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Month / April 2017

How to Design a Cheap Plant Watering Sensor (Part 6)

This is the sixth part of the meta-tutorial, where I talk about designing a cheap plant watering sensor. If you did not already read the firstsecondthirdfourth and fifth part please do it now. These parts contain a lot information which lead to this point of the tutorial.

The fifth part ended with step 24, where I talked about calculating the total bill of materials. This part will focus on preproduction of a small batch of sensors to solve some final details.

Just note, I obviously do not follow these steps in a perfect sequential way. Often I start with some tasks earlier and things are running in parallel. There are various dependencies and it would make no sense to wait with some task just to follow a strict sequence. 🙂

If you follow my blog you may already read some details about ongoing tasks. I will just briefly talk about them in this article. You will find more details in the other blog posts.

Step 25: Build an Alpha Series

Everything looks very promising, so its time to build a small batch of the final devices to see if they work as expected. This is also a test to see how a larger number of these devices can be produced and what kind of tools are needed for this task.

Order the Components

First I order the components. This is very important, because the availability of electronic components changes all the time. It is nice to have all required components, so you can order the boards with the correct footprints. If you order the boards first and are unlucky, an important component is suddenly unavailable and you have lots of boards with wrong component footprints on it.

The components for the plant sensor are really cheap, so there is no huge risk. Even it turns out a huge issue requires a component change – it will be a small loss. SMD components also do not take a lot of space, I can easily store all of them in a very small box.  Continue Reading

Successful Measurements

Using the new method of measurement, described in this post, I could successfully collect some meaningful data. This time, the read values are the exact values of the final sensor without a different kind of oscillator.

I watered the plant at day zero with quite a great amount of water. From there you can see how the frequency slowly rises, while the soil in the flower pot starts to get dry. There is a small measurement error between day two and three. Here I had a short power loss and no data was recorded which resulted in some zero records. Continue Reading

Plant Watering Sensor – Long Term Tests Take #2

I started a second take on the long term tests for the plant watering sensor. This tests are required to be sure, the measurements follow the expected cycles. After watering the sensor, the frequency should go down and while the soil is drying up, the frequency should go up the the initial value. Logging this […]

Plastic Cup Meltdown – Working with Epoxy

Currently I am working on the coating for the foot part of the plant watering sensor. Here I already tried a wide range of techniques and materials. At the moment, epoxy seems the perfect material choice – so I am trying different resins and hardeners to get the best results. Some hardeners are very reactive […]