Project 1: Basic Circuit & Sensor Reading Lab

This lab expands on basic circuit concepts by routing a multi-segment configuration on a single breadboard block. Section A features a series circuit where current passes through a 220Ω resistor and a 470Ω resistor sequentially, dividing voltage drop. Section B hosts a parallel junction dividing current across two identical 1kΩ resistors. Section C demonstrates a switch-activated 10kΩ pull-down resistor configuration, which forms the hardware foundation for digital button inputs in microcontroller projects.

Construct each circuit segment independently on your breadboard, and execute the voltage and current measurements at the specified target zones.

STEP 1

Assemble the Series Circuit (Section A)

Wire two different resistors sequentially to observe how voltage divides across series resistances.

Wiring Steps: 1. Turn OFF the main power source. 2. Insert a red jumper wire from the positive red power rail to Column 5, Row A. 3. Insert one lead of a 220Ω resistor (Red, Red, Brown, Gold) into Column 5, Row B. 4. Insert the other lead of the 220Ω resistor into Column 10, Row B. 5. Insert one lead of a 470Ω resistor (Yellow, Violet, Brown, Gold) into Column 10, Row C. 6. Insert the other lead of the 470Ω resistor into Column 15, Row C. 7. Insert a black jumper wire from Column 15, Row D, to the negative blue ground rail.

We place the resistors in series to establish a single electrical loop, forcing the exact same current to flow through both resistors while dividing the total voltage across them.

STEP 2

Measure Voltage Drops in the Series Circuit

Use your multimeter in DC Voltage mode to measure the voltage drops across each resistor and confirm the voltage addition rule.

Measurement Actions: 1. Turn ON the power supply. 2. Turn the multimeter dial to DC Voltage (20V range). 3. Place the red probe on Column 5 and the black probe on Column 10. Record V_R1 (Voltage drop of 220Ω resistor). 4. Place the red probe on Column 10 and the black probe on Column 15. Record V_R2 (Voltage drop of 470Ω resistor). 5. Place the red probe on Column 5 and the black probe on Column 15. Record V_Total_Series (Total voltage across both resistors). 6. Verify that V_R1 + V_R2 matches V_Total_Series within a tiny measurement error.

We measure voltage drops across individual series resistors to verify that the sum of local voltages equals the total supply voltage, matching Kirchhoff's Voltage Law.

STEP 3

Assemble the Parallel Circuit (Section B)

Wire two identical resistors in parallel to observe how current divides while voltage remains constant across parallel paths.

Wiring Steps: 1. Turn OFF the main power source. 2. Insert a red jumper wire from the positive red power rail to Column 25, Row A. 3. Insert one lead of the first 1kΩ resistor (Brown, Black, Red, Gold) into Column 25, Row B. 4. Insert the other lead of this resistor into Column 30, Row B. 5. Insert one lead of the second 1kΩ resistor into Column 25, Row C. 6. Insert the other lead of this second resistor into Column 30, Row C. 7. Insert a black jumper wire from Column 30, Row D, to the negative blue ground rail.

We align the two identical resistors side-by-side between columns 25 and 30 to expose both resistors to the exact same supply voltage, splitting the current evenly between them.

STEP 4

Measure Voltage in the Parallel Circuit

Measure the voltage drop across both parallel resistors to verify they are identical to each other and to the input voltage.

Measurement Actions: 1. Turn ON the power supply. 2. Keep the multimeter dial in the DC Voltage (20V range) position. 3. Place the red probe on Column 25 and the black probe on Column 30. 4. Note the voltage drop. It should equal the voltage of your power source (approximately 5V). 5. Touch the probes directly to the leads of the first resistor, and then the second. Note that both read exactly the same voltage.

We check parallel voltages to confirm that all branches connected directly to the same node share an identical electrical potential, which is a key trait of parallel distribution networks.

STEP 5

Assemble the Digital Input Pull-Down Switch Circuit (Section C)

Build a mechanical switch circuit with a pull-down resistor to produce clean high/low digital states for microcontroller inputs.

Wiring Steps: 1. Turn OFF the main power source. 2. Locate a 4-pin tactile push-button switch. Note that the pins are internally connected in pairs. 3. Insert the switch into the middle of the breadboard so its pins span across the center trench (e.g., pins on columns 40 and 42). 4. Connect a RED jumper wire from the positive red power rail to Column 40, Row A. 5. Connect one lead of a 10kΩ resistor (Brown, Black, Orange, Gold) to Column 42, Row B. 6. Connect the other lead of the 10kΩ resistor to the negative blue ground rail. 7. Connect a signal output jumper wire (e.g. green) to Column 42, Row C (this is the signal output node).

We install a pull-down resistor to tie the signal column to ground (0V) when the switch is open, preventing a floating high-impedance state that causes erratic digital readings.

STEP 6

Measure Pull-Down Input States (High vs. Low)

Use your multimeter to measure the signal output voltage when the push button is released vs. when it is held down.

Measurement Actions: 1. Turn ON the power supply. 2. Set the multimeter to DC Voltage (20V range). 3. Connect the black probe to the negative ground rail and keep it there. 4. Place the red probe tip on Column 42, Row C (the signal output wire). 5. Observe the voltage while the button is released. The meter should display 0.0V (logic LOW). 6. Press and hold down the push-button switch. Observe the voltage reading. The meter should jump to 5.0V (logic HIGH). 7. Release the button and watch the voltage drop back down to 0V immediately.

We measure the signal node to confirm that closing the switch overrides the pull-down resistor's weak ground connection, pulling the node to 5V and creating a clear digital toggle.

To verify that our physical circuits are wired correctly and matching theoretical engineering values, we process the measurements through a calculation pipeline. This verifies resistance sums, parallel branch splits, and pull-down logic thresholds.

Fill out the following structured Markdown log to record your calculated values against measured readings, checking that they fall within the 5% resistor tolerance limit.

Created Artifacts

Completed series-parallel analysis log table.
Detailed calculations showing percentage errors between measured and calculated currents.

Verification Proof

Close-up photograph of your breadboard showing all three completed segments (Series, Parallel, Pull-down switch).
A photo showing the digital multimeter probes touching Column 42 while pressing the switch, displaying 5V (HIGH).

Architectural Intent & Operational Impact

Why We Did This

Series circuits act as basic voltage dividers, which are essential when dropping higher voltages (e.g. 5V logic) to match lower voltage specifications (e.g. 3.3V ESP32 analog pins).
Parallel circuits allow independent branch currents, mirroring how multiple sensors are wired in parallel across shared power lines.
Pull-down resistors hold input pins at a known voltage (0V), ensuring digital registers don't bounce between states due to static noise.

What This Accomplishes

Demonstrates physical voltage and current distribution, ensuring you can calculate load capacities before attaching active loads like motors or displays.
Prevents floating-pin errors during sensor reading, preparing you to write clean button-interrupt code in NodeMCU and ESP32 programming.
Develops professional hardware testing methodologies, ensuring hardware configurations are proven correct before writing firmware.