Connect Floating GND to Chassis GND

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TXRX

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Hi,

See attached, I have uC that has pulse output of +3.3V connect to pulse convert circuit - both of them have GND that relate to chassis, the pulse voltage at the output of the pulse converter is 28V relate to GND chassis.

I want to provide the pulse to unit A which has Floating GND, i can not to connect the floating GND to the chassis GND, how can i connect the floating GND to the Chassis GND ?

Thanks,

Doron
 

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If you want to connect a floating ground to a physical ground, please use a small resistor. The real value may depend on the circuit, power and voltage levels. Avoid capacitors.
 

The easiest way is using optocouplers (see the attach).
And if you unit A needs strictly 28 V pulses, then it must have it's own isoltated 28 V supply rail.
But be aware of possible high-voltage between different grounds, you might need to place a resistor between grounds.
 

c_mitra said:
If you want to connect a floating ground to a physical ground, please use a small resistor. The real value may depend on the circuit, power and voltage levels. Avoid capacitors.
Click to expand...

I did not mention at the drawing but at unit A there a resistor of 3K between Floating GND to Chassis GND, i do not want to reduce the resistance with a another resistor so i search for other solutions ?
 

It is never a good idea to keep grounds floating; the actual potentials on different parts becomes meaningless.


In the sketch you made, the pulse will be not supplying much current load and 3K connection between the floating and real ground is ok.
 

use an opto coupler or Pulse transformer or Opto isolator
 


At unit A there is resistor ok 3K between Floating GND to Chassis GND.
 

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