TDS is monitored to ensure the quality of your RO/DI water, this will help you decide when to change the filters.​ The sensor generally has a small PCB which is mounted in the sensor module and a probe for the tank water.
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The TDS sensor is an Analog sensor and can only be conected to one of the Senosor module analog ports.
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Here is how to set one up....
TDS Sensor
Analog sensor
A TDS (Total Dissolved Solids) sensor measures the concentration of dissolved substances, like minerals and salts, in reef aquarium water. It works by sending an electrical current between two probes and measuring the water's conductivity, which increases with higher dissolved solid levels. The sensor converts this data into a TDS value (ppm), indicating water purity. It's commonly used to monitor RO/DI filter performance and ensure clean, stable water for reef health.
Hardware conection
How its conected
The TDS sensor needs to be connected to one of the analog ports in the sensor module, each port can supply either 5v or 3,3v to power the sensor. For the signal there is a 3 port teminal, the center port is Ground then either side are the Signal pins. Signal can either be sent directly (DIR) to the ESP32 or via a voltage divider (DIV). The ESP32 can only read analog volages up to 3v so if you have a sensor that outputs more then you will need to use the divider.
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Here is an example of how to use the divider:
5v analog output form sensor reduced to 3v for the esp32. R1 = ?Ohm R2=?Ohm
Software setup
Checking the Code
Analog sensors require a little more setup on the Software side, you will have to enter a few details and do some calibrations to get it working corectly.
Setup the code:
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Calibrateion:
Links
Here are a few links to where you can purchase your sensors, click the link depending on your location.
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Worldwide link generally takes longer to be delivered but is a little cheaper. Better if you want to bulk order.
Full disclosure: some of these links are affiliate links, clicking them and purchasing though my links helps me support the project.
Worldwide
Worldwide Link
USA
USA Link
UK
UK Link
Europe
Europe Link