I'm using a motor shield with h-bridges rated for 1.2A, 3A peak (specifically the Adafruit Motor Shield v2). After some troubleshooting when the motors on terminals M1 and M2 wouldn't run, I touched the chip and it took about ten minutes for my finger to stop stinging. The motors work fine on other terminals, and other motors do not work on M1 and M2. Since I found no other problems in the code, I'm assuming I broke it.
The motors that were running on M1 and M2 are two, 12V DC, no-load 0.23A and stall current 3.6A.
I'm prepared to buy a new shield and put on heat sinks, but obviously want to keep the same thing from happening again. Can I still use the same shield if I use heat sinks and am more careful to prevent the motors from stalling? Could I put fuses rated at 3A between the terminals and the motors to keep the motors from over-drawing? If not, are there any other solutions besides purchasing a rather pricey higher-amperage motor shield?
Can I still use the same shield if I use heat sinks and am more careful to prevent the motors from stalling?
Start-up current can be similar to stall current. And, it's generally a good-practice to leave some safety margin so I'd "feel better" if the motor drivers were rated at 4A or more.
Are the still-working drivers getting hot? If not, maybe the chip was defective or maybe there was some other problem?
A fuse might work, but usually a fuse is used to prevent a fire or further-damage after something has "gone wrong". There's an old joke, "The transistor blew, saving the fuse". But more often, the semiconductor shorts-out and then the fuse blows so you usually have to replace them both.
And of course, if the fuse blows your motor won't run so you've still got an unreliable system.
I touched the chip and it took about ten minutes for my finger to stop stinging.
Next time, wet your finger first. Sometimes I'll put a little drop of water on the chip to see how fast it evaporates, or if it boils right-away. I've used a little dispenser bottle, or a syringe, or the stick of a wooden Q-tip dipped in water.
DVDdoug:
Start-up current can be similar to stall current.
It is exactly the same if you use on-off control, since the motor is stationary at start up
with full voltage across it.
Ramping-up PWM at start will reduce startup current considerably, and is mechanically
smoother.
Next time, wet your finger first. Sometimes I'll put a little drop of water on the chip to see how fast it evaporates, or if it boils right-away. I've used a little dispenser bottle, or a syringe, or the stick of a wooden Q-tip dipped in water.