Elihu
Industrial
- Apr 22, 2008
- 5
When building small control panels w/PLC's I'm usually adding them to an existing control for a large machine. The OEM control is often an all AC relay-based system, with a 24VAC control voltage, and 240 (or 480) 3-phase powering the big motors, etc.
I mount a 24VDC supply to run my PLC, sensors, etc, and I "talk" to the OEM control through relay outputs.
I usually just float the DC negative, and everything works fine. But I think I should be tying the DC negative to the machine ground. Should I be doing this every time? Is there a down-side to tying my DC negative to ground?
Yes, the (Automation Direct) PLC's input power plug has a ground terminal (which I use) -- but this doesn't tie the negative to ground.
I mount a 24VDC supply to run my PLC, sensors, etc, and I "talk" to the OEM control through relay outputs.
I usually just float the DC negative, and everything works fine. But I think I should be tying the DC negative to the machine ground. Should I be doing this every time? Is there a down-side to tying my DC negative to ground?
Yes, the (Automation Direct) PLC's input power plug has a ground terminal (which I use) -- but this doesn't tie the negative to ground.
