Meanwell Power Supply AC Ground and V- Connection
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@SupraGuy as the 3.3 rail is easily damaged by shorts would it make sense to select the diodes to avoid conduction below say 6V?
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@doctrucker If anything, the opposite. The conducting voltage of the diodes is the maximum differential from earth that the circuit ground can be without conducting through the resistor. This is ONLY to avoid ground loops, not as any kind of circuit protection. Nothing that you do here is going to prevent damage to the 3.3V rail if it allows that rail to work at all.
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@supraguy Thanks again. I now better appreciate the main purpose of this is to reduce ground loops and can see the resistor normally conducts, the diodes are just high current paths in the event a significant voltage gets shorted to earth.
As I understand it in the event of a short to metal work of DC voltages in the system these diodes will conduct if their threshold voltage is exceeded. Would it be possible to monitor for current flow through D1 and D2 (sense resistor in series?) and use that to break an interlock loop if detected?
For example a VIN short on the posative side of a heater should blow a DC circuit fuse. Short on the negative side is indestinguishable from normal opperation from the PSU perspective but should cause a voltage across a sense resistor in series with D1/D2.
My dual interlock loops currently combine at the PS_ON pin on the duet. It would be my intention to add this just before that - ground negative on one side and drain from relays (with flyback/freewheel diodes) on the other.
The objective is to detect the serious wiring anomaly (which maybe causing a heater to heat unexpectedly) and stop the system.
