OBSERVE. TRACE. REPAIR.
Circuit Detective
The LED stays dark. Follow the clues, inspect the connections, and make a repair that brings it back to life.
0 of 5 mysteries repaired this session
Choosing a mystery loads its original wiring. Your repaired count stays until you leave or start a fresh session.
MYSTERY 01
The stubborn LED
5 V DC supply: + at LP1, − at LN1.
R1 = 1 kΩ · LED forward voltage ≈2 V.
Make a repair
Select a part and lead. Click a board hole or choose its name, then move the lead. Power stays off while editing.
Choose a part to inspect its endpoints.
Inspect the connections, then try a repair.
One way to repair it
Click a hole to inspect its internal group. On small screens, scroll sideways to see all columns.
Highlight = internal stripBlue ring = selected partFilled dot = inserted lead
Select a hole to trace its connections.
Trace each component
LED first lead = anode (+). LED second lead = cathode (−). Select a part below to edit it.
Why your repair works
The nominal current is (5 V − 2 V) ÷ 1 kΩ = 3 mA.
FIVE MYSTERIES REPAIRED
You followed the connections.
You checked polarity, traced the return path, distinguished rows, and spotted a split rail. These are useful habits for your next real circuit.
Revisit the breadboard lesson →BUILD A TROUBLESHOOTING HABIT
Follow one complete path.
Start at the positive supply terminal. Follow the feed wire, resistor, LED anode, LED cathode, and return wire to the negative terminal. A connection must share an internal strip or a wire; being close together does not connect two holes.
Change one thing, then test.
Use the component list to read exact hole names. Click holes to see the internal groups. If a repair fails, compare the two nodes at each component, undo your idea by resetting the mystery, and try again.
The + and − rail labels do not supply power by themselves. In these mysteries the virtual supply is attached specifically at LP1 and LN1. A dashed line marks a rail break between rows 6 and 7.
This is a guided DC connection model with a fixed 5 V source, 1 kΩ resistor, and nominal 2 V LED. It checks connectivity and orientation; it does not model reverse breakdown, component damage, or real LED brightness. Disconnect a real circuit before rewiring and check component datasheets.