Arduino RC Car

Judd · June 22, 2019

So, long story short, I am building an RC car using an Arduino and I have been using an L298N dual H-Bridge motor controller that can handle 2 amps per channel, and I have been using 2 of these motors. On Amazon, the motors say that they are up to 24v, and 0.6 amps each. This led me to believe that the L298N driver would be perfectly fine, but when I got the motors and realized how powerful they were, I figured I would need to make sure.

I hooked it up to a 20v power supply and let them run. No load they draw 0.15 amps each. When I stall them however, they pull 2 amps each. Keep in mind this is only at 20v, so I did a little calculating and at 24v it would pull roughly 2.5 amps, above the controller limit. So, now I am looking for more powerful controllers. I have found a couple on Amazon, first, second, third, and fourth. I would like to stay on Amazon because I have always received everything to order and in a reasonable time, but I could go to a different site if I need to. The only requirements I have are: 3 amp per channel, up to 24v, and the ability to receive a pwm signal and control the motor accordingly (the L298N drivers use 1 pwm and 2 digital per motor, the digital control the direction). I am planning on putting these heatsinks on the drivers, along with these fans blowing across the whole board as the Arduino will be mounted right behind it and there will be 2 intake and 2 exhaust fans for the rectangular case I am 3d printing. And yes I know that brushless motors are what I should be using, along with an ESC, but I don't have the money for that yet and I already had 1 motor and the L298N drivers. But I do plan on using some brushless motors in the future.

If somebody could help me determine the best controller, that would be greatly appreciated. At the moment, I am leaning toward the first one for the (what appears to be) bigger mosfets and pads which I think would help with high current application. Also, I am thinking about the consequences of the motor producing energy and it returning back to the controller, say when the car goes down a hill the motors are spinning and sending electricity back. Will this be a problem? If so, how could I prevent it? Maybe by using the digital signals on the controller I can tell it to put it in a state similar to nuetral in a car?

Also, if anybody is interested, I would be happy to share the code and the 3d files to print so that you could make your own, but it isn't done yet. I still have to get the controller, make a gearbox to increase the rpm from 1000 to 9000rpm, design and 3d print wheels, and design and 3d print the enclosure. Other than that though I'm done lol. Thanks in advance for any help you can provide.

akio123008 · June 26, 2019

First of all, consider passive cooling for the controllers. If you position them cleverly, as they are on a moving vehicle, you won't need those fans. I've got a home made electric bicycle powered by a massive 3kw outrunner and a 150A ESC, and both the motor and ESC are completely passively cooled, so I suspect a +- 50 watt motor/controller combo should be fine too.

On 6/23/2019 at 1:15 AM, Judd said:

Also, I am thinking about the consequences of the motor producing energy and it returning back to the controller, say when the car goes down a hill the motors are spinning and sending electricity back. Will this be a problem? If so, how could I prevent it? Maybe by using the digital signals on the controller I can tell it to put it in a state similar to nuetral in a car?

I don't think you have to worry about that; the motors you're using are geared down quite a bit. It probably takes some force to turn them manually. I'm not sure if you've already tested this, but I suspect that when the car is driving, and you turn off the motors, the drive wheels will just lock up because there isn't enough traction (and inertia as the car is probably not very heavy) to turn the motor drive shafts.

Edit: even if it does, I don't think it would be harmful to the controller.

On 6/23/2019 at 1:15 AM, Judd said:

make a gearbox to increase the rpm from 1000 to 9000rpm, design and 3d print wheels, and design and 3d print the enclosure. Other than that though I'm done lol. Thanks in advance for any help you can provide.

Making a gearbox isn't a very simple thing to do, but more importantly, it reduces the efficiency and it will probably wear over time, need maintanance etc. If you want the car to go fast, wouldn't it be easier to just make the wheels bigger?

Edit: how fast does it actually need to go?