I'm currently working on a project of a heavy weight car (around 11-12 Kg) and I want to control 4 DC motors to run this car using an Adafruit L293D motor shield.
Each motor is 12V, I have connected a 12V DC supply to one motor and measured the current drawn from it and it was 223 mA, I grabbed the shaft very hard (as a heavy load) until I felt heat and the current reached 500mA, if I multiply it by 4 for all motors it's 2A, which will result in an overheat as written in the shield data sheet. I'm not sure if the current will be higher than 500mA.
Right now I'm thinking about a mechanism to protect my shield from overheating before connecting the circuit with the car.
I was suggested to use a very big heat sink for protection, the guy who suggested that said it will work with me because it worked with his 7 Kg car, even though the sink got very hot, but the car worked well.
Another solution I though about but not sure if it will work, is to connect 4 12V relays out of the + - ports of the shield to the motors (a relay between the shield and a motor), will this work? Or is it actually possible?
If it is possible, can I use analog pins as digital pins trick to control the relays? Because I used all of the digital pins for this project.
Currently I ran out of time because I spent a long time on the mechanical aspect of the project, and I don't think I'll have time to change the shield, and at the same time I'm afraid to test the circuit on the car....... I will appreciate any advise from you to protect my circuit from over heating