Due to being often travelling away from home, I thought it would be a good idea to water my plants automatically.

What I had in mind was to set up an irrigation system using pipes, solenoid valves and a control system to detect soil moisture.

Setting up the piping was not a big problem as these were readily available. I can use PVC pipes and glue them in place.

Hole puncher making a hole at the HDPE pipe of irrigation system

Hole puncher making a hole at the HDPE pipe of irrigation system

But what I found out later was the problem of how to distribute the water to the various pots holding my plants. It is not as easy as it seemed. First off, I can drill small holes on the pvc pipe to let the water flow out and drop into the pots. Initially I did that, but found that it did not work as well as I wanted. The water flow was not easily controlled and was not consistent.

Nozzle for Irrigation System

Nozzle for Irrigation System

I later found that by using hdpe pipes, which was softer than pvc pipes, I can actually fix nozzles to them without any need for screw thread or glue. These nozzles could be connected to small hoses which can then be directed to near the roots of the plants. Essentially, the water would be in small amounts so that it would not be wasted. In fact, irrigation systems using this method can precisely use only minimal amounts of water and is very effective in dry arid regions.

Nozzle connected to HDPE pipe

Nozzle connected to HDPE pipe

As usual finding the 1/2 inch pipes and their connectors was not a problem at all. Those hardware shops that stock pvc pipes also stock hdpe pipes and their connectors. They are readily available at any hardware shop. The challenge is to find the nozzles that can be attached to the pipes without leaks. By searching on the internet, I managed to find a supplier and completed the piping set up. These nozzles were quite unique in the sense that they are only held in place by the barb at the end of the nozzle and the leaks were prevented due to the natural contraction of a hole punched on the hdpe pipe. Once the nozzle was forced in, it remained in place and there were no leaks.

Commercial watering systems use a timer to manage the watering. With a 24-hour timer set to operate for a few minutes everyday, coupled with reducing valves for pressure control, needle valves for flow control, back-flow valves in case of distribution to higher areas than the source and other accessories the whole system could be quite costly.

Transparent PVC Flexible hose connected to nozzle of HDPE main pipe

Transparent PVC Flexible hose connected to nozzle of HDPE main pipe

My idea is to do it automatically, i.e. only water when the soil needed it. With a timer system, the watering will start even when the soil is soaking wet. This will not do.

So I found an electronic soil moisture detector circuit using a transistor and hooked up the wiring together with the power supply and a relay. For the solenoid valve, I used a salvaged part from an old discarded washing machine. The switching power supply was also salvaged from somewhere, perhaps previously meant for some other electronic equipment. At the time of writing, the whole system was working, except for the fact that for a lack of parts, I had substituted a fixed resistor in place of a variable resistor when I was testing the circuit. And it had worked on the test bench.

Irrigation system using HDPE pipe

Irrigation system using HDPE pipe

However, when it was hooked up to an actual wire with sensing terminals, the resistance of the setup with a naturally different value did not work properly. This is quite an essential part, as the biasing of the transistor need to be adjusted in order for it to function properly. I had bought the variable resistor, but did not have the time to hook it up. (After all, the rainy season was beginning and there was no urgency to make the watering system work)

More will come later…