This is the first article of a series for a project with the goal of replacing the electronics in a hot tub from 2005. This Cal Spa tub is over twenty years old! The electronics have started to fail in recent years. Time to replace everything!
I already replaced the secondary pumps controller after it stopped functioning. See this post. Now, the main module is showing signs of failure: the display lights won’t come on, some buttons need “extra” pressure to register action, and the LED lights in the tub are mostly burnt/short circuited. This hot tub was not operational in winter until 2021, but we now use it year round. Even when not in use, the electric and electronic circuits were subjected to harsh conditions. We live in Canada and we get rough winters!
So…
What is involved when replacing all the electronics in a hot tub:
- Safety
- Safety
- Safety
- Managing pump schedules
- Managing water temperature
- Managing LED lightning
- And something new: Managing everything remotely (web interface)
The Hot Tub exposed
But first, lets look at the existing setup:
The hot tub has 5 pumps:
- Main pump 1 – 240 Volts – Variable speed
- Main pump 2 – 240 Volts – Variable speed
- Auxiliary pump 1 – 240 volts – Fixed speed
- Auxiliary pump 2 – 240 Volts – Fixed speed
- Circulation pump – 120 Volts – Fixed speed
The two Main pumps are controlled by a relay circuit from the Main Controller. They are equipped with manual shutoff valve, should they require maintenance. These pumps are standard electrical motors attached to a water pump. All serviceable and easy to detach-reattach.
Main Pump 1 is attached to the heat exchanger (240 Volts – LOTS of current). This pump is the most used as it regulates water temperature. So I have to figure out the sensing technology used for the water temperature and the safety features of the heat exchanger.
Auxiliary pumps are smaller electrical motors attached to a water pump. I have already replaced the control circuit for these pumps. A simple Arduino micro-controller is used to activate a relay to start the motors. See this post. I will replace the Arduino circuit and integrate it in the main circuit.
The circulation pump is a smaller 120 Volt pump that runs 24/7 and is connected to the filter elements. Not much electronics involved here: just a small relay.
The main control board:
Simple technology (relays) but fairly complex electronics. I will have to figure out each circuit component and program a replacement logic. The goal is to eliminate the “brain” of the hot tub while recuperating the activators and relays that are still in good condition.
This has to be done while the hot tub is still operational! As mentioned, the hot tub is kind of OK but starting to fail.
I will post details later, but already, don’t be confused by the vast amount of wires sticking out of the board. Most of it (beige) is 12 or 24 volts relay power.Also, of the 11 visible relays (that I could identify on this photo) only 2 or 3 are used(!). So I will have many spares… Also, on the right side in the middle, you can see a bunch of EMPTY connectors: only one white cable is used to connect to the top panel. The rest of the empty connectors are marked “extra features” I guess I got a simple California Spa with no “extras” attached. TV, sound system, …? There is already FIVE pumps on the spa! How many more do you need?
In the next post, I will start working on the replacement electronics:
The replacement will use microcontrollers and a small computer. I will publish the code in a GitHub.com repository. More on that later.
I will be reusing all the relays and I will find a way to cut the existing “computer circuit” out of the equation.
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