Hi everyone! first post here..
I need help with my arduino project. I have several machines that I want monitor. Each has a relay that is powered when machine has failure. These relays are connected to arduino with approx 100 meter long wires:
Currently I have 100 ohm pull up resistors in each digital pin and a software that checks the digital pin state every 2 seconds. If it's LOW then it writes "Alarm in device X" to serial.
The problem is that the industrial environment where the machines are is very noisy. These 100 meter long wires run next to big cables with large currents. So every now and then arduino senses the pin LOW even if the machine doesen't have failure.
I was thinking to put second relay next to each digital pin to trigger the pin and then control the coil (12 volts) with this relay in machine. Now I would have short wires to digital pins that don't act as antennas.
Is there a more efficient way to achieve reliable sensing of digital pins?? I think adding 100pF caps between the digital pin and ground isn't enough to filter the noise. If I disconnect these long wires from arduino and connect a led to them, the led blinks randomly, so the noise is quite strong..
Thanks for your help!