Using arduino to modify output voltage from potentiometer

Projects General Guidance
1

Hi all,

Am new to arduino so I hope this makes senses...

I am trying to wire a PC joystick into my RC plane transmitter so I can fly my planes using the joystick. I have measured the output voltage from the potentiometers in the joystick and the transmitter (I was hoping they would be the same so I could wire the joystick straight into the transmitter but they weren't!)

The simple graph below shows the difference in voltage for the joystick and the transmitter pots, which I assume is due to their different resistor value ranges.

I don't really want to change the potentiometers in the joystick so my challenge is to try and modify the their output voltage which I feed into the transmitter. The modification I need to make is:

If output voltage from joystick pot is greater than 2.47 then multiple by 0.73 else
if output voltage from joystick pot is less than 2.47 then multiple by 1.6

Is this possible using an arduino? If so could anyone point me in the direction of any similar projects or resources?

Or, am I missing a much simpler solution!!??

Many thanks in advance for your help.

Chip

2

There is the map function that may be useful.

3

Voltage divider?
divider.png Or, with trimmers divider2.png

divider.png

divider2.png

4

Put 2 resistors in the leads to the potentiometer. one in the positive lead and one in the negative lead.

This will reduce the voltage range of the pot - no Arduino required

Each resistor wants to be around 2x the resistance of the joystick from your figures.

5

DrChips:
I am trying to wire a PC joystick into my RC plane transmitter so I can fly my planes using the joystick.

Doesn't make any sense to me given the quality of the rc transmitter gimbal would be far superior to any 2 bob game joystick.

Not only that but modifying rc tx in this manner would raise the eyebrows (to say the least) of any rc flight insurance company.

6

JohnLincoln:
Put 2 resistors in the leads to the potentiometer. one in the positive lead and one in the negative lead.

This will reduce the voltage range of the pot - no Arduino required

Each resistor wants to be around 2x the resistance of the joystick from your figures.

Wouldn't this just transpose the joystick line on the graph above down on the vertical axis?

7

DrChips:
Wouldn't this just transpose the joystick line on the graph above down on the vertical axis?

Did you even bother to look at map like #1 suggested..??

8

Study the map() function.

example:
value = (analogRead(A0), 100, 920, 300, 710);

constrain() might be needed to keep values within boundaries.
leo..

9

DrChips:
I am trying to wire a PC joystick into my RC plane transmitter so I can fly my planes using the joystick. I have measured the output voltage from the potentiometers in the joystick and the transmitter (I was hoping they would be the same so I could wire the joystick straight into the transmitter but they weren't!)

[....]

I don't really want to change the potentiometers in the joystick so my challenge is to try and modify the their output voltage which I feed into the transmitter. The modification I need to make is:

[...]

Is this possible using an arduino? If so could anyone point me in the direction of any similar projects or resources?

Starting at the bottom.

NO an Arduino cannot do what you want. Potentiometers are analog devices and Arduinos are digital devices.

If you don't want to modify the Tx pots then I wonder how you have obtained your graph. Without disconnecting the pot inside the Tx and replacing it with another pot there is no way to know what the effect will be.

...R

PS ... you probably could build a complex solution with an Arduino but it would inevitably require replacing the existing potentiometer in the Tx.