Introduction: SMS Tank Overflow Alert

Water tank overflow is a major problem in most of the homes these days (not in appartments). Ofcourse there are such alarms to prevent this problem but still, they are not that effective. This is almost the same thing but much smaller and with better features, the best one being that instead of an audio or visual signal, this one gives you an SMS alert to your phone as the tank gets full! This should be a much better option, isn't it? If not, then you can just build it as a cool weekend project just to satisfy your desire to MAKE it yourself!

This one uses the Mediatek Linkit ONE, an awesome prototyping platform with loads of features. As you just have to send a text message, this one uses the GSM feature to give you an alert no matter where you are in this world. For overflow detection, it uses that old yet effective transistor circuit with two wires moving towards the tank. Some people would have a doubt that combining electricity and water can be risky, but you needn't worry as this one has no such risks unless you throw your Linkit ONE inside water ;). So why to wait? Let's begin!

You can vote for this project if you like the concept and documentation and can even LIKE my facebook page- Frozen Solenoid for more cool projects, videos and facts.

Step 1: How It Works?

First, starting with the working of this project. The main process, as already explained in the introduction part is that the Linkit ONE will send you a text and will ring a buzzer + glow an LED as soon as it detects that the water tank is full.

The first part is the water sensor board that actually detects water after it has reached a certain level to prevent an overflow. You may already know that tap water is a fair conductor of electricity (neither too good, nor too bad). Now using this fact and placing two wires inside the tank at a certain level, we can easily detect the level of water as when the water will reach that level, it will act as a conductor or simply a resistor and join the other two wires completing the circuit. As water has a quite high resistance, I have used a transistor to detect even very small current that will flow through and give the output to linkit ONE accordingly.

Rest of the part is pretty straightforward. As the Linkit ONE gets a output from the transistor, it sends an SMS to your phone through it's built-in GSM feature. But you should also have a SIM card inserted to actually make it work. I have also added an LED and a buzzer to give audio as well as visual indications along with an SMS alert.

Step 2: Parts and Tools

The following parts and tools will be required by you to make this project. You can simply order them from any electronics hobby online store. The total cost of all the parts was approx. $70 or 4200 INR.


  • 1x Mediatek Linkit ONE
  • 1x Linkit ONE battery
  • 1x GSM antenna
  • 1x LED (optional)
  • 1x Buzzer (optional)
  • 1x SIM card (shouldn't be pin-locked)
  • 1x BC547 or any other appropriate NPN transistor
  • Male headers
  • Perfboard
  • Some wire
  • A base for assembling your project


  • Soldering iron
  • Soldering iron
  • Double sided tape
  • Helping hands
  • Wire cutter/stripper

Step 3: Make the Water Sensor Board

Now here we start with the process of building this project. The very first step, rather an important one is to make the water sensor board that consists just a transistor along with a buzzer and LED which are optional.

On a tiny little piece of perboard, solder all the components as per the schematic given above. Two wires will go towards the water tank and a screw terminal must be soldered to connect them.

Three of the wires will go towards linkit one. They are- GND, 5v and Output. Solder a male header for each one of them so that you can connect them later easily. You can even solder a buzzer and LED for audio as well as visual overflow indications but this is not mandatory. The project would still work without them.

Step 4: Connect the Board to Linkit ONE

After soldering your board, connect it to linkit one as per the following. You can even follow the schematic provided above.

  • Vcc from board ----- 5v of linkit one
  • Gnd ----- Gnd
  • Vout ----- Analog pin 0 (A0)

Step 5: Connect the Antenna, Battery and Insert a SIM Card

This one's easy! You just have to connect three very basic things.

  1. First insert a SIM card to the SD/SIM combo at the back side of the board. You should make sure that your sim in not pin-locked else it wouldn't work.
  2. Then connect the GSM antenna (the bigger black one) to it's respective socket again at the back side of the board.
  3. Lastly connect the lithium battery through the white socket present on the board.

Step 6: Arrange Everything on a Base

After doing all the connecting and soldering, now you have to place everything on a base to make things clean and to prevent any connections from breaking.

You can even enclose all the parts in a sturdy enclosure. I chose a thick wooden base and stuck all the parts on it cleanly using some double sided foam tape.

Step 7: Upload the Code

Upload the code provided in the ino file present below to your Linkit ONE. But before uploading, should take care of two things:

  1. The switches on the board should be in SPI, UART and USB positions else the code wouldn't upload. Look for three little switches present on the board itself.
  2. In the line: LSMS.beginSMS("0123456789") CHANGE those numbers to your original number.

Step 8: Take a Test

An optional step, you can take a small test before installing it on your real water tanker. For this, first go get a mug. Then follow these steps:

  1. First take two long pieces of wires and connect them to the screw terminals on your sensor board.
  2. Tape the other two ends inside the mug such that both of them don't touch each other and are at the same level. They should also be just at a level little than the maximum level.
  3. Now check everything and then switch the device on by setting the switch to BAT position.
  4. Fill the mug completely with water.

Now you would see that as you fill the water at it touches the two wires, the buzzer would beep along with the LED glowing. Now go and check your phone. Whoa! You would see a text message from this device saying that your tank is almost full!

Step 9: You're Done

This brings this instructable to an end. Hope you liked it. Please feel free to suggest some modifications to make it better and to correct my errors and do leave a feedback in the comment section below. Follow me and vote for this project if you really linked it!

Please like my facebook page- Frozen Solenoid for even more awesome projects.

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