Introduction: How to Use a Servo With Tessel

About: An engineer, seamstress, cook, coder, and overall maker. Spent a summer at Instructables; got a degree in E: Neural Engineering at Olin College; made a microcontroller (; now thinking about climate c…

Tessel is a microcontroller you program in JavaScript. It's like Arduino, but designed to be easier to use and web-friendly.

Here's what you need:

  1. Tessel
  2. Servo module
  3. Servo motor (one comes with the servo module, but there's room for 16 of them on there.)

Step 1: Install Tessel

If you haven't used a Tessel before, you should go install it.

Step 2: Plug in the Servo to the Module

Plug servo into port "1" on the module as shown.

  • the brown wire (ground) goes to -
  • the red wire (power) goes to +
  • the yellow wire (signal) goes to S

Step 3: Power the Module

Plug 5V adapter into the barrel jack on the servo module, then plug into wall power.

Step 4: Plug the Module Into Tessel

It's best to unplug Tessel from power while plugging in modules.

Plug the servo module into Tessel port A with the hexagon/icon side down and the electrical components on the top, then plug Tessel into your computer via USB.

Step 5: Install the Servo Module

Install by typing `npm install servo-pca9685` into the command line.

Step 6: Save the Code

Save this code in a text file called servo.js:

// Any copyright is dedicated to the Public Domain.
This servo module demo turns the servo around
1/10 of its full rotation  every 500ms, then
resets it after 10 turns, reading out position
to the console at each movement.
var tessel = require('tessel');
var servolib = require('servo-pca9685');
var servo = servolib.use(tessel.port['A']);
var servo1 = 1; // We have a servo plugged in at position 1
servo.on('ready', function () {
  var position = 0;  //  Target position of the servo between 0 (min) and 1 (max).
  //  Set the minimum and maximum duty cycle for servo 1.
  //  If the servo doesn't move to its full extent or stalls out
  //  and gets hot, try tuning these values (0.05 and 0.12).
  //  Moving them towards each other = less movement range
  //  Moving them apart = more range, more likely to stall and burn out
  servo.configure(servo1, 0.05, 0.12, function () {
    setInterval(function () {
      console.log('Position (in range 0-1):', position);
      //  Set servo #1 to position pos.
      servo.move(servo1, position);
      // Increment by 10% (~18 deg for a normal servo)
      position += 0.1;
      if (position > 1) {
        position = 0; // Reset servo position
    }, 500); // Every 500 milliseconds

Step 7: Play!

In your command line, `tessel run servo.js`

Watch your servo move!

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