Backstory

Back in 2016, we were about to bring home our new daughter from India. She has been diagnosed with Caudal Regression Syndrome. In her case, she is actually missing her legs. So when we saw that Power Wheels was about to release their new “Wild Thing” model, we thought it would be great for her to be able to play in the yard with the kids. Of course, the price wasn’t great at the time and we ended up forgetting about it.

Skip ahead a few years later, I’m scrolling through Facebook marketplace (my new guilty pleasure) and I see one posted for $90. It says it is just missing the charger but I know there’s more risk than that so I ask if they’ll take $50…long story short, they message back a week later saying they would! I get it home, battery tests fine, I charge it up and…**insert sad face**…nothing.

I had planned pretty much from the get go to throw some sort of an Arduino in the little guy so I got pretty adventurous reverse engineering the thing to see if I could figure out what was wrong. Turns out that the gyros in the handle controls weren’t communicating right…that was about as far as I got though.

Some NodeMCU Learnings

Turns out the PWM signal is handled a little differently than a regular Arduino. Found a great read on Henry’s Bench that explains a whole lot more in detail about this but long story short, it isn’t just 0 to 255 for the analog out…it goes up to 1023.

Also, the digital read goes through ground and not 3.3v. You can read the notes in the code to see more of my findings are which pins should go through ground and which should go through 3.3v.

The Build

For the electronics, I went with a couple BTS790s for the motor controllers and a NodeMCU for the core board. I like the NodeMCU because they’re crazy cheap and they have the ESP wifi chip build in…so they make a great little IoT board if you ask me!

I liked they’re original hand controls so all I did was cut the ends of their existing wires and soldered them right to the spring inside! So no speed control for the handles but makes it super easy to integrate.

Sorry but I don’t have a wiring diagram for this (yet!) so you’ll have to look at the code on how to get it wired. I just had the hand controls share a ground pin and the motor controllers in various PWM pins. Nothing too complicated.

What was weird on the BTS7960s was that they each take two PWM pins, one for the forward signal and one for the reverse signal…I don’t have much experience with high amp motor controllers but I thought this was odd…why not just a high or low pin to tell you forward or reverse…?

You can find my code here: https://github.com/iceman198/nodewheels You’ll see that it puts out a little hot spot signal. As soon as you load the web page on your device, it disables the controls for the kid in the machine. I just thought this was a fun feature to add on.

Now to hook my lawn mower up to it!

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