24vdc Positive grounding

Question

24vdc Positive grounding

JLBEngineer (Electrical)

(OP)

4 Apr 16 12:06

Is it acceptable in the US for a machine to have the positive terminal grounded on the 24vdc power supply?
The machine was developed in Japan.

Ran into a problem when connecting computer laptop to machine PLC seems to be a ground issue since the laptop
computer uses common (negative) on AC power supply (power plug has ground connection). Grounding issue was overcome by using a computer power supply with no ground on plug to the AC outlet.

IRstuff (Aerospace) · Answer 1 · 2016-04-04 13:02:32

I believe there are cars with positive grounds. You should use an optical isolation scheme on the communications line, rather than compromising safety.

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mcgyvr (Mechanical) · Answer 2 · 2016-04-04 14:16:48

If the "machine" requires -24VDC then sure..

Is the power supply part of the machine?
Does the instructions for the machine require an isolated supply?

itsmoked (Electrical) · Answer 3 · 2016-04-04 21:03:33

That is very weird even for a Japanese machine. I think something is wrong. You should contact the maker and ask about that.

Keith Cress
kcress - http://www.flaminsystems.com

ScottyUK (Electrical) · Answer 4 · 2016-04-05 05:06:04

A lot of older telephony systems used positive earthed supplies because it prevented corrosion of the metal conductors due to galvanic actvity between the metal and the mass of earth, rather than accelerating corrosion by actively driving the corrosion cell as would happen with a negative earthed system.

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