Blink an LED
One second on, one second off, forever. Where everything starts.
led
Indicator
LED 0603 (indicator)
ledGPIO
Why this support circuit is added
Status LED.
Grounded in the catalog and golden patterns (real open-source circuits). Every auto-inserted part comes with a reason.
Support circuit added automatically1
Using this part in a project adds the circuit below, each element with its reason.
Series resistor
A → MCU
Without a series resistor both the LED and the MCU pin overcurrent.
InterfaceGPIO
- Catalog id
- led
- Category
- Indicator
- Protocol
- GPIO
- Logic level
- Unrestricted (uses the board rail)
Firmware detection0
No library reveals it — add it from the module checklist in your project.
Examples using this part
Run them in the browser, no login needed.
Fade an LED up and down
analogWrite walks D13's brightness up and back down forever.
led
Turn an LED on while a button is held
D13 lights only while the button is pressed.
buttonled
Use the built-in pull-up
Reads a button with INPUT_PULLUP and no external resistor — pressed reads 0.
buttonled
Debounce a button
A button bounces on contact; waiting 50 ms turns the noise into one press.
buttonled
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Count button presses
Detects the moment a button goes down, not whether it is down.
buttonled
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Blink without delay()
Times the blink instead of stopping — the shape you need to do two things at once.
led
A knob sets the blink rate
The A0 reading is used directly as the delay, so turning it speeds the blink up.
ledpot
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Fade with for-loops
Two for-loops walk the brightness up and back — the same result as Fade, written differently.
led
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Calibrate a sensor to its own range
Learns the lowest and highest values it sees in the first five seconds, then scales to those.
ledpot
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Draw a bar graph with ten LEDs
The higher the reading, the more LEDs light. The simplest way to see a number.
ledpot
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Light up past a threshold
The LED comes on only when the reading crosses a number you chose. if in its simplest form.
ledpot
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Light several in sequence
A for-loop runs along a row of LEDs and back. This is what loops are for.
led
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Keep going while a button is held
Stays inside the while-loop for as long as the button is down.
buttonledpot
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React to a letter you type
Sending a–e over serial lights the matching LED.
led
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Keep pin numbers in an array
Lists the LED pins once and walks the list, instead of naming each pin by hand.
led
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A pull-up button and an LED
D13 lights up while the button is held. Start here.
buttonled
Night light
The darker the light sensor reads, the brighter the LED — the brightness is an analogWrite duty cycle.
ldrled
Motion lamp
A PIR sensor lights the lamp and holds it on for three seconds after the last movement.
hc_sr501led
Parking sensor
An ultrasonic range finder beeps at shorter intervals as something gets closer, and lights an LED inside 30 cm.
buzzerhc_sr04led
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Log motion to an SD card
Accelerometer samples stream into motion.csv on a microSD; the LED blinks while logging.
ledmicrosd_spimpu6050_i2c
A greenhouse controller
The relay closes when the DS18B20 passes 28 °C; an ultrasonic sensor measures distance too.
buttonds18b20hc_sr04ledrelay_1chssd1306_i2c