I am looking for advice on how to make a relatively simple mod of a standard toy RC car, which currently has forward/backward and left/right steering controls activated via a 2.4GHz wireless pistol transmitter.

I believe the car battery voltage (~10V when fully charged) is transferred directly to the motor & steering inputs, hence the car only runs at *full* speed (FWD/REV) or makes *full* turns (L/R steering)


Question is: how can I modify the circuit to enable proportional (to voltage) motor speeds and steering? I would like to be able to try both of the below options (both transmitting wirelessly at 2.4GHz), preferably using the existing motor driver (MX1919):

Option 1) Control the speed and steering via an app that talks to an on-board NodeMCU/ESP8266

Option 2) Control speed/steering using my Turnigy 9X transmitter and its on-board PWM receiver (which outputs PWM from 5 to 10% duty cycle range at 5V full rail)


It appears (from testing of the control board), that if I place a variable voltage between 5 to 10V directly from battery power to the motor & steering input terminals, I am able to achieve proportional control. I have an Arduino Uno and other components - transistors, caps, resistors, relays, etc. that I can use for either option above if required. Of course, minimizing the no.of these additional components is preferred, in order to maintain the compactness of the car design.


A schematic or fritzing circuit for the 2 options would be most helpful and appreciated. I can probably figure out the coding/SW part, but any relevant links there would be helpful too.


Thanks!

Sam