Flotcher = Flower + Watcher

I hope that makes sense, but I am afraid it's not ;)

Welcome in this instructable, here I will show you how you can make your own flower monitor that will inform you when your flower will need water. That's quite important for me because I am making stuff all the time and I always forgot to water my flowers. There is some soldering in this intractable and basics electronics, but we wouldn't use any microcontroller, this project is based on resistors and transistors, no programming required.

This project shouldn't take more than an hour to make, it's rather simple and quick one.

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Are you ready? Let's start!!!

Step 1: Why?

Why flower monitor? As I said my flowers are not in good condition because I always forgot to water them. Annoying sound of buzzer at 3 AM is perfect way to make me water them :) that's the best way to keep them alive. That's the first step to automate my house. I mean this kind of device is not an automation, there should be some kind of pump to water flowers automatically but then I should remember to put water in the pump tank...

I will work on that in the future :D

You may be also curious why I made it with analog electronics and not microcontroller. I like challenges and creating things that I cannot do is for me the best way to learn how stuff works. If it good for me it maybe good for you! So if you want to learn something, this project is perfect for you :)

About some more technical things. Transistors are cheaper than microcontroller, you don't have to program it, so you don't need to have a programmer, it's less complicated and smaller, smaller battery consumption (? I am not exactly sure about the last one, but I hope it's true).

So that's all for why? now let's move to how?

Step 2: What You Will Need?

We don't need a lot for this project, 8 components to solder to the PCB and PCB itself. You should buy this components for about $1, you can buy PCB from me on Tindie. Here is everything that we will need:

Buzzer with generator (5V or 3V)
BC847 SMD transistor (3 of them)
1MΩ resistor (2 of them in 1206 package)
47kΩ resistor (1206 package)
10kΩ potentiometer

You don't need cent for this project it is just for reference how small those components are :)

Step 3: PCB

PCB for this project is very tiny, and it's blue! I like blue. As you can see moisture sensor is integrated in the PCB so you don't need any external stuff and project is really compact. I tried to make it as small as possible but also big enough to make it easy t solder components on it. If don't have any experience with soldering don't worry there are just few components so it's perfect to practice a little bit. You can find above all of the files for PCB in case you want to change something or just take a look. There is also .zip file with everything you will need to manufacture this PCB. Here is link if you want to buy this PCB from me:

Step 4: How Does It Work?

Moisture sensor that is placed in the ground of your flower measures resistance of the ground (more wet ground = smaller the resistance, more dry ground = bigger resistance). Because we want buzzer to turn on when flower is dry I used a not gate (see transistor Q1) you can find on the Internet a lot of explanations on how not gate works, they are much better than my explanation is :) Next 2 transistors amplify signal from the first one. There are 2 transistor that amplify the signal because signal on the not gate is very small so that this device uses small current and can work long on a battery. You can adjust sensitivity of the device with potentiometer. When there is no current flowing through moisture sensor, output on the not gate = 1 so the buzzer is turned on thanks to transistors that amplify the signal. After watering the flower current can flow through moisture sensor so buzzer is turned off. I hope that this brief description of how it works is understandable, if you have any questions, let me know in the comments!

Step 5: Soldering

We have to solder 8 components to the PCB, let's start with smallest SMD components. At this point tweezers are very useful so that you can hold a component in place while soldering, using small solder also helps a lot. Every element is labeled on the PCB so you will do that without any problems. Here are the values of each component according to labels on the PCB:

R1 - 47kΩ
R2 - 1MΩ
R3 - 1MΩ
Q1, Q2, Q3 - BC847C

Make sure that all solders are fine and that there are no any shorts. After SMD soldering you can put in place all THT components, there are actually only two of them :)

Solder them in place, make sure that polarity of the buzzer is ok. You can find small + on the PCB that indicates where the + of the buzer should be. At the end I added a battery holder to the back of the PCB and soldered it to the power connectors.

Step 6: Some Adjustments and Improvements

The first adjustment that you can make is to set the potentiometer to proper position so that it will detects when your flower is dry. I also decided to stick battery holder to back of the PCB with double sided tape.

Step 7: How to Power It?

There are two ways to power this thing or at least two that in my opinion are the best. Standard AAA batteries, this device should work on those batteries for a really long time (more than 200 days). But even better power source is a small solar cell. Not only because this device will work infinitely with it but also will be off at night so that you can sleep :) I don't wanted to use a coin cell battery because with it this device wouldn't work for a long time.