Hi y'all great flyers

What is a potentiometer in Tx, and what is exponential? What are the pros and cons of those. I have read about exponential that it eases the servo movement and makes your flying more smoother and easier. I have never used exponential infact my radio does not have it. Future radio hopefully is 2.4 Ghz but I'm scared of radio's locked out.

Spektrum is coming out with another great new model of their I think DSM series, has anybody known anything about it. I know it's coming out after 2 months. Sorry topic was different but I also wanted to ask about brand new radio of Spektrum which is being released after 2 months.

Thanks for your input, as I love to learn new things.


Happy flying

Mody

A potentiometer is what translates your stick movement into a digital signal. Its really nothing more than a variable resistor. The stick moves the pot, the pot changes resistance, and a circuit translates that in to where the stick is positioned and encodes it for transmission.

Expo deals with how your servo moves in relation to stick movement. Linear throw if you move the stick half way the servo moves half way.

If you enable expo the servo may only move 25 percent of its throw between center and half stick, then the other 75 percent from half to full throw. The effect is that the center feels softer but you still have full throw if you yank the stick around. Dual rates perform a similar function in that they make the center feel softer and the model more controllable but it sacrafices total throw.

If you want to play with it try 25 percent or so for starters, positive for softer center for JR and negative for Futaba.

You can also achieve the opposite effect making the center very sensitive if you so choose.

As for the lockout stuff, thats rubbish.

Thank you very much for the great explanation Barracudahockey. Never understood the relationship of hockey and barracuda

I have seen couple of videos planes got crashed due to radio locked out and no signals were being trasmitted, even saw a video of turbine crash. Which radio was that I don't know. But The old flying field I used to fly, there was a guy who only flies turbines, his brand new turbine crashed due to radio lock out. and He told us that couple of times his radio locked out, and I guess he was using JR. Which radios have lock out problems?

Two points here:

Though I have never used expo on my models, I have tasted it on the sim. It makes your model react softer as Andy described. I means, if set up correctly, your model will not move in a snap if you put in a lot of movement on the stick. This I am told helps out in models that have the tendency to snap such as wing tip stall or stall with too much elevator. I found that on the 3D models in the sim, expo added a certain lag and slowed down how quickly I corrected in a maneuver eg a hover. Personally, I have never used expo, but then again, I have never used a model that requires it. Most of my models have 3D tendencies and very good low speed handling.

I think you are referring to radio interference. Obviously, in the fixed frequency radios, two people on the same frequency cannot fly together. Solution to that is to go and check with everyone as to what frequency they are flying and locate next to each other on the flight line if you are so you can keep an eye on each other. Alternatively, if you go to 2.4Ghz setup, there is less likelyhood of interference. However, the way to avoid interference we found is to check clear frequencies and not fly with more than 5 airplanes at a time in the sky

Ameyam

Mody,

As BH has explained above, exponential is one of the ways in which your input at the TX reaches the servos.

However, potentiometer is not related to the Tx, but to the servos.
This is an electrical device inside each servo, which tells the electronic brain at what deflection angle the arm of the servo is.
Let's say you command the sevo arm to move 10 degrees clockwise, the motor inside the servo starts rotating the gears and the arm, while the potentiometer is watching the movement; once the arm reaches the 10 degrees, the potentiometer sends a signal to stop the motor and lock it in that position until a new command from you is received.
The potentiometer is also the sensor for centering the servo arm in the neutral position (neutral Tx-Rx signal).

Here you can read additional information on how exponential works:

http://www.rmfm.org/dual_rates_and_exponential1.htm

Here you can see some good pictures of the servo guts, including the potentiometer:

http://www.twf8.ws/new/tech/servos.html

Half true.....

In fact, the Tx's sticks have potentiometers attached to them that interpret the stick's movements. There is a pot for each axis so each stick has two pots connected.

The pots in the TX take the stick input and convert it (in one direction) just as the pots in the servos convert that information (in the opposite direction) into servo arm movement.

That is very true!

I stand corrected.

Guys thank you very much for such a great explanation.

LNEWQBAN> Both links are great I'm gonna read up on that.

ameyam-> Thanks for your sharing, but I have not mentioned or asked anywhere about the interference, as far as 72 Mhz is concerned yes, we have to use the pin boards where every channel's chart is there, so those who are using 72 Mhz they know which frequency is being used on which channel so there is no way of conflict or interference, and it's also verbally asked, and 2.4 Ghz not to worry.

Thank y'all

Mody

Here's a few simple facts.

1. Any electronic equipment can fail. Recievers can die, batteries can short, servos can take a vacation at the worst possible moment etc just like you could blow a tire going down the interstate or your car battery could be dead for no apparent reason.

2. "Many" of the "equipment failures" I've seen (and I've been around RC for a LONG time) have been from either improper installation, or improper operation. Whether or not people will admit to operator error or not is another matter.

3. Lnewqban as Rock said, you're partially correct and since he was asking about expo I assumed transmitter so I went with the stick pots but you're correct, the servo's have pots as well. When I started it was common to take them apart and clean the servo pots with contact cleaner when they started acting nutty

I trashed a 1500 dollar 90 size helicopter once because instead of sitting out flying it a weekend I flew it on nylon gear servos instead of waiting for the metal gear servos I ordered to come in on Monday and I stripped a servo in flight. Was it the servo's fault?

As for the BarracudaHockey, check out page 106 of the May Model Aviation

I feel I misled Armody with my response, sorry.

Yes, the transmitters have four potentiometers inside, one for each axis of control.
When we move the sticks, we are turning these potentiometers.
For mode 2 Tx's, we can move two potentiometers at once (the one that controls ailerons and the on ethat controls elevator) if we move the right stick diagonally, like in a coordinated turn.
The attached pictures show a potentiometer and how they are installed inside the transmitter.

The deflection of the stick produces an output signal that can be lineal or exponential, for transmitters that have that capability.

Congratulations on your interview, Andy![sm=thumbs_up.gif]

BH, da rock, LNEWQBAN

Guys Thank you very much for your explanations and advices. It's great, I got couple of interviews going on, got a job desktop support, waiting on a response from one oil company for their IT networking support and another oil rigging company. I'm so happy economy is picking up, it's good for us, and for our Great Country.

On Sunday could not fly did chit chat at the field all day, wind picked up around 20Mph, it was ok, did not wanna take a risk, but the wind gusts were killer, next sunday and saturday is shower predictions, as I'm also moving to Magnolia, and field is only 4 miles from my new house who could be that much lucky.

Thanks again guys for your great insight. My best wishes to y'all and happy flying

Mody