ATtiny85 plant-care

Introduction

Mimosas are sensitive plants. If you leave them in lack of water for a week (holiday leave or just forgetting about it) you will be sorry!

There are many Arduino projects dedicated to this objective. It depends on what you want:

- Receive a warning (alarm sound, SMS, etc.) and you must go water the plant?

- The device is watering the plant, so you just visit it from time to time.

We selected the second option.

The Purpose

We provide an application of the Attiny85 to plant monitoring, with automatic watering of a single in-house plant, but for several months.

The user is informed about the general plant status, humidity and delay after the last watering.

Components

1. Attiny85 Mini USB MCU development board for Arduino (https://www.banggood.com/ATTINY85-Mini-Usb-MCU-Development-Board-For-Arduino-p-971122.html?rmmds=search&cur_warehouse=CN) price 2.23 €
2. Soil humidity sensor (https://www.banggood.com/5Pcs-Soil-Humidity-Sensor-Hygrometer-Measure-Module-For-Arduino-AVR-p-1046991.html?rmmds=search&cur_warehouse=CN) price 2.77€ / 5 pcs.
3. Pololu Mini MOSFET Slide Switch with Reverse Voltage Protection, SV (https://www.pololu.com/product/2811) price 2.93 €
4. 12V 280L/H Water Pump Mini Brushless Water Pump Submersible Motor (https://www.banggood.com/12V-280LH-Water-Pump-Mini-Brushless-Water-Pump-Submersible-Motor-p-1128835.html?rmmds=search&cur_warehouse=CN ) price 5.30€
5. A small monochrome LCD. We used the one bundled with an A-Star 32U4 Prime LV microSD with LCD (https://www.pololu.com/product/3109 )

a. LCD 1602 Adapter I2C (https://www.banggood.com/LCD1602-Adapter-I2CIICTWI-Serial-Interface-Module-Board-For-Arduino-p-1056942.html?rmmds=search&cur_warehouse=CN ) price 1.48 €

Schematic

Arduino Code

See this page for the Arduino code

User guide

Powered on, the device reads the soil moisture every 15 minutes, then goes to sleep. Now, depending on your plant habits, the watering threshold can be higher or lower. Our mimosa enjoys to be above 95%. If the moisture level drops below the threshold, the pump is powered. Again, each user should decide the time required for water to be pumped: too long can waste water, as the soil cannot absorb all the quantity. For our mimosa, 15 seconds were perfect time, including raising the water from 1m below the pot and then watering the plant.

Anyway, after 15 minutes the moisture level is read again and more water will be poured in, if necessary to go overt the threshold!

At start-up and after each watering, a counter is reset. There is no real clock involved, but counting the sleeping periods, a relatively accurate hour and days information can be displayed on the LCD.

So, on the LCD will be indicated the relative humidity and the time lapse since the last watering. An emoticon, showing the mimosa status is also available: :( , :| , :).

With a 5l bottle, a couple of months are without worries.

Power consumption:

- 26 mA for CPU, Sensor + Mosfet on + Display

- Uses 20 mA for CPU + Display (between readings)

- Uses 8 mA in deep sleep (Display on only)

Project New Contributions

This is one possible solution to care-taking of a plant in an apartment. It is autonomous for several months. Low power. Low price of components.