Building an Arduino & Node Powered BBQ Thermometer

In the JavaScript Powered Arduino with Johnny-Five post, you walked through the basics of getting an Arduino Uno R3 prototyping platform up and running with NodeJSand the Johnny-Five framework. After configuring Arduino with the “StandardFirmata” sketch, you wrote code with JavaScript and NodeJS, running various versions of LED configurations. This showed several of the core principles of both electronics and software development for the Arduino platform. Having a few blinking LEDs with a button to press, though, isn’t the most exciting thing in the world. So now, in this post, it is time to tackle something fun: a food grade thermometer to monitor the temperature of a steak (or tofu or whatever else) on a grill, and light up an LED when it’s done!

 

upload the code

create a file name blinky.js

This will install the NodeJS package for Johnny-Five, making it available for any NodeJS files in that folder

$npm install johnny-five.

var j5 = require(“johnny-five”);
var board = new j5.Board();
var LEDPIN = 8;

board.on(“ready”, function(){
var led = new j5.Led(LEDPIN);
led.strobe();
});

After successfully,  then you will need the parts list.

• 3/32″ audio input jack (Black 3 Pin 2.5mm Female Audio Mono Headphone Jacks Socket)
• Food Grade Thermometer  (Maverick ET-73)
• Alligator clamp connectors
• 10K Ohm or 100K Ohm food grade thermometer. (I used 200k Ohm)

For this project to work, you must know if it is a 10K Ohm or 100K Ohm thermistor probe. This will inform you of the secondary resistor that you need to use in your circuit. If you have a 10K thermistor, you will need a 10K resistor. If you have a 100K thermistor, you will need a 100K resistor (this post will assume a 10K Ohm thermistor).

I remember when I purchased a different kind of probe was that Maverick ET732/ET733 genuine smoker & chamber probe bbq. It contains higher resistance. One is most hard to deal with it because it making the temperature swing for no apparent reason. You would probably prefer to use the ET-72/73 probes.

Great detail here about HeaterMeter-Probes

In real life, you should set up Arduino right way.

see the code GitHub

For a complete and detailed understanding of these calculations, see the WikiPedia article on thermistors.

Plug It In And Test it

Plug the thermistor probe in to the input jack. Plug the Arduino in to your computer, and run the code:

1	node bbq.js

The LED should be off when the code first starts up, with the actual temperature being logged to the console window:

Now take the thermistor probe, having cleaned it so that it does not have any old food or anything else on it, and hold it tightly between two fingers. The tip is where the temperature is read, so be sure it is firmly in your fingers. The console window should start logging an increase in temperature. Within a few seconds, it should be showing something above 135 degrees and the light will turn on:

Challenges: Solder A Perfboard, Build A Web App

You now have an Arduino powered food thermometer, worthy of any BBQ or cooking station. Well, almost worthy of that. If you really want to use this for some cooking, you’ll want to do a few things to make it stand up to real use:

1. Solder the circuits to a perfboard
2. Build a rocking mobile website so you can monitor the temperatures from your phone, and not just your computer or the LED
3. Put it in a project box

A “perfboard” is a circuit board with hundreds of holes drilled in it, sized for electronics components. Buy a handful of boards, a soldering iron and practice soldering wires in to it before you solder actual components.

For the web application: you’re already using NodeJS, the hipster’s web server. Don’t stop with Johnny-Five. Checkout ExpressJS and Socket.io. See if you can get a web page to show you the current temperature, reported through a websocket.

Once you have it working the way you want, buy a small plastic project box and mount the parts in it. This will help protect the parts, prevent short circuits from things accidentally touching solder joints and leads, and keep everything safe from food splatters while cooking.