I'm designing a digital I/O, and for the outputs I have ULN2803 and relays. I have the schematic below.
The coil current of relay is 16.7mA, ULN2803's max input current is 1.35mA and output current is 500mA/per channel used.
How should I calculate the current limiter resistors? My MCU works with 3.3V, driving the relays with 24V. What happens if a current flows more than 16.7mA to the relays?
And should I use pull-up or down resistors for input and outputs. I don't want any floating pin and activate the relay when I don't want.