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enter image description hereI recently designed a capacitor discharge welder for my welding applications, and I come through a problem about separating grounds between AGND of the controller and (-) terminal of the big 1.3 farads 20 volts cap. after some hanging around on the web, several questions have been confusing me.

  1. placing a separation gap between grounds on PCB and connect them through a zero-ohm resistor.
  2. Connect the grounds as normal but in this situation, due to my lack of knowledge, in the discharging period, the capacitor might cause fluctuating the ground thus damaging the micro-controller.

Any help would be appreciated

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if you use a slot between two regions of ground, and a narrow connection pathway, you will have at least 12dB attenuation per square of metal in the connection. This is illustrated in the 3rd example below.

To make measurements using the ADC, you can use differential inputs to the ADC.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Won't that setup be pretty noisy due to return currents having to take the scenic route? Unless I'm misinterpreting your diagram and the intention is to run the signals over the ground bridge. I would think just separating the two sections a far enough on the ground plane far enough so that their currents don't flow under each other would be enough. \$\endgroup\$ – DKNguyen Jul 26 '19 at 15:47
  • \$\begingroup\$ The ADC measurement is differential. The control of the FlipFlop can be 5 volt into 10Kohm, and starts the pulse. The designer has to implement "local battery" rail filtering, to ensure the fast current surges are provided locally ---- to the MCU, and to the Welder. Some inductors in the rails, to implement low-pass-filters, is the key. \$\endgroup\$ – analogsystemsrf Jul 26 '19 at 15:52
  • \$\begingroup\$ currents on a plane will always intermix; use the slot if you want lots of attenuation (for precision measurement) of GND currents. Make a mud-pie, and push with your fingers on one region of the mud. The other locations in the mud will be upset, no matter where you push. Unless you use two separate pieces of mud. \$\endgroup\$ – analogsystemsrf Jul 26 '19 at 15:55

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