ESP8266 NodeMCU with TDS Sensor (Water Quality Sensor)
In this project, you'll learn how to use an ESP8266 NodeMCU board with a TDS meter (Total Dissolved Solids). A TDS metre shows the number of salts, minerals, and metals that have dissolve…
Know the mission before touching a wire.
Understand what you are making, prepare the right tools, and make the workbench safe.
Project details
ESP8266 NodeMCU with TDS Sensor (Water Quality Sensor) is a iot project. In this project, you'll learn how to use an ESP8266 NodeMCU board with a TDS meter (Total Dissolved Solids). A TDS metre shows the number of salts, minerals, and metals that have dissolve…
- Source pages
- 954-957
- Named parts
- 4
- Build goal
- Working, tested prototype
Tools you need
- Digital multimeter
- Wire stripper and side cutters
- Soldering iron with a fine tip
- Current-limited bench supply
- Computer with a data-capable USB cable
Use eye protection, good lighting, and a clean insulated surface throughout the build.
Safety precautions
- Disconnect every power source before changing a connection.
- Check component polarity, pinout, and supply voltage twice.
- Use a current limit for the first power-up.
- Keep liquids, loose metal, and uninsulated wires away from the bench.
Gather, identify, and understand every part.
Use the standardized inventory, then open What's this? to learn each part's role, advantages, limitations, handling, and specifications.
What's this?Image, role, pros, cons, handling & specifications
ESP8266
A programmable controller that reads inputs, makes decisions, and drives the project's outputs.
What it does hereIt is the control centre and must use the documented board, pin map, supply, and logic level.
Buy / compare this part ↗Advantages
- Reprogrammable and reusable
- Large learning ecosystem
- Complex behaviour remains changeable
Limitations
- GPIO voltage and current are limited
- Some pins affect boot or communication
- Loads normally need a driver
Handling
- Disconnect power before rewiring
- Avoid static discharge
- Never power motors, relays, or pumps directly from GPIO
Specifications to verify
- Use the exact model, value, package, and rating listed for ESP8266; similar-looking parts are not always interchangeable.
- Confirm operating voltage, logic level, pinout, memory, USB interface, and maximum GPIO current.
What's this?Image, role, pros, cons, handling & specifications
MODULE LEARNING VIEWNodeMCU
A programmable controller that reads inputs, makes decisions, and drives the project's outputs.
What it does hereIt is the control centre and must use the documented board, pin map, supply, and logic level.
Buy / compare this part ↗Advantages
- Reprogrammable and reusable
- Large learning ecosystem
- Complex behaviour remains changeable
Limitations
- GPIO voltage and current are limited
- Some pins affect boot or communication
- Loads normally need a driver
Handling
- Disconnect power before rewiring
- Avoid static discharge
- Never power motors, relays, or pumps directly from GPIO
Specifications to verify
- Use the exact model, value, package, and rating listed for NodeMCU; similar-looking parts are not always interchangeable.
- Confirm operating voltage, logic level, pinout, memory, USB interface, and maximum GPIO current.
What's this?Image, role, pros, cons, handling & specifications
Temperature sensor
A sensor converts a physical condition into an electrical signal the circuit can measure.
What it does hereIt provides project input as an analogue, digital, resistive, frequency, or calibrated signal.
Buy / compare this part ↗Advantages
- Adds real-world awareness
- Can usually be tested independently
- Often supports calibration
Limitations
- Readings can drift
- Placement affects results
- Some sensors need warm-up or calibration
Handling
- Protect the sensing surface
- Observe supply voltage and polarity
- Keep signal leads away from noisy power wiring
Specifications to verify
- Use the exact model, value, package, and rating listed for Temperature sensor; similar-looking parts are not always interchangeable.
- Confirm supply range, output type, measurement range, accuracy, response time, and pin order.
What's this?Image, role, pros, cons, handling & specifications
NETWORK
A named project component whose exact role is defined by the source circuit and build guide.
What it does hereIt performs a documented electrical, control, interface, or construction function in this project.
Buy / compare this part ↗Advantages
- Selected for this project
- Can be checked independently
- Supports modular troubleshooting
Limitations
- Substitutes may differ
- Generic names can hide variants
- Pinouts and ratings vary
Handling
- Compare the received part with the source
- Keep it labelled
- Do not force connectors or adjusters
Specifications to verify
- Use the exact model, value, package, and rating listed for NETWORK; similar-looking parts are not always interchangeable.
- Confirm dimensions, ratings, connection method, polarity, and environmental limits.
Connect one verified path at a time.
Explore the named components and standardized signal flow, then use Source Check to verify exact physical pins, values, and topology before applying power.
Trace this circuit.
ESP8266 NodeMCU with TDS Sensor (Water Quality Sensor): interactive parts, standardized terminals, responsive anchored wires, student explanations, and the original circuit reference in one shared system.
