RC Toy Car Conversion to Hobby Grade. Bluetooth Mobile App Control With Proportional Steering and Speed.

In this project, I'm converting an RC toy car that I owned as a kid into a hobby grade car. This car can be controlled with an android application via bluetooth. It has all the features of a car like front - rear lights, horn, neon lights which are controllable via the app. It also has an emergency feature that stops the car and shuts everything down in case of signal loss.

1. Arduino Nano
2. L298N motor driver module
3. HC-05 or HC-06 bluetooth module
4. Servo motor SG90
5. 2s and 3s battery (Adjustable according to need)
6. A toy RC car (Preferably a bigger one with some space)
7. LEDs(5V) and Buzzer for horn (Optional)

If your car uses servo for steering, you're good. But if it doesn't have a servo, this is the most difficult step where extra care needs to be taken.

You need to make room for the servo in the stock steering mechanism. The servo should be fitted and centered properly for the steering mechanism to work. I have glued the servo on the top housing at just the right spot and height. I have used a piece of steel wire and fixed it with super glue in the servo arm. As you see in the third picture, the wire must be able to stay in the hole in the centre of the steering arm and move the arm from one side to another even after assembling. This process can be different for you according to the steering mechanism of your car.

It doesn't matter if your wheel alignment is a little off as it can be fine tuned in the android app.

I have provided the schematics for the circuit in the above picture. Sorry for the poor design.

The code for the arduino and the necessary libraries is given in the link below.

Copy the libraries to "C:\Users\My Username\Documents\Arduino\libraries"

Rc car.zip - Google Drive

After some research I found that the HC 05 module needs a voltage divider across its Rx pin to match the logic level of the arduino (pics 3,4 and 5 ). However, I didn't have any issues even without making a voltage divider. So this is optional. Still, to be on the safe side, I've included the schematics.

After connecting everything, I have enclosed the electronics in a small enclosure.

The motor driver can heat up pretty bad. It is better to place the motor driver module in a way that there is airflow through the heatsink.

Bluetooth has a very poor range. So it is also better to put the bluetooth module in the open where the signals aren't obstructed. The car is programmed to stop in case of signal loss.

To power the motors, I'm using a 3s(11.1V) battery which is connected to the L298N Vin pin. If you have a motor that requires higher or lower power, you can adjust this.

If your motor requires more current or if your motor struggles to run at low speeds or if the L298N module heats up bad, you can combine two channels of the L298N module as in the pic and get higher current output.

To power the arduino, I'm using a small 2s(3.7V) battery which is connected to the Vin pin of arduino.

I am using separate batteries so that the motor can pull all the current. The voltage regulator in the L298N module also heats a lot when applied higher voltages. Also the circuit seems to randomly shut off during times while being powered from the L298N module.

I did not make this app and I don't own it. It is an amazing app with tons of features. You can download this app from Play Store from the link below.

Bluetooth RC Joystick Controller – Apps on Google Play

Bluetooth RC Joystick Controll APK for Android Download (apkpure.com)

I have not used all the features of this app. There are options to add various sensors like temperature sensor, Battery level sensor, speed, etc and control a tilt pan mounted on the car. I have not used these features. You can get the complete guide for this app on the author's website below.

Bluetooth RC car - 6.Joystick Control (google.com)

First, you need to pair your bluetooth module with your phone from the bluetooth settings, if asked for a password enter 0000 or 1234.

Then you can open the app and in the settings, click on connect to car. Your bluetooth module should be listed there, click on it and the car should be connected.

You can change the speed ranges, steering ranges and the wheel alignment from the "change ranges" option.

There is also an accelerometer mode, you can control the car by tilting your phone.

So after completing the car, I tried to make it look good. I completely ditched the outer cover as the batteries didn't fit. I also added a front nose and a spoiler to make it look like an F1 car. I have included the testing and driving portion in the above video. I hope that my instructable helped you in some way. Thanks for reading.