Sabah Zdanowska - Creativity in Design Blog

Making for Designing. The Arduino Soil Moisture Sensor

I chose to build an Arduino soil moisture sensor for plants. This was part of my team's immersion exercise, focusing how people grow things in small spaces, how can we take care of plants when we’re not around and how can smart technology help us to maintain our plants?

I also wanted to use the soil moisture sensor as a physical prompt to engage with people. Connecting things, sensing, measuring and alerting are key concepts behind the smart city idea, so I thought this kind of probe would be ideal for eliciting feedback from people in the city about the smart city. Specifically I wanted to find out whether the idea of a soil moisture sensor fit with people's perceptions of sustainability and empowerment and what they understood these words to mean when it came to the smart city. Additionally, I wanted to find out if people linked the idea of the smart city with nature.

Building the Arduino Soil Moisture Sensor

I managed to borrow and Arduino kit from a classmate and looked up different designs for the soil moisture sensor on the internet. The Arduino kit included most items, but needed to buy the moisture sensor. I bought a pack of three on eBay as I wanted to try to use one Arduino for multiple moisture sensors as people are likely to have multiple plant pots in one home. Luckily I was able to find a tutorial on YouTube that would help me to achieve just that.

The soil moisture sensor

Red bulb = please water, Green bulb = soil moisture is good

The video tutorial could make it difficult to see what was happening so I decided to draw a diagram (left) using the online opensource tool called Fritzing to make it clear to me. I then annotated the diagram in Paint to document my process.

Essentially, I would have two sensors in 'parallel', so that they would independently of one another. The red and green light bulbs for each of the sensors would be in series so that depending on the reading from the sensors only one of the bulbs (either red or green) would flash.

Green would mean there is enough moisture in the sensor
Red would mean that the plant is in need of watering

Once my moisture sensors had arrived, I built the circuit and uploaded the code to the Arduino program.

Barring a few hiccups I was able to get the circuit working fairly easily.

The code in production and a flashing red light!

Sensors plugged into two of my plants at home

Getting Feedback from City Dwellers

Ideally I wanted participants to handle and try out the soil moisture sensor for themselves, so that I could observe how they interacted with it. I was also planning on asking participants to take photographs of how and where they might use the soil moisture as a cultural probe exercise.

Unfortunately, due to the need for social distancing, I had to rely on feedback from friends and family for feedback via video calls. I managed to demonstrate the soil moisture sensor using a couple of my own plant pots and had a one to one discussion with three people, hoping that it would prompt them to talk and ask questions, which I could them build upon to speak to them about the smart city.

I asked all three people I spoke to to draw a facial expression on a piece of paper.

These are copies of the drawings from Person 1, 2 and 3 from left to right as I did not have permission to use the screen recording.

I then had a follow up conversation, which I kept it fairly unstructured. Broadly, I tried to elicit feedback on the following:

What made them draw their expression
Did they think it it would make us as society more sustainable
Did they feel like technology such as the homemade soil moisture sensor would empower them
Did they connect the idea with the smart city

I transcribed relevant bits here:

Person 1, male, early 30s:

"I've always wanted to buy an Arduino... I'm not really into plants, but I do like DIY, it's quite cool to make something like this. I thought the smart city was about 5G and having everything connected, so yeah I guess plants could be connected too. The sensors should be quite cheap so you could have millions of these around the city and make sure everything is automatically watered."

Person 2, female, late 60s:

"I think this would be quite helpful, although I do have a lot of plants, so don't know how I would track everything. I already have a small LED planter for my herbs, so I think I could buy something like this if it wasn't too expensive. I wouldn't make anything myself. I think it's helpful as it's hard to keep track of what needs watering... sometimes my husband waters the plants and I don't realise. I don't really know what the smart city is, I've heard the term, but I'm not sure what is means."

Person 3, female, mid 40s:

"I don't know how I feel about this. I have some pot plants on my balcony, but I buy easy to look after ones... I'm just not keen on making nature super-techy and as for sustainability we need something on a much bigger scale, although I can see how this can make people feel like they can do something about it, but honestly people can't even clear our their lofts for free insulation! I haven't looked into the smart city that much, but I thought that would be something on a bigger scale, like for the whole city. I didn't think it had anything to do with plants!"

When analysing the feedback, I noticed three important things:

The probe appeared to help all three people make the connection with the smart city, however, the idea that plants had anything to do with the smart city was new to them.
Beyond the 'everything connected' idea, none of the people knew what the smart city really was, if it had anything to do with sustainability or that being 'smart' could be down to the individual. It was what someone, somewhere else was making decisions about. Given that one of the values we had as a group for our project was empowerment, I thought there was work to do here.
Nature and technology did not have to be separate according to Person 1 and 2. Only Person 3 was opposed to this idea. This made me think about how technology is designed when it comes to the natural environment is important to consider and perhaps we should try harder to make sure it's not intrusive when people are looking to nature as a place to switch off.

Reflecting on the use of a Probe

I thought that the exercise was fairly successful. I was able to use a physical prompt to engage with people on a topic that clearly none of them had given much thought to. It helped me to engage them in a discussion about the smart city and elicit a meaningful response. I don't think I would have got the same answers if I had carried out a survey by itself, as even the answer "I don't know" was insightful. I got more feedback on why a participant didn't know or why they had not thought about something, which was insightful in itself.

Even just the process of building the soil moisture sensor and becoming familiar with the Arduino kit myself was valuable. It enabled me to think about how these small sensors and quite simple technology could permeate an entire city. There could be millions upon millions of small sensors deployed in the city on a massive scale. How would I feel about that?

Building the moisture sensor myself was rather exciting. I quite literally jumped for joy the first time the bulb lit up and I realised it worked! It is hard to figure out how this feeling would translate to millions of sensors across a city. Would I still feel excited, now that I've experienced building one harmless little sensor? Maybe just a little...

In our group discussions, we agreed that use the use of sensors on buses or for smart lighting we were comfortable with, but collecting data on humans was completely different. I'm not frightened of the technology, but I am wary of how humans will use it, especially when it comes to collecting data on other humans. Here, I do not trust that everything will be alright.

I expected that using a physical probe to prompt and stimulate others would help and guide myself and my group towards designing something related to the smart city. What I did not expect is that in the act of probing others, I was also probing myself.

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