Tim Mikkelsen's Arduino Projects


2016/05 Thing Dev Hot Tub button remote


My wife and I have a cabin that has a hot tub.  The one thing that I wanted to do was to have a way to set the temperature remotely.  

SparkFun has a small Internet of Things (IoT) development (Thing Dev) board that seemed to be just the thing.  It has worked out so far and this is the breadboard experiment for the project.    

The Thing Dev is an Arduino compatible system linked to an ESP8266 WiFi system on a chip (SoC).  Basically, it provided all the needed infrastructure.  The only additional hardware needed were relays and related hardware to simulate key presses on the Jacuzzi key pad.  I did also add a temperature sensor to connect to the pipes to get a reading on the current hot tub temperature.  

The web page that gets served up has:


     current temperature in Farhenheit and Celsius

     a button for refresh

     a button for minimum temperature (80F)

     a button for maximum temperature (104F)


  - Sparkfun WRL-13711 - an ESP8266 Thing Dev Board

  - Sparkfun SEN-10988 - a TMP36 temperature sensor

  - Sparkfun COM-00100 - 2x SPDT sealed relays

  - Sparkfun COM-13689 - 2x P2N2222A NPN transistors (BC337)

  - Sparkfun COM-08589 - 2x 1N4001 1A/50V small signal diodes

  - Sparkfun COM-08377 - 2x 330 ohm resistors

  - Sparkfun TOL-12890 - USB wall power supply

Total parts cost: Approximately $40

Thing Dev / Hot Tub control code


Temp Sensor Data Sheet

Relay Data Sheet

Thing Dev Data Sheet

A few comments:

1. The Thing Dev only has one analog input and it measures 0-1 volt.

2. The WiFi, networking, and embedded HTML was a bit convoluted and took me a bit to get it figured out.

3. I've left the serial debug code in the project, because you really need to see what's happening...  

4. I have thought about doing a Raspberry Pi version with a pair of I2C temperature sensors (to have outside and tub temperature).  But this is overkill for the desired functionality but it does allow for other functionality (like having an .mp3 music player/library built in).

5. In the process, the circuit worked just fine.  However, the Jacuzzi J370 hot tub has a sealed topside controller and I didn't want to destroy it in the process.  I tried to figure out the cabling but the connection is some sort of serial digital signal.  When I tried to insert and interface with the digital, it interfered with the signal.  So this didn't work.