~60 min. Build the simplest active circuit on a breadboard: 9V battery + 470Ω resistor + LED. Master breadboard discipline before any complexity arrives.
Goal: build your first breadboard circuit; develop color discipline and wire-management habits
Estimated time: 60 minutes (deliberately slow; the speed is not the point)
Prerequisites: lab 1.1 + lab 2.1 complete; kit unboxed
Steps
Step 1: Identify breadboard regions (5 min)
Look at your breadboard. Top rails: two horizontal strips (typically marked + and -). Bottom rails: the same. Middle: two columns of vertical tie-strips, with a gap between them. Mark which is the power rail and which is the ground rail (the breadboard's printed + and - lines indicate the convention)
Step 2: Power the rails (10 min)
Plug the 9V battery's + lead (red) into the top + rail (red). Plug the - lead (black) into the top - rail (black). Use a short jumper to bridge the top + rail to the bottom + rail (so you have power on both sides; useful when wiring gets dense). Same for ground
Verify with the multimeter: probe top + rail to top - rail; should read ~9 V. Probe bottom + rail to bottom - rail; same. Probe top + to bottom + (no voltage; same rail)
Step 3: Build the LED circuit (15 min)
From the + rail: insert one end of a 470 Ω resistor into the rail; insert the other end into a tie-strip in the column. Two rows down: insert the LED's anode (long lead) into the same tie-strip; insert the LED's cathode (short lead) into a different tie-strip. From that tie-strip: jumper to the - rail
The LED lights. If not:
- Check LED polarity (anode = long lead; flat side of LED body = cathode)
- Check the resistor isn't broken (measure with multimeter; should be ~470 Ω)
- Check the battery is fresh (measure across the rails)
Step 4: Practice rewiring (15 min)
Disconnect everything except the rails. Rebuild the same circuit using a different column of tie-strips. Same result: LED lights. The breadboard's columns are interchangeable
Now: build the same circuit with the LED reversed (anode to - rail, cathode toward +). LED does not light. Confirm the LED's polarity matters
Step 5: Multi-LED circuit (10 min)
Add a second LED + resistor in parallel with the first (both share the same + and - rails through separate resistors). Both light. This is the parallel pattern
Try in series: + rail → resistor → LED → LED → ground. Probably both light dimly (the 9 V supply is now driving two ~2 V drops plus the resistor; the math works but each LED gets less current than before)
Step 6: Document and clean up (5 min)
Photograph your finished circuit. In your lab notebook: note the resistor values, observed LED brightness for each variant, anything unusual. Disconnect the battery before walking away (a connected battery slowly drains)
Expected output
- Working LED circuit on a breadboard
- Photo of the circuit
- Notebook entry comparing parallel vs series LED configurations
Common pitfalls
- Power and ground rails not extended to both sides: many breadboards have a break in the middle of each rail. If your circuit on the bottom half of the board doesn't get power, that is why. Jumper across the break
- Loose wires: jumper leads with bent or trimmed-too-short ends slip out. Use straight, full-length jumpers when possible
- Tie-strip confusion: the tie-strips run vertically (down the column) in groups of 5; they don't run horizontally across the central gap. Putting two parts on either side of the gap means they're not connected
Stretch (optional)
- Build a three-LED display: red, yellow, green in a vertical line. Make a small "traffic light"
- Use jumper wires to wire the LED 6 inches away from the power rail (long-jumper practice). Notice how the circuit's behavior is identical; the wires are just transport
- Build the same circuit on a piece of paper as a schematic (no breadboard). Compare your hand-drawn schematic to what is on the breadboard
Lab 3.1 v0.1. Foundational. Breadboard discipline starts now.