I am working on a bipolar power supply for hobby and educational purposes. Concerning the schematic, is it possible/good practice to place devices that don't go on the PCB in the schematic?

Specifically, I have chassis mounted connectors, TRS and XLR, along with a chassis mounted transformer. Should/Can these be shown on the schematic without generating nets for their connections? The transformer primary, power inlet connector, and fuse are all point-to-point wired, with only the transformer secondary entering the PCB. Should these point to point connections be shown?

If its of any importance, I'm using Proteus 8.

  • \$\begingroup\$ The question "Is it possible to have a component on the schematic but exclude it from the netlist?" is a good one. The answer would depend on whether or not the EDA package supports that. BTW, we had a similar question recently. \$\endgroup\$ Sep 8, 2014 at 23:19
  • \$\begingroup\$ You're using TRS and XLR for power connections? Sounds to me like a good way to blow up some pro audio gear. Circuit issues aside, please consider some connectors that are not typically used for signals. \$\endgroup\$
    – AaronD
    Nov 5, 2015 at 20:05

3 Answers 3


I am not a professional PCB designer.

My rule is: put all the connected electronics on the schematic.

The chassis-mounted parts need nets for their connections, otherwise what will they connect to? The simplest way to achieve this is put the chassis-mounted parts on the schematic.

The chassis-mount parts will need a PCB footprint for the connecting wires. So I design that footprint (set of holes) for the PCB, and it is self-consistent; the PCB is constrained to support the schematic.

Further, the PCB footprint can have a silkscreen label, showing how to wire it to the chassis-mount parts.

Also, I can generate an assembly guide from similar information.

I can derive the Bill-of-Material from the schematic, and I have less chance of forgetting something. I don't need to look in two places to know what the circuit will be.


Normally, you put something on the PCB to connect to these components. Vias, pads, a connector, something. That something should be present on your schematics, since you'll have to use some footprint object in the PCB editor, and the component used in the schematics editor should correspond to the footprint object in the PCB editor.

  • 2
    \$\begingroup\$ Just to emphasize this - the PCB footprint specified on the schematic for an off-board component need not bear any relation to the real component, other than having the right number of pins. \$\endgroup\$ Sep 9, 2014 at 0:24
  • \$\begingroup\$ Also, put the off-PCB components onto a separate sheet of the schematic. \$\endgroup\$
    – user32885
    Sep 9, 2014 at 8:03
  • \$\begingroup\$ Often the area with off board components is marked / segregated with dotted lines "--- --- ---" These are not wires but "Drawn" features \$\endgroup\$
    – Spoon
    Sep 9, 2014 at 8:06

In our project, for every box we maintain two sets of schematics -- 1) electronics, 2) electrical.

As the name suggests, electronics folder contains schematics and pcb file, along with generated BOM and gerber files.

Electrical folder contains everything else that do not go into the PCB. For example, power socket, transformer, wall-mount connector, LCD, and their wiring diagram. Naturally BOM for electrical components are generated separately.

During production, the empty boxes are wired and PCBs are soldered on two parallel work benches using their respective BOM. Then they are sent for assembly and testing.


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