Fig.1 – The switching PSU
This is the PCB I used to test all my projects.
When I drew it, I took the cue from the project published on electroniq.net (I hope the attribution is made to the right author because I found many clones on the internet). I changed something on that schematic making the improvements I thought were right also in order to try to use the components I already had available.
To be honest, what makes the project so good is not this specific schematic. That is nothing more than an elaboration of some “typical applications” suggested on the L296‘s data sheet, but the IC itself.
The l296 switching regulator requires very few external components and the current limiter is already inside it (make sure to use the L296P to take the advantage of this function).
If you are interested in buffering for a short time frame (ex. a holiday) this is the right solution for you, otherwise go to the project BP005 for a self-controlled watering system that operates 365 days per year.
Fig.1 – The watering system’s central unit
Some years ago I had the opportunity to spend a whole month holiday in Portugal. I didn’t want to ask my friends, or neighbours, to water my plants everyday for me. I thought therefore to build a system for that purpose using the most common microcontroller PIC16F84A.
I thought and tested lots of different solutions in order to find the best one. Reliability was the most important aspect to ensure: a fault could have killed my plants or, worse, flooded my neighbour’s house. Once the system was built, only a few days remained before my departure. So, I set the irrigation timing as best as I could, I asked a friend of mine to go and check once if everything was fine and I left the house crossing my fingers.
To ensure a proper function of a system, keeping the temperature of all devices within their working values is very important. Since a common working range of temperature is about from -20°C to +85°C, the lower limit is generally negligible. On the contrary, the higher level could be a problem since all the devices, some more and some less, tend to increase their inner temperature. In certain situations, especially in power circuits, it is necessary to use some cooling devices in order to cool down the hot ones and make the environment well ventilated.