September 3, 2016

Receiver upgrade WLToys A979

This is my only build this summer. With two small kids and a 120 year old house, well, I hope this is a low mark in hobby time...

Anyway. I always wanted to replace the transmitter that came with the WLToys A979 that I got for my eldest son. For two major reasons and many minor. First off I hate RTF radios as they occupy what little space I have in my hobby corner. Secondly, I wanted to be able to make adjustments to make it easier for my son to play with the car, such as capping the throttle and adding some expo to the steering. The intention is of course to use my Futaba 4PLS as radio.

You cannot just replace to receiver in this car to achieve this. It is equipped with a 3-in-1 electronics unit which contains receiver. ESC and servo controller. Servo controller? Yes, it has a 5-wire servo which is a servo without electronics itself. Instead the two extra cables are connected to the potentiometer in the servo and the controller electronics is in the 3-in-1 unit. This is a shocker to me, but apparently the chineese like it this way. In essence it means that you need to replace everything. Well, you can keep the motor.

It took me some time to get the right stuff. I thought I had a servo that would fit so I only ordered receiver and ESC. But at the bench I realized I didn't have a proper servo. So I figured out which one to get, ordered that, waited. And then I put everything together. But silly me got it all wrong, I though I could use any brushed ESC and just get the programming right. But nope, you cannot use a brushed ESC made for airplanes in a car. It won't break (on command). It won't reverse. And it won't accept mid-stick as neutral. Even the fanciest of remote controls will help you! So I had to order another ESC. And finally.

The parts

So. The ESC is speced at 320A. Yes. It might be true, but I would not bet on it. It fits perfectly in the car. It works. I'm probably pulling about 10A with my setup, so I won't bother with the specs.

As to the servo. I spent some time to find this one. In fact, I found it as spare parts for this car at a site online. They had done a mediocre attempt at hiding which servo model it actually is. Didn't take me too long to figure out. This one is perfect for the car, no mods needed.

The build

Not that much to say about the build. Hook the stuff up. Replace the power connector with a JST connector if you wish to use the original battery. Find a good location for the receiver which will have no natural place in the car as it was originally part of the 3-in-1 unit. Cables, yes, there will be surplus cables. In the picture below you can see all the cables, and you cannot see the receiver, because of all the cables. The serious modeler would of course shorten those cables to make it more tidy.

A979 new ESC

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