## LED Bar Graph The bar graph - a series of?LEDs?in a line, such as you see on an audio display - is a common hardware display for analog sensors. It's made up of a series of?LEDs?in a row, an analog input like a potentiometer, and a little code in between. You can buy multi-LED bar graph displays fairly cheaply, like?[this one](http://www.digikey.com/product-detail/en/MV54164/1080-1183-ND/2675674). This tutorial demonstrates how to control a series of?LEDs?in a row, but can be applied to any series of digital outputs. This tutorial borrows from the?[For Loop and Arrays](https://www.arduino.cc/en/Tutorial/Loop)?tutorial as well as the?[Analog Input](https://www.arduino.cc/en/Tutorial/AnalogInput)?tutorial.  ### **所需硬件** * Arduino or Genuino Board * LED bar graph display or 10?LEDs * Potentiometer * 10 220 ohm resistors * hook-up wires * breadboard ### **電路** click the image to enlarge [](https://www.arduino.cc/en/uploads/Tutorial/BarGraph_bb.png) image developed using?[Fritzing](http://www.fritzing.org/). For more circuit examples, see the?[Fritzing project page](http://fritzing.org/projects/) Schematic: click the image to enlarge [](https://www.arduino.cc/en/uploads/Tutorial/BarGraph2_schem.png) ### **代碼** The sketch works like this: first you read the input. You map the input value to the output range, in this case ten?LEDs. Then you set up a?[for loop](https://www.arduino.cc/en/Tutorial/Loop)?to iterate over the outputs. If the output's number in the series is lower than the mapped input range, you turn it on. If not, you turn it off. /* ? LED bar graph ? Turns on a series of LEDs based on the value of an analog sensor. ? This is a simple way to make a bar graph display. Though this graph uses 10 ? LEDs, you can use any number by changing the LED count and the pins in the ? array. ? This method can be used to control any series of digital outputs that depends ? on an analog input. ? The circuit: ? - LEDs from pins 2 through 11 to ground ? created 4 Sep 2010 ? by Tom Igoe ? This example code is in the public domain. ? http://www.arduino.cc/en/Tutorial/BarGraph */ // these constants won't change: const?int?analogPin?=?A0;???// the pin that the potentiometer is attached to const?int?ledCount?=?10;?? ?// the number of LEDs in the bar graph int?ledPins[]?=?{ ??2,?3,?4,?5,?6,?7,?8,?9,?10,?11 };???// an array of pin numbers to which LEDs are attached void?setup()?{ ??// loop over the pin array and set them all to output: ??for?(int?thisLed?=?0;?thisLed??ledCount;?thisLed++)?{ ? ??pinMode(ledPins[thisLed],?OUTPUT); ??} } void?loop()?{ ??// read the potentiometer: ??int?sensorReading?=?analogRead(analogPin); ??// map the result to a range from 0 to the number of LEDs: ??int?ledLevel?=?map(sensorReading,?0,?1023,?0,?ledCount); ??// loop over the LED array: ??for?(int?thisLed?=?0;?thisLed??ledCount;?thisLed++)?{ ? ??// if the array element's index is less than ledLevel, ? ??// turn the pin for this element on: ? ??if?(thisLed??ledLevel)?{ ? ? ??digitalWrite(ledPins[thisLed],?HIGH); ? ??} ? ??// turn off all pins higher than the ledLevel: ? ??else?{ ? ? ??digitalWrite(ledPins[thisLed],?LOW); ? ??} ??} } [[Get Code]](https://www.arduino.cc/en/Tutorial/BarGraph?action=sourceblock&num=1) ### **參考**: * [pinMode](https://www.arduino.cc/en/Reference/PinMode)() * [for](https://www.arduino.cc/en/Reference/For)() * [digitalWrite](https://www.arduino.cc/en/Reference/DigitalWrite)() * [if...else](https://www.arduino.cc/en/Reference/Else) * [map](https://www.arduino.cc/en/Reference/Map)() * [For Loop Iteration](https://www.arduino.cc/en/Tutorial/ForLoopIteration)?- Control multiple?LEDs?with a For Loop. * [Arrays](https://www.arduino.cc/en/Tutorial/Arrays)?- a variation on the For Loop example that demonstrates how to use an array. * [Row Column Scanning](https://www.arduino.cc/en/Tutorial/RowColumnScanning)?- how to control an 8x8 matrix of?LEDs.