However, suppose I wish to keep the light continuously ON or flash faster like an ambulance light. Then the frequency of the train of pulses sent to light up the LED will be low. If I am using PWM to light up LED lights, and I want slow and gentle dimming lights- kind of like the ones that light up real slow that people use for romantic dates. With regards to PWM, the frequency of the pulses relates to how quickly/slowly, we can get the pulse to the output device. Using this technique, we can simulate an analog output using a digital output. Pulse width modulation or pulse duration modulation is a technique where we vary the width of a square pulse to control the power supplied to any connected device. Controlling the speed of a servo motor using Arduino’s PWM output.Controlling the speed of a DC motor using Arduino’s PWM output.Code for controlling the brightness of an LED and Arduino’s PWM output.Code for controlling the brightness of an LED and Arduino’s PWM output (using a potentiometer).Controlling the Brightness of an LED using a potentiometer.What are the Arduino functions that deal with PWM signals?.What are the PWM output pins on Arduino?. ![]() What are the uses of pulse width modulation?.The motor is connected to a 5V power supply whose ground is shared with Arduino ground. A noise filtering 0.1uF decoupling capcacitor and protection diode 1N4001 from possible back emf voltage spike from the motor are connected across the motor. The DC motor is connected to the transistor collected. A 10KOhm is also connected from the base of the transistor to ground to reduce chances of accidental signal into the sensitive base of the transistor. The PWM pin 10 of Arduino is connected to a 2N2222 transistor via 1KOhm resistor. Here we have connected a 10KOhm potentiometer to the analog pin A0 of Arduino with the other two ends to 5V and ground. Wiring diagram for Potentiometer Controlled DC motor control using PWM of Arduinoīelow you can see the schematic diagram used to control the DC motor speed using potentiometer controlled PWM signal from Arduino. The mapping is simple and we just have to divide by 4. ![]() Once quantization value is collected during one sample time, the value can be mapped to corresponding PWM level which can be from 0 to 255 because PWM is defined by 8-bit resolution and 2^8 = 256 and again taking 0 as count start the PWM level is from 0 to 255.īy mapping the ADC value range 0 to 1023 to PWM levels 0 to 255 we can then send the analog value collected to the PWM level converted value to the PWM pin. The quantization level of 0 corresponds to 0V and 1023 corresponds to 5V. These level values called quantization level from 0 to maximum of 1023 is due to the fact that arduino ADC has 10-bit resolution which gives 2^10 = 1024 quantization level but since count starts from 0 the level is from 0 to 1023. We then read in the analog signal samples using Arduino ADC and convert it to quantization level value between 0 to 1023. ![]() To use potentiometer to control speed, we connect potentiometer to the analog input pin of the Arduino. In this way PWM is used to control the speed of a motor. ![]() The more energy/power is delivered to the motor the faster it will rotate. The more time the pulse stays high the more energy or power is delivered to the motor. If for example, we have a PWM signal with 75% high and 25% low it means that in the total period the pulse stays high for 75% of the time and 25% of the time. By controlling how long the pulse stays high and low during a period we can control how much energy(or power) is delivered to the motor. Duty cycle is the ratio of how long the signal stays high to the total pulse period. PWM is a technique of generating High/Low pulse of different duty cylce. Pulse Width modulation(PWM) with Potentiometer & Arduino
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