I am working on an Arduino based project, which required to supply 24VDC at 2A and 3 PWM outputs from the main board to the other board. The 24VDC is for powering the LEDs, and PWMs are for dimming control. To make wiring simpler, instead of running 5 separate wires (3 PWMs, 24VDC, and GND), I plan to use a multi-conductor cable like this and circular connectors like this
for this purpose.
Is this a proper way of delivering both power and signal through the same cable? What other methods are recommended?
Best Answer
I would suggest using separate wires for current return ("supply ground") and digital ground. Connect them at each end via small-value resistor. Suppose the wires in your cable are 0.5 ohms. If you didn't separate out your supply and digital ground, then you'd lose two volts (out of 24) in your cable. An 8% energy loss in the cable isn't wonderful, but it's not the worst thing in the world. On the other hand, the ground level at the power consumer would be a volt higher than at the supply, meaning that a logic 1 which was output as 3.3 volts would be seen at the other end as only 2.3
If the main power supply was connected to the digital logic with a 1 ohm resistor on the ground side, there would be two paths via which ground currents could flow--direct through the supply return (0.5 ohms), or else through two ohm resistors and the data ground (2.5 ohms). The downstream supply ground would be 0.83 volts above the source ground level, but the two digital grounds would be within 0.17 volts of each other (at the supply, digital ground would be 0.33 volts above supply ground; at the load, the digital ground would be 0.33 volts below supply ground).