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DIY - Water Level Alarm for Air Conditioning

In this post, we are going to make a water level alarm for the air conditioning water jug, using an alarm clock. The process is very simple, and the cost is practically zero.

And the thing is, you know. You’re in the living room, relaxed with the air conditioning, and suddenly, everything is full of water! Or worse, the air conditioner starts spraying water like a sprinkler. Well, years ago, tired of this happening in my own room and the water dangerously approaching the tangle of cables of my computer, I decided to make a simple water alarm in the best DIY (Do It Yourself) style.

All we need is an alarm clock of the following style.


You may have some alarm clock of this type at home, as they are very common. They can be bought in bazaars for 2 or 3 euros and are even given away as advertising items.

The bad news is that all these alarm clocks are not exactly the same, so yours will be slightly different. But don’t worry, they are very similar and it’s quite easy.

In general, the process has the following steps,

  1. Disassemble hands and gears.
  2. Remove the motor to prevent battery consumption.
  3. Solder a cable to the alarm switch mechanism.

The alarm we are going to build looks like this in the end (you can click on the different images in this post to enlarge them)


First, we disassemble the clock, remove the plastic casing, remove the front glass, and the hour hands. The alarm clock will be reduced to a box similar to the one in the following image.


Next, we open the clock and remove the gears inside.


At this point, you should have something similar to the following image. We see the motor, and the connection of the alarm mechanism, a simple metal plate that acts by contact. In this clock, a second plastic cover must be removed (it may not exist in yours). We remove it and eliminate the remaining gears.


Now that we have completely disassembled the alarm clock, cut the two motor wires and remove it, to prevent unnecessary consumption. On the other hand, we solder a two-pole cable to each of the points of the metal plate that acts as the alarm switch.


The opposite end of the cable is inserted into a drink straw. Peel and separate the conductors as much as possible, putting them in a ‘T’ shape. In my case, I have opened the straw to prevent any drops from running down the straw and accidentally activating the alarm. I have also made some holes along the straw to prevent it from filling with water when emptying or handling the jug.


At the other end of the straw, we attach a wire, which we shape like the bottle. This wire will function as a clip to hold the probe. To make the clip easily, we bend a piece of wire into a ‘U’ shape, and gently press it against the edge of the bottle until it takes its shape. We join the clip, the straw, and the conductor with a little glue or, if possible, with a heat-sealing gun.


Finally, we just have to attach the alarm clock with insulating tape to our bottle and insert the probe inside. When the water reaches the conductors, the alarm will be activated, warning us that we need to empty the jug.