the *small* Maplin pots, (wrong value, anyway...) and there's no way it's going to fit. Much too big!

I then hunted in my *bits* box, and found 4 x 500k pots with *CTS 7747* on the back. Although these are somewhat smaller than the Maplin pot, they *still* won't go in without major surgery on the gimbal. I think any attempt to fit them would finish up with everything in the bin.

So, if anyone finds a source (in the UK) for 500k or 470k pots of the CORRECT size, please let me/us know! The existing 10k trimpots may just do their original job ok.

RR

by **johnhlong** » Sun Mar 17, 2002 4:05 pm

This might be a bit late or maybe unnecessary but did you go the the control pannel and run the calibration setup for the joystic there before running the calibration in FMS? :0

Just wondering if that might help tame things down.

John

by **Rockfist Rogan** » Sun Mar 17, 2002 7:28 pm

Yes, I did john.
I tried every darn thing I could think of in fact!

It *did* work, but not consistently enough to be viable. I was forever trying to recalbrate it. If I can't find suitable pots, I'll give up with it.
As I mentioned before, correct trim adjustment is as important with sims as it is with real aeroplanes, either models or full size.
I have no problem with trimming using the*other* Tx (with a 2 transistor interface), BTW. That works fine, but only with FMS of course. (grrrrrrrr)

If I can't set a Tx up so that the model virtually flies itself without my interferance, something isn't right.
Ok, not the Pitts Special maybe, but the DG1000 shouldn't be too difficult, should it?

I just had a thought...wouldn't it be great if we could click *on-screen* trims with the mouse? ...and maybe even play around with the CG! Hmmmmm.....

RR

by **heliphil50** » Sun Mar 17, 2002 11:01 pm

I use a Futaba FF6. I used to have it on a serial port but suffered with lots of interference. I have now changed to a Ripmax joystick interface and hey presto perfect flying no gliches and so easy to install

by **johnhlong** » Mon Mar 18, 2002 12:31 am

I use Ken's joystick interface (from England) and also have wonderful results.

I built his kit for about $15.00 - $19.00

John

by **Rockfist Rogan** » Mon Mar 18, 2002 8:31 am

Yes, they are excellent!
My mate has the PIC version and it works really well.
It doesn't work with CFS or FS though...

RR

by **Steve Lewin** » Mon Mar 18, 2002 9:09 am

You'll find that Ken's *JOYSTICK* kit (http://www.welwyn.demon.co.uk/joystick/joystick.htm) certainly does work with FS/CFS, I've tried it. So does the Ripmax interface. Anything which connects to the gameport will.

BTW have you tried RS Components for the pots (http://rswww.com) ? They generally have a much wider range than Maplin and they are happy to deal with the general public (provided they have credit cards

). Excellent service but a bit pricey.

Steve

by **Rockfist Rogan** » Mon Mar 18, 2002 4:29 pm

Confusion reigns....
My friends PIC interface came from Custom Electronics:

We couldn't make it work with CFS + FS. Should it?

RR

by **Rockfist Rogan** » Thu Mar 21, 2002 8:52 pm

by **Rockfist Rogan** » Sun Mar 24, 2002 9:14 am

Can nobody help with the above????

RR

by **johnhlong** » Sun Mar 24, 2002 9:42 pm

Here comes the answers to the questions

(1) The pots are 500k, and of this I get 120 k over the limited travel of the stick(s). OK so far?

With the shaft central, I get:
190k (unused) then120k used, and then 190k (never used)

Or should I position the shaft at one end to give:
0 to 120k with 380k never used.

I think the latter must be the way, but I need confirmation, please. (0 at the *earthy* end? (pin1))

I measured an actual joystick and I get the range of 0 - 94k. Stick to the 0 - 120k and see what happens.

(2) I also want to keep in series (?) the existing 10k trimmer pots. Would these go between the *earthy* end of the main pot(s) and pin 1, or the other end?

doesn't matter if since they will be in series. Just for sanity sake I would put them on the signal side.

(3) Do I need an additional fixed resistor(s) in series (or one common one at pin 1) for safety (of the computer...)?

If you put a resistor in series you would shift the working range of the setup. Since the working range of a real joystick is 0 (shorted) to 100k / open, and the device doesn't have any voltage from it the additional resistor is unnecessary.

Suggestion:
I would put a resistor in parallel to your pots. A resistor there would lower the overall top resistance of the range of your pot movement. Start by selecting a resistor that would change the output of your pots to 0 - 90k. Then add the 10k trimmer pot in series between the new duel resistor circuit and the interface pins.

R1 R2
Pin 1 ----------+------/\/\/\/\/----+----/\/\/\/\/--- Pin 3
| |
| |
| R3 |
+-----/\/\/\/\/ |
^ |
| |
+--------+

R1 = New parallel resistor (Select size by experimentation)
R2 = 10k trimmer resistor
R3 = 500k adjustable resistor.

This should give you a range of 0 - 100k (Including trimmer adjustment) with the ability to trim the center position from 45k - 55k.

John

by **Rockfist Rogan** » Mon Mar 25, 2002 10:06 am

Thank you *so* much John!
It was really kind of you to go to all that trouble.

I'll let you/everyone know how it works.
(It might be a couple of days...)

RR

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