Skip to content

Bench NotesUno handbook

ATmega328P · 5 V · 16 MHz

Bench Notes

Wiring tables, original diagrams and tested sketches for the Arduino Uno, written for the workbench. Find what you need by part, by topic or by searching.

35articles30sketches7topics

Start here

New to the Uno? Read these in order.

Step 1Uno Pin Map and Electrical LimitsEvery header pin on the Uno R3, what it can do, and the current limits that keep the board alive.
Step 2Your First Sketch: BlinkUpload a sketch that blinks the on-board LED and learn what setup() and loop() do.
Step 3How a Breadboard Is ConnectedWhich holes are joined inside a solderless breadboard, and the wiring mistakes that come from guessing.
Step 4Lighting an External LEDWire an LED with a resistor, get its polarity right, and blink it from a digital pin.
Step 5Fixing Upload ErrorsWork through the usual causes when the IDE cannot upload: port, board, cable, drivers and pins 0/1.

Topics

Every article belongs to one topic.

Getting Started

Pins, power, breadboards, LEDs and resistors: the groundwork every project needs.

Uno Pin Map and Electrical Limits, Your First Sketch, How a Breadboard Is Connected…

Workshop Projects

Eight complete projects built around pins wired straight into the Uno's header.

Variable-Duty LED Blinking, Analog Five-Position Servo Control, Seven-Segment Character Display…

Inputs & Sensors

Buttons, knobs and sensors for distance, temperature and light.

Reading a Pushbutton, Pull-ups and Debouncing, Potentiometers and ADC Readings…

Outputs & Displays

PWM dimming, seven-segment displays, shift registers and sound.

PWM, Seven-Segment Displays, More Outputs with a 74HC595 Shift Register…

Motors & Motion

Servos, servo power and DC motors through a driver chip.

Servo Basics, Powering Servos Safely, Driving a DC Motor with an L293D…

Programming Patterns

Serial, millis() timing, arrays, loops, interrupts and I²C.

Talking to the Serial Monitor, Non-Blocking Timing with millis(), Arrays for Pins and Patterns…

Troubleshooting

Upload failures and a method for finding faults.

Debugging Arduino Sketches, Fixing Upload Errors…

All articles

Search and filter the full list.

Search

Difficulty

AllBeginnerIntermediateAdvanced

Component

Topic

Uno Pin Map and Electrical LimitsEvery header pin on the Uno R3, what it can do, and the current limits that keep the board alive.

Your First Sketch: BlinkUpload a sketch that blinks the on-board LED and learn what setup() and loop() do.

How a Breadboard Is ConnectedWhich holes are joined inside a solderless breadboard, and the wiring mistakes that come from guessing.

Lighting an External LEDWire an LED with a resistor, get its polarity right, and blink it from a digital pin.

Choosing a Current-Limiting ResistorCalculate the resistor an LED or display segment needs, with a calculator and worked examples.

Using Analog Pins as Digital OutputsWhy A0–A5 can supply power to a potentiometer, as the workshop projects do, and where the trick stops working.

Variable-Duty LED BlinkingA potentiometer sets how much of each one-second cycle an LED stays on, from 20% to 80%.

Analog Five-Position Servo ControlA potentiometer snaps a servo between five fixed angles: 0°, 45°, 90°, 135° and 180°.

Seven-Segment Character Display: LUCESpell L-U-C-E on one common-cathode seven-segment digit using pins 2–9.

Servo Stepping with a PushbuttonEach button press turns a servo 45° further, wrapping from 180° back to 0°.

Five-Speed Symmetrical LED BlinkingA potentiometer picks one of five blink speeds; on and off times are always equal.

Custom Servo Angle SequenceA button steps a servo through a list of angles stored in an array: 90, 45, 135, 0, 180.

Seven-Segment Character Display: LAOSSpell L-A-O-S on a common-cathode seven-segment digit with the same pins as LUCE.

Three-Zone Potentiometer Servo IndicatorA servo rests at 90° and repeatedly waves toward 45° or 135° depending on which third of the knob is selected.

Reading a PushbuttonRead a button with an external pull-down resistor and learn why an unconnected input floats.

Pull-ups and DebouncingUse INPUT_PULLUP for a one-wire button, then debounce it with millis() so each press counts once.

Potentiometers and ADC ReadingsTurn a knob into a number from 0 to 1023 and convert it to volts.

Measuring Distance with an HC-SR04Trigger an ultrasonic ping, time the echo with pulseIn(), and convert it to centimetres.

Reading Temperature with a TMP36Convert the TMP36's analog output to degrees Celsius, with averaging to steady the reading.

Sensing Light with a PhotoresistorBuild a voltage divider with an LDR and turn on an LED when it gets dark.

PWM: Dimming an LEDUse analogWrite() and a potentiometer to set LED brightness, and see what PWM really does.

Seven-Segment Displays: Common Anode vs Common CathodeIdentify your display's polarity and drive digits 0–9 with one switch for either type.

More Outputs with a 74HC595 Shift RegisterDrive eight LEDs from three Uno pins with a 74HC595 and shiftOut().

Playing Tones with a BuzzerPlay notes on a passive piezo buzzer with tone(), and know when you need an active buzzer instead.

Servo BasicsHow hobby servos are controlled, their wire colours, and a smooth sweep with the Servo library.

Powering Servos SafelyWhen a servo needs its own supply, how to wire it with a common ground, and how to spot power problems.

Driving a DC Motor with an L293DControl speed and direction of a small DC motor through an H-bridge driver, never straight from a pin.

Talking to the Serial MonitorPrint values, read typed commands, and avoid the baud-rate and line-ending traps.

Non-Blocking Timing with millis()Blink two LEDs at independent rates without delay(), using rollover-safe elapsed-time checks.

Arrays for Pins and PatternsStore pin numbers and timing in arrays to drive five LEDs with a few lines of code.

For Loops: Fades and RepeatsUse for loops to fade an LED in and out and to repeat a blink a set number of times.

Hardware InterruptsCatch button presses the instant they happen on pins 2 and 3, with safe ISR and shared-variable rules.

I²C Basics and a Bus ScannerWire an I²C module to A4/A5 and find its address with a scanner sketch before writing any driver code.

Debugging Arduino SketchesA repeatable process for finding faults: switchable debug prints, a heartbeat LED and checks with a meter.

Fixing Upload ErrorsWork through the usual causes when the IDE cannot upload: port, board, cable, drivers and pins 0/1.