Accelerator

What We Are Making

A motor which will spin based on
a speed reading from a soft touch pad.

Bits We Need

• 
  Motor
  The visual output for our circuit
• 
  Transistor
  To amplify the current to the motor
• 
  Diode
  A one-way valve for the current
• 
  330Ω Resistor

• 
  Soft Potentiometer
• 
  10k Resistor
• 
  Wires
  To connect everything together!

Motor Overview

Setting up our motor will once again consist of two parts:
the physical components, and the logical components

Physical Components
of the Motor Circuit

Set up your motor as in the diagram.

Logical Components
of the Motor Circuit

• 
  Test Buttons
  One for “off” and one for “on”.
• 
  Arduino Output
  Send the analog value to the motor.

Pass a Message Out to the Arduino

Drag an arduino out node into your workspace and configure it.

Inject a Message

Drag an inject node into your workspace and configure it.

Inject a Message

Drag an inject node into your workspace and configure it.

Connect the nodes

Click and drag the small square on the inject node,
and attach it to the arduino out node.

Deploy Your Code

Click the “Deploy” button in Node Red
to link your logic flow with the Arduino.

Test the Motor Output

The on-screen buttons should turn the motor on and off.

Potentiometer Overview

Setting up our potentiometer will also consist of two parts:
the physical components, and the logical components

Physical Components
of the Potentiometer Circuit

Set up your potentiometer as in the diagram.

Logical Components
of the Potentiometer Circuit

• 
  Potentiometer Input
  Converts the Arduino signal
  into a JavaScript message.
• 
  Debug Logger
  Displays the JS message on
  the screen when received.

Receive a Message from the Arduino

Drag an arduino in node into your workspace and configure it.

Debug the Incoming Data

Drag a debug node into your workspace. The default configuration is fine.

Connect the nodes

Join your arduino node to your debug node.

Deploy Your Code

Click the “Deploy” button in Node Red
to link your logic flow with the Arduino.

Test the potentiometer input

Turn the dial on your potentiometer.

You should see value being logged in your debug panel.

Logical Components
of the whole circuit

• 
  Potentiometer Input
  Receives an Arduino signal
  as a JavaScript message.
• 
  Conversion Function
  Converts the potentiometer signal into the correct message for the LED.
• 
  LED Outputs
  Sends the JavaScript message
  as an Arduino signal.

Circuit Arduino Nodes

Link your arduino input to the three arduino output nodes
via a function, like we did last time.

This time your function requires three outputs instead of one.

Function Code

var pressurePoint = msg.payload;
var lowestSpeed = 130;
var highestSpeed = 255;
var maxPoint = 1024;

if(pressurePoint < 100) {
    msg.payload = 0;
} else {
  var percentTotalSpeed = pressurePoint / maxPoint;
  var speedRange = highestSpeed - lowestSpeed;
  var speedAboveMin = percentTotalSpeed * speedRange;
  var finalSpeed = lowestSpeed + speedAboveMin;

  msg.payload = finalSpeed;
}

return msg;

Paste this code into your function config popup,
in the code editor section.

Shorter Function Code

// mapping function
getSpeed = function(currentPressure) {
  var pressureMax = 1024;
  var motorMin = 130;
  var motorMax = 255;
  var speed = currentPressure * (motorMax - motorMin) / pressureMax + motorMin;

  return speed;
}

msg.payload = (msg.payload > 100) ? getSpeed(msg.payload) : 0;

return msg;

For experienced coders:
This code does exactly the same thing,
but is a bit shorter.

Deploy Your Code

Click the “Deploy” button in Node Red
to link your logic flow with the Arduino.

Full Circuit Test

Press different points on the soft potentiometer.

Your motor should spin at different speeds.