RC transmitter Joystick circuit

I am trying to control my RC plane with arduino instead of the transmitter. I will need some digital potentiometers to replace the joysticks....I don't know though of what PCB pins of the joysticks I must solder the digital pots too or how joysticks pots work.

I don't know too much about hardware but I opened up my transmitter and took some pics in hopes that someone here can help me out.

I got a digital multi-meter and measured those 3 solder pins on the PCB and got 3.3 V. I don't know what was going on in the PCB but probing the region at the joystick's location gave 3.3V so it must mean the logic level TX operates on is 3.3 V. Each joystick can move up/down/left/right. Do I need 4 digital pots? What valued pots and resistors do I need to simulate the joysticks with arduino?

Here is the attached pics:

http://i.imgur.com/KucYwT7.jpg http://i.imgur.com/7AKSXwd.jpg http://i.imgur.com/2oYrcSm.jpg http://i.imgur.com/mkbUPbZ.jpg http://i.imgur.com/4b5whUI.jpg http://i.imgur.com/TFKqssS.jpg

Here are all the pictures in an easy-to-view album: http://imgur.com/a/4hD7B

Joystick pots are just ordinary potentiometers; simple voltage dividers. Why do you think you need digital pots?

Very difficult method to accomplish the task. Best method is to utilize R/C radio transmitter that has a 'trainer port' and utilize PPM serial data to send directly out to the R/C receiver, bypassing all the analog voltage conversion hardware and much software.

Lefty

I need digital pots because I don't want to use the joysticks to control the rc plane..I want to use arduino instead. Arduino can't control the joysticks unless I put some servo to mechanically turn the sticks but isn't it much better if I use digital pots?

Should I just buy some stepper motors and use those instead to mechanically control the transmitter? Normal pots have 3 leads so if you have 2 pots then you should have 6 leads but the joystick pots I see on google have more than 6 leads so I can't tell what is going on... But I can't tell on the PCB where the leads for each pot are and how the joystick pot system works.

I posted this earlier in the hardware section but didn't get any responses so I thought that this might be a more suitable place to ask this question.

I am trying to control my RC plane with arduino instead of the transmitter. I will need some digital potentiometers to replace the joysticks....I don't know though of what PCB pins of the joysticks I must solder the digital pots to or how joysticks pots work.

I don't know too much about hardware but I opened up my transmitter and took some pics in hopes that someone here can help me out.

I got a digital multi-meter and measured those 3 solder pins on the PCB and got 3.3 V. I don't know what was going on in the PCB but probing the region at the joystick's location gave 3.3V so it must mean the logic level TX operates on is 3.3 V. Each joystick can move up/down/left/right. Do I need 4 digital pots? What valued pots and resistors do I need to simulate the joysticks with arduino?

Here is the attached pics:

http://i.imgur.com/KucYwT7.jpg http://i.imgur.com/7AKSXwd.jpg http://i.imgur.com/2oYrcSm.jpg http://i.imgur.com/mkbUPbZ.jpg http://i.imgur.com/4b5whUI.jpg http://i.imgur.com/TFKqssS.jpg

Here are all the pictures in an easy-to-view album: http://imgur.com/a/4hD7B

I posted this earlier in the hardware section but didn't get any responses

Cross-post merged.

DO NOT CROSS-POST, IT WASTES TIME.

I have 4 potentiometers but I want to use arduino instead to control a circuit I have that is currently controlled by these pots. These pots operate from 0V-3.3V. How can I control all 4 using arduino uno?

Is there a way to do PWM with 3.3 v? I would need to do this PWM for the 4 pots if it is possible.

Please help people to help you. Attach some graphic of your circuit so we can understand what you re after

Here is the circuit:

The yellow circles I have circled are the pot's output and brown is GND and RED is 3.3 V . Instead of these pots, I would like to solder onto the input hole where the current pot's output goes to.

Should I just stick the Arduino's PWM pins at the place where the pot's output is to simulate input voltage between 0-3.3 V?

