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| Hot Tub Controller Circuit Board |
The controller is built to mount on top of a Raspberry Pi and does the following:
● Monitor the water temperature
● Turn a circulation pump and heater on to heat the water as needed
● Respond to buttons that increase/decrease the desired temperature
● Respond to buttons that turn the water jets on and off
● Display the current temperature
● Detect various failure modes and place system in safe mode
● Listen for commands from a smart phone app to control hot tub
● Detect various failure modes and place system in safe mode
● Listen for commands from a smart phone app to control hot tub
● Upload data periodically to an Internet of Things service
Temperature monitoring is performed by a waterproof DS18B20 from Adafruit. It uses a simple 1-wire bus to read the data.
The display, also from Adafruit, is a 7-segment LED display and is controlled using an I2C bus.
The device is powered by a 24V DC power supply since the relays on the hot tub are controlled by a 24V signal. A 5V step down regulator provides power to the Raspberry Pi.
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| Relay Control with LED Indicator |
The push buttons are connected to GPIO inputs which drive interrupts. These require "debounce" conditioning and this is explained in this post.
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| Smart Phone app for Hot Tub |
The Internet of Things support is using ThingSpeak and the method is described in this post. You can see the live data at this URL.
The system also listens on a network socket for incoming commands from a smart phone app that allows me to monitor and control the hot tub remotely. It's actually not an app, rather just a web page designed for a mobile screen. This way it can easily be used by my Android, my wife or son's iPhone, or from any web browser.
Here is a video showing the completed controller in action.
And, yes, I really do keep my hot tub that hot. One advantage of making my own controller is that I am not limited to 104 degrees max.