Need help powering robot

Help & Support Robot Parts
1

Hi

I just bought this 4 wheel drive Iron-Man-2 robot. Previously, I had only built two wheel drive robots and I’m struggling to get this thing moving on the ground as the motors seems to lack torque.

Currently, I’m power just the back 2 wheels via a Hbridge L298N motor controller supplied with 12V. I just wanted to test it before I powered the front wheels and I thought it would be enough to get it moving. Each motor is rated 6V. While the two back wheel spins pretty fast off the ground, it just stops once I place it on the floor.

If I was to power the front wheels using the same configuration would this be enough to get thing moving?

Can anyone recommend a 4 channel motor controller and a suitable battery (preferably a rechargeable one) I can use to get things moving? Configurations on 4 wheel drive robots seems to be scarce on the net.

I wonder what they used in the video on the site below:

(https://www.robotshop.com/en/iron-man-2-4wd-chassis-arduino.html)

Any help is appreciated.

Thanks

Vidura

2

Hello @Vidura and welcome to the forum,

The Iron Man-2 4WD Chassis uses 4 metal gear motors with the following specs:

  • Recommended voltage: 6-9 V
  • Stall current at 6V: 4 A per motor
  • No-load current at 6 V: 300 mA per motor
  • No-load output shaft speed at 6 V: 220 RPM

In order to choose a motor controller you have to consider the nominal voltage and the continuous current. As the specs of the motors used in the Iron-Man2 robot don’t mention continuous operating current, a simple rule of thumb is to estimate it at about 25% of the stall current, so let’s say it’s 1A.

The L298N motor driver allows controling two DC motors with voltages between 5 and 35V, with peak current up to 2A. However, if the motors stall, those 2A won’t be enough.

In summary, you will need a controller that can work between 6-9V and can provide 1A continuously and if possible 4A (or more) peak in case the motors stall.

If you want to run the 4 motors independently you could either use a 4-channel motor controller, like these:


Or use two dual motor drivers that work in that voltage range and can provide 1A continuously and 4A peak.

If you don’t mind running each motor independently you could connect two motors in parallel and use a dual motor driver that can provide 2A continuously (and if possible 8A peak).

There are many motor drivers available in the store, you can find them in the Brushed DC Motor Controllers section.

Let us know if you have further questions!

3

Hi Geraldine

Thanks for your detailed email.

You are right the motor controller isn’t sufficient for the job and its also dropping the voltage a lot. I also realised I need a better battery.

I bought a 2S 30C 7.2V Lipo battery with 4000mah. That should be enough going by 1A?

Thanks for the recommendations I will have a look at those controllers on the UK site.

4

Hi again,

Yes, that should be enough for running 4 motors consuming 1A continuously for 1 hour.

If you need further help selecting batteries I recommend checking this tutorial:

I’m glad I could help!

5

Hi Geraldine

Thanks for your help. Here is my final robot with facial recognition and text-speech.

1 Like
6

Hello again,

Wow, your robot is awesome! Thanks for sharing the video, it would also be great if you share your robot in the Robots Section that way you could participate in the Robot of the Month Contest.

Keep up the good work!

1 Like
7

Hi

Thanks, I will definitely enter it in to the competition.

you too :slight_smile: