I have a vintage 0-30A DC ammeter (picture below) and I want it to display my PC's CPU usage for a DIY project. After doing a bunch of research, here's how I would do it:
The PC will send CPU usage data to an Arduino, which will then regulate the voltage (through pulse width modulation PWM) based on the CPU usage data. My understanding is that the Arduino can regulate voltage between 0-5 V, and I will write a program to determine the right amount of voltage to swing the needle to where I need it on the ammeter. So I need to find a way to swing the needle to 30 A on the ammeter (which reflects 100% CPU utilisation) with 5 V power.
With my very limited knowledge in electronics, I guess I need to use the good ol' Ohm's law here:
resistance = voltage/current = 5 V/30 A = 167 mΩ
My question is: Do I just put a 167 mΩ resistor in series with the ammeter and Arduino and it'll generate a 30 A current to move the needle on the ammeter to the maximum? And a 30 A current sounds high. Does that mean I'll have to use wires with the right "thickness"?