BBQBuddy

an Arduino based, DYI Bluetooth BBQ thermometer with 2 probes (supports up to 4) and a companion Android app.

Overview

Hardware

Battery Usage

Here are the measured amps in various situations:

• 180 mA: Start, phone not connected via Bluetooth
• 160 mA: Bluetooth connected, display brightness 100%
• 130 mA: Bluetooth connected, display brightness 35% (default)
• 115 mA: Bluetooth connected, display brightness 0%
• 85 mA: Bluetooth connected, power save mode (for long cooks)

This gives 30h usage for normal operation mode (130mA) or 47h in power-save mode (85mA) on 2x 2000mAh Nimh AA cells.

Android App

Hardware

Schematic

(Note: Fritzing did not have the same modules I have, I am using pin-compatible ones. See the bill of materials below for the exact list of parts.)

Circuit Board

• TODO: pictures

AVR Code

• Follow Sparkfun's hookup guide to install the board file for Arduino IDE
  • https://learn.sparkfun.com/tutorials/pro-micro--fio-v3-hookup-guide
• Load the Arduino code
  • First, copy the following libraries to your libraries folder
  • Libraries
  • Then, load the project's AVR code
  • AVR Code
• Connect the micro via USB, compile and transfer

Bill of Materials

AVR

• Sparkfun Arduino Pro Micro - 5v/16Mhz
• Make sure to bridge jumper J1, we will be using a separate power supply, no need to waste energy and go through the internal 5v regulator
  • Background: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Dev/Arduino/Boards/Pro_Micro_v13.pdf
• https://www.sparkfun.com/products/12640

Multiplexing 7-Segment Display

• LiteOn LTC-5723wc-10, or similar (options are plentiful, you want the multiplex version with decimal point)
• http://www.datasheetlib.com/datasheet/692818/ltc-5723wc-10_lite-on-technology/download.html

HC-05 Bluetooth Module

• Find these on Ebay or AliExpress

DC-DC Step-Up Converter

• Pololu U1V10F5
• https://www.pololu.com/product/2564

Maverick ET-72/73 Heat Sensors (Thermistor)

• You need two of those
• Buy them as replacement parts for the Maverick ET-71, ET-72 or ET-73 BBQ thermometer
• Easy to find in your local BBQ shop or on Amazon or Ebay
• Background: https://github.com/CapnBry/HeaterMeter/wiki/HeaterMeter-Probes

Passive elements

• 2x 100nF (ceramic)
• 1x 100uF (electrolyte)
• 2x 18k Resistor, 1%
• 1x 10k Resistor, 5%
• 8x 330 Resistor, 5%
• 2x 2.5mm mono socket
• 2x AA NiMH cell
• 1x On/Off switch (print version)
• 1x Battery case for 2x AA cells
• 1x Your favorite stripboard, 2.54mm
• 8x M3 bolts, DIN 965, 10mm
• 8x Mainboard/Circuit-board spacer, M3, 15mm

Casing

• TODO: CAD 2D + 3D screenshot
• TODO: .dxf
• To get the case you see in the picture above, sent the .dxf file to your favourite laser-cut service. The exact materials I used, their thickness and color is specified as comments in the .dxf file.
  • Mine was cut by http://plexilaser.de/, which I highly recommend.

First Use

When you start the thermometer for the first time, look for a Bluetooth device named "HC-05" on your phone, and pair it with pin "1234". When you start the thermometer app, it will automatically connect to the HC-05 device and you are ready to go.