Lesson 5--Microduino “LED Brightness and Potentiometer PWM”

Objective Last lesson we use the button to generate PWM to control the LED, this lesson we will use precision potentiometer to control the LED. The deffience between them is that the button use the digital voltage signal (0 and 1) to control which only has two states. When the signal changed,LED increases brightness by 5 units (0 ~ 255). Potentiometer use the analog voltage to generate PWM which is a linear change of state, so the LED's brightnees can be changed coherently and softly. Conversely,if use the button, you need consider the button shaking. Equipment Microduino-Core Microduino-FT232R Other hardware equipment Breadboard Jumper one box Breadboard one piece LED Light-emitting diodes one 220Ω resistor one Precision potentiometer one USB Data cable one Experimental schematic File:第五课-原理图.jpg 600px Connection method, LED connects to the PWM output pin, and potentiometer connects to analog port A0 ~ A5. Analog interface can measure 0-5V voltage, and the corresponding return value is 0-1024, the measurement accuracy of the voltage variation is relatively high. Potentiometer had better choose winding precision linear potentiometer, because some cheap nonlinear potentiometer on the market doesn't have a good electrical characteristics. numerical drift is big which easy to cause the led flashing, Resistance is nonlinear variation, so the brightness change is not obvious, easy to produce the sense of hierarchy just like the button dimmer experiments, impact the test results. Program 　　　void setup() 　　　{ 　　　 pinMode(3,OUTPUT); //Choose the PWM output Port 　　　} 　　　void loop() 　　　{ 　　　 int val= analogRead(A0); //Read the analog port A0's value（voltage range is0-5V,corresponding value is 0-1204） 　　　 val = map(val, 0, 1023, 0, 255); 　　　//Mapping the analog value（0~1024）to（0~255），the Max PWM value is 255。 　　　 analogWrite(3, val); 　　　 //analogWrite(11,val/4); //The max PWM value is 255，so the analog value is divided by 4. 　　　} map() function Function： Map a certain range values to a different range Grammer：map(value, fromLow, fromHigh, toLow, toHigh) value：return value fromLow: Paternal interval lower limit fromHigh：Paternal interval upper limit toLow：Mapping range lower limit toHigh：Mapping range upper limit Result With the rotation of the potentiometer, LED brightness changes softly. Video