I have a brushed DC motor measures at 2.8A when it first starts for a few seconds then drop to 1.7A at normal speed. I wonder if I connect it with the L298N motor shield, would it burn the shield ? I understand the motor shield can handle a maximum of 2A.
if the shield has a large heat sink it should be no problem as the L298 has 2 outputs that can be used together to get 4A.
If there is only a small or no heat sink at all there is still the L298s internal overheat protection which will prevent if from failing immediately - however you won't be able to get full power and the chip may be killed after some time. (I found the L298 to be quite sensitive to constant overtemperature - despite its protection circuit)
The shield has a large heat sink so I think it may be ok. There are 2 outputs on the board. I plan to use the motor for low speed so I think it may be ok. I concern only when the motor first starts, it draws higher ampere than the board specified but last only a few seconds. I will give it a go.
Thanks for your help.
Using both channels in parallel should be OK. However, you'd be better off using a mosfet h-bridge chip such as Pololu - MC33926 Motor Driver Carrier. It has a much lower voltage drop than the L298N, so it runs much cooler and needs little if any heatsinking.
If you do use the L298N, then you need to provide a supply voltage around 3V to 4V higher than the motor voltage, to allow for the voltage drop in the device.