PCB design glossary
ERC
AKA: electrical rule check
Electrical Rule Check — automated verification of a schematic for connectivity and pin-usage errors.
ERC scans a schematic for electrical problems: unconnected pins, two outputs driving the same net, a power pin with no source, conflicting pin types. It catches mistakes early — before they become layout headaches or bricked prototypes.
ERC runs on the schematic only. Its layout-side counterpart is DRC, the Design Rule Check.
What ERC checks
ERC works from pin types. Every pin on a schematic symbol is marked as an input, output, bidirectional, power input, power output, passive, open collector or no-connect. ERC then checks the combinations on each net:
- Two outputs driving the same net.
- A power input with nothing supplying it.
- Unconnected pins that are not marked no-connect.
- A net with only one pin on it.
- Conflicts such as an output tied straight to a power pin.
The power flag
A classic ERC error is 'power input not driven' on a rail that comes from a connector or a battery. The connector's pins are passive, so ERC cannot see that they supply power. KiCad solves this with a PWR_FLAG symbol placed on the net, which tells ERC the rail is driven from outside.
What ERC cannot catch
- A symbol whose pin numbers do not match the real part.
- Wrong component values, or the wrong part altogether.
- A circuit that is connected correctly but designed wrong.
- Anything physical: clearances, footprints and trace widths belong to DRC.
Catch the floating pin while it is still a schematic
Every design built in PCBEditor gets an electrical check, and each finding is explained in plain words: what is wrong, why it matters, what to change.
Start from a schematic