The problem with potentiometers in an existing circuit is that you don't know if they are acting as voltage dividers or as variable resistors controlling current or some time constant. So advice is hard to give unless you provide some more info

I believe they are acting as voltage dividers in this circuit because this pot is in a transmitter of a remote control car. This pot is a joystick which control's the rc car's speed and the other pot controls direction.

The pot operates between 0 and 3.3 V so I need to use the arduino to simulate this pot...What can I do to simulate it? Maybe use PWM and a low pass filter? Joystick at middle position gives a 1.67 V after I measured with a DMM and fully pushed gives 3.3V.

If low pass filter is a good option then what values should I get for the R and C values?

It sounds as if you have measured the voltages and confirmed that the pots are being used as voltage dividers, but if you haven't made sure then you need to do that.

It's possible to get digital pots which behave similarly from the point of view of the circuit but can be controlled electronically.

If the end terminals of the pot are at fixed voltages and it's only being used as a variable voltage source then you could use a DAC (or make a DIY version using PWM and an external smoothing circuit) to replace it. Depending what the circuit is doing with your voltage, it may be absolutely essential that it is smoothed perfectly, or smoothing may not be necessary at all.

AHA! @PeterH, That is what I just read about online and was looking at the PWM but I can't figure out what values to use for resistance and capacitance to make the Low Pass Filter. The voltage divider varies between 0-3.3 V depending on the joystick's position. I don't know if I should get a digital Pot or use the PWM with low pass filter. In either case I don't know what values of resistance I need to make the circuit work.

EDIT: I don't know what values of R and C will give me the quickest stability but for now I am going to try 47 uF and 1k Ohm.

I hope this will be a decent LPF. One problem now: I have to use 4 PWM pins with each ranging from 0V-3.3V so can my arduino UNO really support 3.3V*4 ~ 13V? What can I do? I guess MAYBE through programming I could keep only 1 PWM on at a time but is there a better solution?

I just spent 12 hours resoldering and trying the Low Pass filter method and I soldered the Low pass filter input to the pot's analog output, nothing happened other than the transmitter giving me ???? marks....So now I am just going to put some servo/stepper motors to mechanically control the joysticks...Can someone guide me on how I should set up the servos/stepper so that each joystick can be controlled in the 4 directions?

Wouldn't it be easier to go for the digital potentiometer solution?

nilton61: Wouldn't it be easier to go for the digital potentiometer solution?

I guess I will try that next. What circuit do I need? I can find some digital pots online but I really need help with making the circuit...Also, should I go for servos or stepper motors or servo with encoders? I need decent accuracy but not hair width accuracy...There is a small problem which may be a cause of why my LPF PWM approach failed...The pots on the PCB are bent from some of the areas and even after de-soldering the contacts I couldn't get the pots removed from PCB because one of the leads are bent to clamp on to the PCB.

So I am guessing I can try the digital pot apporach or go with a fail-safe approach of using servo or stepper motor to do the job..Then I will have to buy plastic gear and mount the stuff to control the joystick which is a pain...

First if all they should have about the right value. Take some time and study the data-sheets. Most have some serial kind of interface like spi or i2c. You should go for these and not the increment/decrement type. There are also libraries for the communication. The ic's have the same connection as a normal pot a,b and wiper. I recommend do some experimenting and bench testing before connecting them to the equipment, that minimizes the number of things that can wrong at a given time

nilton61: First if all they should have about the right value. Take some time and study the data-sheets. Most have some serial kind of interface like spi or i2c. You should go for these and not the increment/decrement type. There are also libraries for the communication. The ic's have the same connection as a normal pot a,b and wiper. I recommend do some experimenting and bench testing before connecting them to the equipment, that minimizes the number of things that can wrong at a given time

I don't know much about the digital pots but from what you said it seems to me like there are 2 types of digital pots: ones that instantly change their resistance and others that transition before hitting the target resistance. If I am simulating the joysticks then wouldn't the increment decrements be better for this case? I need something that operates on 0-3.3 V to make this work.