L293D shutting down my laptop.

Other Hardware Motors, Mechanics, Power and CNC
1

Hello all,

I've just started working with electronics and Arduino. I'm trying to get my robot working without buying a motor shield (off of parts from my kit) but I'm running into lots of problems.

I have a single L293D chip which I am using to power the motors. They are 6V motors with a stall current of 1.8A (yes I know the L293D only supports 600ma per channel). I was hoping to run both motors at low power (say 20%) since it doesn't need to move very fast. Right now the robot is elevated so there is very little load on the motors while I am testing.

My power supply for the motors is 12V, and when I tested a single motor at full power it seemed to work fine at 12V. I ran it for several minutes and the chip barely got warm. The other side of the chip is connected to 5V from the Arduino and nothing else. All the grounds are connected.

I tested both motors independently with this setup and it worked fine. However, as soon as I try to hook up both motors simultaneously, my laptop SHUTS DOWN when I connect the motor power supply. What is going on here? I don't even know how to troubleshoot this. I don't want to try connecting it again in case I destroy my laptop.

Any ideas on what is going on here or how to proceed?

Thanks,

Austin

2

It is possible that the L293D is failing catastrophically and somehow injecting noise into the USB supply, or encouraging too much current draw from the USB port.

The L293D is totally unsuitable for your project.

If you want it to work, buy a modern motor driver with the required current handling capability, like this one.

3

jremington:
It is possible that the L293D is failing catastrophically

And the next thing that will fail catastrophically is the laptop.

...R

4

What may be happening is two motors overpower your 12V supply, dropping it down to below 5V, at which
point the internal circuitry in the L293D routes current from its logic supply to the motor, overloading the
USB controller in your laptop.

I'd recommend a powered USB hub if you want to isolate your laptop from misbehaving USB loads, or
use a power bank when testing with 12V attached (ie no laptop connection at all).

Note that two 6V motors with 1.8A stall current at 6V will together try to pull around 7A from a 12V
supply.