When I use the servo motor (from the original starter arduino kit) with the PIR sensor, it works well (in both way of powering from USB and external power supply).
However, when I changed the motor with a stronger one (MG995), it seems something wrong within it: the motor doesn’t spin much and the “L” LED light blinked constantly. So I guess probably the power input doesn’t supply the enough amount to supply this stronger motor. And when I switched the adapter to a higher voltage, the situation remained the same.
I tried to use the multimeter to measure if the adapter could supply a correct power.
And yes, it did.
Next, I tried to demonstrate if my circuit works well, so i connect the power into pins directly (using 5v external power supply machine).
And yes, the motor did a good job with PIR sensor!
In this case, I suspected the problem might be in the input port.
And probably right. No matter how much i tried to input(with 5-20V) through the port(circled in green), the real voltage runs through the circuit is only 4.3V. That’s why my motor couldn’t spin much.
Is it because the board have to protect itself within 5V to operate? But 4.3V is way too low, even lower than powered by USB. And in that case, how could it support to operate a stronger motor(normally 6V)?
FYI, here is a short video shown how it works in my expectation by powering directly in pins!