I am trying to figure out a way to take over control of a UDI 818a quadcopter transmitter with an arduino. My thought is to have the PWM pins of an arduino take over the joystick outputs to/on the transmitter. The joysticks in the transmitter look like the thumb joysticks (COM-09032). I’m thinking of just unsoldering the joysticks and soldering in some jumper leads in place and connecting to the arduino PMW pins. I haven’t varified the voltages of the joysticks yet, but asuming they are 5V Vcc anyone see problem with my plan? Would I have to put a resistor between Vcc and Ground on the transmitter or just leave it open? Would I need a resistor on the PWMs to ground? (Yes this is my first attempt at a hardware hack)
ASSuming you’re correct re: the joystick output, you should put a low pass filter btw the PWM pin and the Xmitter input. That might be as simple as a resistor and capacitor.
If you want to generate 0-5V using PWM you will need a Low Pass Filter, but make sure that the PWM is running at a reasonably high rate (at least 10kHz).
Disconnect the joystick wiper to expose the ADC input of the unit. Connect the ADC input to ground with 0.1uF, then connect the PWM to the ADC input using 10k ohms. This gives a (very rough) corner frequency of 200Hz, which hopefully won’t have too much 10kHz ripple on it.
Also the 200Hz LPF will hopefully not slow down response time of the control system.
Thank You… both. I forgot the PWM stands for PULSE width modulated… I just started thinking of them as an analogy signal do to the ~. Thank you for the leads on the filters. I will update once I get the parts in and give it a try.