{"id":24233,"date":"2019-09-05T14:41:21","date_gmt":"2019-09-05T06:41:21","guid":{"rendered":"\/blog\/?p=24233"},"modified":"2020-11-04T12:24:56","modified_gmt":"2020-11-04T04:24:56","slug":"get-started-with-the-grove-16-channel-pwm-driver-pca9685-and-control-your-own-robotic-arm","status":"publish","type":"post","link":"https:\/\/www.seeedstudio.com\/blog\/2019\/09\/05\/get-started-with-the-grove-16-channel-pwm-driver-pca9685-and-control-your-own-robotic-arm\/","title":{"rendered":"How to use Grove – 16-Channel PWM Driver (PCA9685) to Control Robotic Arm!"},"content":{"rendered":"\n

Have you ever encountered the situation where you want to build your own robotics projects using an Arduino, but failed to do so with only just an Arduino because of the limited number of PWM outputs it has? <\/p>\n\n\n\n

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The solution to this will be to use a PWM driver such as the Grove – 16-Channel PWM Driver (PCA9685)<\/a> which is a 12-bit PWM driver based on the NXP PCA9685 and can drive up to 16 servos with an external power supply of 5V. This PWM Driver can also be used to control LEDs. <\/p>\n\n\n\n

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Grove – 16-Channel PWM Driver (PCA9685) <\/figcaption><\/figure><\/div>\n\n\n\n

When you want to connect more than 16 servos at the same time, you can connect these drivers in series for up to 62 drivers which will be connected to the same I2C bus. <\/p>\n\n\n\n

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What is\nPWM?<\/strong><\/h2>\n\n\n\n

PWM stands for\nPulse Width Modulation. Normally there are two different kinds of signals:\nDigital and Analog. Digital signals are \u201c0\u201d or \u201c1\u201d, \u201cOFF\u201d or \u201cON\u201d and Analog\nsignals can be ON, OFF or have an infinite number of positions between 0 and 1.<\/p>\n\n\n\n

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Digital vs Analog Signal<\/figcaption><\/figure>\n\n\n\n

Computers can only understand 0\u2019s and 1\u2019s which is digital. So finally, the MCU (Microcontroller Unit) can only understand digital input. Once you have Analog inputs from your sensors, the Analog signals (ex: – from temperature sensors) have to be first translated into Digital signals through an Analog-to-digital converter and then the MCU can recognize that signal.<\/p>\n\n\n\n

On the other hand, PWM can be explained as the reverse of that. It is a way of controlling analog devices using a digital output. But PWM is not truly an Analog output, however, it pretends to be an Analog like the signal result, by applying power in pulses.<\/p>\n\n\n\n

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Here is an example to explain it further:<\/strong><\/p>\n\n\n\n

Apply maximum\nvoltage to a motor for a brief amount of time, and then turn it off. Repeat\nthis by changing the time interval between the turning off and turning on. Even\nthough we are applying and removing voltage many times within an interval, it creates\na response which is near to being Analog. <\/p>\n\n\n\n

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Blue Lines are PWM outputs from MCU whereas the Red Line is the average voltage<\/figcaption><\/figure><\/div>\n\n\n\n
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How\nservos are controlled using PWM?<\/strong><\/h2>\n\n\n\n

A Servo\nMotor is a low-speed, high-torque motor and comes in different sizes. These\nmotors are often limited to the following rotation angles: 180, 270 or 90 degrees and are\ncontrolled by an electrical signal which determines the amount of movement of\nthe shaft. This signal is a PWM signal and the amount of movement of the shaft is\ndependent upon the duration of the pulse sent via the control wire.<\/p>\n\n\n\n

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Diffrerent Types of Servo Motors<\/figcaption><\/figure><\/div>\n\n\n\n

Normally a servo\nmotor expects to see a pulse every 20 milliseconds (ms) and the length of the\npulse will determine how far the motor turns. For example, a 1.5ms pulse will\nmake the motor turn to the 90\u00b0 position. Shorter than 1.5ms moves it in the counterclockwise\ndirection toward the 0\u00b0 position, and any longer than 1.5ms will turn the servo\nin a clockwise direction toward the 180\u00b0 position.<\/p>\n\n\n\n

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How to test the Grove – 16-Channel PWM Driver (PCA9685) with a single servo motor?<\/strong><\/h2>\n\n\n\n

Hardware\nNeeded<\/strong><\/h4>\n\n\n\n