My Smart Sprinkler System Part 2.

Introduction
You might be aware that I have been frustrated about forgetting to switch off appliances before leaving home. I guess its a sign of old age, my forgetfulness is becoming fairly pronounced. but instead of grumbling, as a technological determinist, I decided to create a smart home.

I have been tinkering with microcontrollers for some years, but creating a smart home got me jumping into the deep end of Internet of Things IOT. I have short listed several projects that I will need to create to have a smart home, and you can find them from looking through my blog for IOT and my smart home. here -

As you can see I have a whole lot of projects to keep me busy for a long long time. but not to worry, they are all simple modular systems that latch unto each other to create a smart system. I usually, will share them here with you. you can follow the steps and recreate them for yourself if you have the basic skills of soldiering and following simple instructions. I will also share Gerber files, circuit diagrams and a whole lot of information to help you build these circuit systems on your own.

To Sprinkle Or not to Sprinkle
for today, I will focus on the plants in my compound. I want to be able to automatically water the lawn, plants around the compound at preset times every single day of the year without much manual intervention. Yes one can easily buy a working water sprinkler off the shelve in any hardware store. but there is no fun in that. Plus, we can build a smarter system that takes cognizance of the weather to decided if it should give the plants their usual dose of water, or not water at all if it has rained in the last 24 hours. We could also throw on a Big Bank effect that brings in the watering sequence to a crescendo as part of the Christmas Lighting experience.

Examples of making of the Project Circuit Boards PCB abound on the internet. 1. Transfer a circuit trace from a Laser Printer to a paper and unto a PCB board. and 2. Rule traces manually by hand. 3. etch in an acid bath and 4. Solder on the components. etc.

Feel free to look them up and choose which one to use. For the 1st step - there are basically only two methods open to you, One, to carefully draw it with your hand using a permanent maker like a fine point sharpie, or two, to use a purpose built application to design the circuit and print it out using a Laser printer (not a bubble jet ink based printer). I have written an article on how to make a a PCB using the manual process. If you don't want to use that method, I will explain here how to follow another more precise method.

Laser Heat Transfer Method
If you desire a more professional end product, you can create professional PCB files using purpose built applications - there are a lot of applications that take away the stress of sweaty and shaky hands to deliver crisp looking products. See a list of the top 9 free PCB softwares. I have tried my hands on a couple of these, they all have their pros and cons, but I especially like Fritzing software. Its intuitive features allow you  make professional looking double sided PCB. Below is the image of the PCB I designed for the water Sprinkler. Along with its Gerber files if you wish to print it out and transfer it to the board.

Here are the Gerber files from my Fritzing design, for the sprinkler system.

After the traces have been printed on paper, they are ironed with high heat to melt the Laser Toner onto the board. As you may have noticed, this design was done on two sides - two sided boards are very difficult to make, the main problem is ensuring that the vias (the points where current passes from one side to the other side of the board. If the vias are not precisely placed, the PCB will not work.

Note: To esure that the vias line up, I utilize a light box to ensure that both sides of the mirrored print out match. I tape it on three sides before sliding in the measured fresh PCB. This way, when the PCB is etched and the holes are drilled, each trace matches. If the VIAS don't match point to point, all the vias will fail and your two sided board will fail.

After both sides are held in place, I iron both sides with a pressing iron until I can clearly see all the traces melted onto the board - most websites tell you to do this for about 5 mins, but I iron mine for longer periods than that. At the end you can clearly see that the traces have melted unto the PCB.

After allowing the PCB to cool down, I leave it in a bowl of water to soften the paper. softly rob off paper to reveal a perfect work of art...

Gloves On!!!
Handling or even inhaling chemicals is very dangerous. Please be careful with the following steps.

Choosing the etchant is very important. Boric chloride, off the shelve etchants, etc. are easily obtained in the west, but in the south, its not easy to come by. but not to worry, finding a chemical that corrodes copper is not very difficult. I use Hydrochloric Acid (easily obtained from any swimming pool shed) and Hydrogen Peroxide (From any pharmacy). One part peroxide, and two parts Hydrochloric Acid.

Please note that you should not dispose of the etchant in the drain - it could potentially corrode the pipes and sink. do not also throw it out indiscriminately as it could kill plants and pollute the earth. I use mine to clean concrete of moss. and water it down afterwards.


By now the PCB is looking very good. but we need to mark the points to drill each hole. I use a carbide score to nick the points for my pilot holes. these points are important to ensure the drill doesn't "runaway" and end up in the wrong place. scoring the PCB, only to make a dent, not to make a hole. Remember each via on the topside must match its corresponding via on the bottom. After the scoring, its time to drill the holes.