Set ground & supply

Before circsim can solve a circuit it needs to know two things: which net is ground (the reference every voltage is measured against) and where power comes in. Both are handled in the Ground & Power panel in the right dock, though Energize will make reasonable choices for you automatically.

Designate ground

Ground becomes SPICE node 0: the reference for the whole simulation. A circuit with no ground can't be solved, so Power On and Run show a "Designate a ground net first" card until ground is set (Energize sets it for you when it can recognise a ground name; on a board with only auto-generated net names such as Net-(R1-Pad1) it shows the same card and waits for you to pick the net).

circsim suggests a ground net from the net names (GND, AGND, VSS, 0V, …). To confirm or change it:

• click a suggested net chip in the Ground & Power panel, or
• click the actual net on the 3D board.

Once set, the panel shows the ground net in green. Use Change… to pick a different one; the quick-pick chips beside it are ranked, with ground-named nets (AGND, PGND, VSS, …) first and then the nets with the most pads.

Wrong ground = wrong everything

If your voltages look bizarre (or the solve won't converge), the ground net is the first thing to check. Every voltage is relative to ground: pick the wrong net and the whole picture shifts.

Attach a supply

Power enters the simulation through a bench instrument, not through the board's connector (a bare-board connector is electrically open; there's no battery on it). The Ground & Power panel makes this one click:

• Suggested supply nets appear as chips (best candidate first). Click one to clip a 5 V, 0.1 Ω DC supply onto that net. A net that's already supplied shows a ✓. Click it to edit the supply instead of stacking a second one.
• If your rail isn't suggested (an unusual name), click Choose…. The list is ranked the same way the suggestions are (likely power names first, then the nets with the most pads) and has a filter box, so on a board with hundreds of nets you can type part of the name. It shows the top 50 matches at a time.

The supply shows up as a Power supply (PSU) front panel on the bench shelf, where you can adjust its voltage, series resistance, or re-route its lead.

Or just Energize

If you don't want to think about any of this yet, press ⚡ Energize. It designates a ground net, clips a 5 V supply onto the best-looking power net if you haven't attached a source, and solves, all in one click. Once you're driving the bench deliberately, use Power On, which never rigs anything and leaves ground and supplies entirely to you.

Next

• Energize & read the operating point
• Use the bench & draw leads: attach more than one supply, or a function generator.