Trace before wiring
Follow power, ground, inputs, processing, and outputs in that order. Never guess a pin from package shape alone.
Connect with power off
Make short, labelled connections and share a common ground only where the schematic requires it.
Inspect every joint
Check continuity, polarity, adjacent shorts, and loose connections before the first power-up.
Open all source diagrams and build views 3 visuals
Confirm the hardware-only control path.
This project does not include firmware in the source. The circuit itself provides the required behaviour.
How to connect
- Match every controller label to the circuit view and source pin map.
- Join grounds before signal wires when separate low-voltage supplies are used.
- Keep motors, relays, pumps, and other loads on a suitable driver and external supply.
Common mistakes
Reversed VCC/GND, board-label versus GPIO-number confusion, missing common ground, and charge-only USB cables.
Troubleshoot
Disconnect loads, continuity-test one path at a time, then test with a current limit.
Software preparation
No IDE, board package, library, or firmware upload is required for this project.
If you add a programmable controller as an extension, document its pin map separately.
How to upload code
The original design is implemented entirely in hardware, so proceed after verifying the circuit and supply.
Assemble, deploy, test, and troubleshoot.
Use the complete source notes in build order, then pass the final checks before calling the project finished.
Build in functional stages
- Power and regulation
- Controller or processing stage
- Inputs and sensors
- Outputs and loads
- Enclosure and strain relief
Power up safely
- Inspect unpowered continuity first
- Apply the lowest safe current limit
- Measure supply rails before signals
- Add one load at a time
- Record expected and actual results
Work from simple to complex
- Confirm power, ground, polarity, and orientation
- Compare each pin with the source
- Test inputs separately from outputs
- Replace only one variable at a time
- Power off before every correction
Follow the documented instructions.
These notes come from this project's source and remain in their original order.
Project overview
Project build noteIn this project, you'll learn how to use an ESP8266 NodeMCU board with a TDS meter (Total Dissolved Solids). A TDS metre shows the number of salts, minerals, and metals that have dissolved in a solution. You can use this parameter to get an idea of how good the water is and to compare water from different sources. One of the main uses of a TDS metre is to check the quality of the water in an aquarium. We'll use the TDS metre from keystudio to show you a simple way to use Arduino IDE to measure TDS in ppm units. Introducing the TDS Meter A TDS metre counts the number of salts, minerals, and metals that have been dissolved in water. As the number of dissolved solids in water goes up,
so does the conductivity of the water. This lets us figure out the total amount of dissolved solids in parts per million (mg/L). Even though this is a good way to check on the quality of the water, keep in mind that it doesn't measure contaminants. So, you can't just look at this sign to figure out if the water is safe to drink or not. A TDS metre can be used to check the quality of water in pools, aquariums, fish tanks, hydroponics, water purifiers, and many other places.
Features and Specifications This guide talks about the keystudio TDS Meter V1.0. Here are the settings
TDS Meter
Project build noteInput Voltage: DC 3.3 ~ 5.5V Output Voltage: 0 ~ 2.3V
Current at Work: 3 to 6mA TDS Measurement Range: 0 ~ 1000ppm Accuracy of TDS measurement: 10% F.S. (25 °C) Module Interface: XH2.54-3P Electrode Interface: XH2.54-2P
TDS Probe
Project build noteNumber of Needle: 2 Length as a whole: 60cm Connection Interface: XH2.54-2P White: Color Waterproof Probe
Interfacing the TDS Meter with the ESP8266 The TDS meter sends out an analogue signal that can be measured with the analogue pin A0 on the ESP8266. The TDS Meter, which is based on the ESP8266 microcontroller, connects to a Wi-Fi network and continuously transmits data to the Blynk application. You are able to obtain a report concerning the quality of your water around the clock. Therefore, the TDS sensor is the most effective sensor for monitoring water quality. Connect the sensor as shown in the following table. TDS Sensor ESP8266
DATA A0
Project build noteIf the probe is not in the water, it will show a value close to 0. Check the TDS of a solution by putting the probe on it. You can use tap water and salt to see if the values go up. The TDS value of the tap water in my house is about 100ppm, which is a good value for drinking water. I also tested tea and found that the TDS value went up to about 230ppm, which seems like a good number. Lastly, I measured the TDS value of bottled water and found that it was about 25ppm. A TDS meter can figure out how many solids are in a solution as a whole. It can be used to tell how good the water is and to describe what it is like. The meter tells you how much TDS there is in parts per million (ppm) or mg/L. The TDS value can be used for many things, but it can't be used alone to tell if water is safe to drink or not. A great way to use this kind of sensor is to check the quality of the water in an aquarium. You can keep an eye on your fish tank with this sensor and a waterproof DS18B20 temperature sensor.
You built ESP8266 NodeMCU with TDS Sensor (Water Quality Sensor).
You followed the full workflow from understanding the mission to testing the finished project. That is a real engineering achievement - well done.
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