Water Tank Monitoring System Is Now Slug-Proof

[Peter] is doing his part toward protecting the environment and conserving water. He’s built a rainwater collection system complete with an underground storage tank. Since he wanted to monitor the water level in the tank, he made a level indicating system. Everything was going well until one day out of nowhere it stopped working, only returning 0’s as the level. [Peter] took a look and found that I slug had made its way into the electronics enclosure and slimed up the traces on the PCB, causing short circuits.To fix the problem [Peter] decided to redesigned the system. This time it would be built into an all-weather electrical box. The system uses a standard hobby ultrasonic range finder to measure the distance from the top of the tank to the level of the water. Two holes cut into the electrical box allow the sender/receiver components to peek outside of the enclosure. Any gaps were then filled with sealant. [Peter] also added a thermistor to measure the temperature inside the tank.The sensor values are read by an Arduino and sent wirelessly to [Peter]’s computer via a pair of XBee’s and a second Arduino with an ethernet shield. The data are sent in 3 minute intervals and automatically stored in a MySQL database for quick reference of level and temperature trends. Now [Peter] can monitor his rain water remotely and adjust his usage habits accordingly. Want to read more about water tanks? Check out this overflow monitor system.

24 thoughts on “Water Tank Monitoring System Is Now Slug-Proof

  1. I slug? Like I-Robot, but with a bit more gastropod? Perhaps it’s roman numerals? Sorry, I’m being pedantic, but reading over errors like that breaks my immersion in the discussion of the hack

          1. That’s arguably correct, as datum is the singular and data the plural, though common usage is gradually phasing out the use of datum, and is using data instead.

  2. I really love that 3D picture in the site. I wish more people would use that. Cross eyed 3d is amazing once you get the hang of it. It really gives your brain good info too. I take 2 pictures many times so (one for each eye) I can view them in 3d later.

    I check my water level in my aquaponics by a simple probe made of cat 5 wires.
    In two years, they haven’t corroded because I only sample once a second.

  3. I have worked a lot with these sensors during my phD in hydraulics and im abit scared that in time the system will fail again, since the sensor will be hanging above the water surface all the time, and thus corrosion will get a hold of them.
    Furthermore i wonder whether he uses the thermistor to calculate the sound velocity, since it is (highly) temperature dependent.
    I also found out that the accuracy of the device shows some strange behaviour, which can be backtracked to the applied measurement frequency, resulting in the fact that the device cant measure more precise than 4/5mm resolution.


    In my setup I also have the sensors in a electrical enclosure, coupled with a custom made pcb (by hand) with an underclocked chip at 8Mhz in order to save battery, and a nrf24l01 for the communication.
    It measures every 5 seconds, and goes to sleep in between .
    The sensor goes into deep sleep itsself when the base station is not up, and pings for a connection every minute.
    If I remember correctly the system uses about 40µA of my 2 1,5V batteries while up, and about 6µA when in deep sleep.
    This gives me incredible flexibility and long battery life.
    The option that the deep sleep sets in if the base station is turned off is very handy, since we dont need a 24/7 monitoring, and this way no-one can forget to put the devices off.

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