Using Arduino to read output voltage of power wheels motor

Using Arduino Project Guidance
1

Hello,

I want to convert my kids power wheels car to use hoverboard motors. Going from brushed to brushless. I want to keep the car as "stock" for the kids as I can, original shifter, pedal, and remote control. The best way I can figure out on how to do this is to use an Arduino to read the dc voltage going to the original motors. Convert that to a pwm signal that goes to a motor controller. The car has 3 forward speeds, voltages are 24/12/6 and a slow 6v reverse.

I know I cannot connect to the Arduino without using a voltage dividing circuit but my only question is when it comes to the reverse polarity of the "reverse" selection on the cars original shifter. When I put the car in reverse it just reverses polarity to the stock brushed motors. My understanding is the Arduino needs a ground and a positive lead for the analog inputs but can it read negative voltages? On that note how would the voltage divider behave if we reversed polarities?

Thanks for any advice and for just letting me get this out there.

2

Could I use diodes to isolate the reverse polarity and map it to another input and just use that as a signal to tell the bldc motor to reverse?

3

Just replace the RX and TX, use decent RC componts and you'l be fine. Do ong what you want to do requires some decent electronic hacking skills ...

4

I think you need to know more about how the existing motors are powered. The usual way would be a H bridge and PWM, meaning that the voltage you are measuring is an average. Do you have access to an oscilloscope?

Measuring the reversed voltage is not just a matter of some diodes, but without more information I can't really help more.

Find out how it's actually powered and how the speed is controlled. A schematic of the current arrangements would help.

5

Are you familiar with the mechanism (said in the above quote @PerryBebbington) of that uses a unipolar voltage source (say +12V) to change the motion of a moving car from forward to backward and then to forward? If yes, then I don't need to present the description/schematics; else, I will try.

6

Sadly, no access to an oscilloscope. I did find the circuit board online through eBay but they all lack any schematics. 24V 5 Pin Control Box Receiver Children Electric Car 2.4G Bluetooth Transmitter | eBay

I have the 7 pin version of this. I doubt you can tell based on the picture alone.

Thanks for the response and ruling out using diodes.

7

How do I add a speed selector and pedal for the kids to use in the car?

My original thought was to go rc tx/rx route but I couldn't figure this part out...

8

Oh ... in that case I do not think that you have anywhere enough knowledge to go the arduino route. Get a RX/TX set with one servo and a BL speed controller and replace all the parts inside the toy car. You'd need a mechanically matching inrunner BL motor in the first place, which is a challenge to find. To sum it up: don't touch the toy car if you want your children to be able to play with it in the forseeable future :slight_smile:

9

Sorry, I don't have any further suggestions. I will continue reading replies to this topic and if I think of anything useful I'll reply.

10

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