Aquarium

Automised aquarium with STM32

Description of the project:

Automated aquarium with the following features:

• temperature measurement
• maintaining given temperature
• feeding
• controls over WiFi
• Automatic failure detection and shut down

Required elements

1. STM32F4
2. Display Nokia 5110
3. Programmable Resolution 1-Wire Digital Thermometer DS18B20
4. 2 Relay Modules
5. Resistor 5W5.1ΩJ
6. 4x4 Matrix Membrane Keypad
7. SERVO MOTOR SG90
8. ESP-12F WiFi Module
9. attiny85
10. NTC 100K thermoresistor

Failure detection with AT tiny 85

The Code is located in /tiny_guard/tiny_guard.ino file. It uses the analog pin to measure the temperature with a 100K thermoresistor. The thermoresistor is connected to 5v together with another 100K resistor. The voltage is then measured on AT-TINY's A1 pin. It could be then converted to current resistance of thermoresistor and then to current temperature as shown in this guide.

But at-tiny doesn't have enough memory to perform these operations. Thus, it can just measure the voltage and compare it with the critical voltage, for which the temperature is too high.
If the temperature (or corresponding to it voltage) is too high, at-tiny stops supporting the STM32 with voltage.
To convert from current voltage to temperature and vice versa, we wrote the script temperature. on JS. One can just run it in browser, open console with F12 and use functions convertAnalogIntoT() and convertTtoAnalogIn() to switch between at-tiny voltage measurements and temperature.

The pin 0 is used to switch the voltage to STM. It is connected to a relay. Because we connected the relay to inverse input, it will provide voltage when OUPUT = 0 and stop it when it is the maximum value of 255.

Note that at-tiny analog in output is between 0 to 1023 (corresponding to voltage from 0 to 5v accordingly). The analog out (PWM) needs to be between 0 to 255 (0 to 5v as before).

Connection to server with Node MCU (ESP 8266)

To control the aquarium over the internet, the following was configured:

1. Server to receive and transmit data to both user and aquarium itself.
2. Node MCU module to receive data from STM using UART and transmit it to server.
3. STM 32 to transmit data to Node MCU and process received data correspondingly.
4. Website to send data to server about aquarium controls

Server

Server needs to do the following:

• Receive and save current temperature measurement in the aquarium.
• Save the required temperature. Change the required temperature if either user changes it on website or aquarium manual controls. Send the current required temperature to aquarium (especially if the aquarium restarts - to reset previous configurations)
• Show user if aquarium is currently heating or not
• Get command to feed the fish from user. Display to user when the command is awaiting to be performed and when finished (on UI button is disabled and enabled back correspondingly).

Server code is written on Python and hosted on pythonanywhere.com. Files are in UquariumServer.

Node MCU

The code is located at esp_8266_wifi/. The commands that it was programmed to receive using UART at BaudRate 9600 are:

• Get available wifi connections (list of wifi uuids)
• Connect to wifi
• Check whether it is currently connected to wifi
• Disconnect
• Configure request to server
• Send request and get response
• Echo

Most commands ouput if they were successful or not. Also some functions are split into 2 parts. For example sending something over the internet takes some time. So there are 2 commands:

• To send the data to a url.
• To check whether the response is ready and receive response.
  The UART communication is then managed by STM and it never needs to wait for response from Node MCU, just check whether there is data to transmit from Node MCU when STM is ready to receive.

The entire list and usage of commands:

COMMAND	DESCRIPTION	ARGUMENTS	RESULT
READ NETWORKS	Ask Node MCU to get a list of available wifi networks and store it inside its memory		T/F - already in process
GET NETWORKS	Send the list of networks retrieved in previous command		T/F - list ready, list itself
WIFI CONNECT	Connect to wifi	wifi uuid and password
IS CONNECTED	Is already connected to wifi		T/F
DISCONNECT	Force disconnect from wifi
CONFIGURE_REQUEST	Configure the next requests to be sent	POST / GET request, url	T/F - successful
GET CONFIGURATION	Get current request configuration (to test if everything is ok)	T/F - configuration exists, configuration
SEND_REQUEST	Send request	request body	T/F - successfully started
GET_RESPONSE	Get respose		T/F - response for last request received, response body
GET_RESPONSE_CODE	Get the status code of last response		F if none, code otherwise
ECHO			The ECHO command code itself

All the communication via UART is performed using interrupts, so Node MCU can perform an operation and communicate with master simultaneously.

STM

The corresponding communication code of STM is in wifi_node_mcu (code, header) It has the code to perform operations, used in our project. Also, STM has functions to process data from server, change its configurations accordingly and send current status back to server.

Website

Microcontroller pin configuration

General configuration of pins:

Display:

For dislpay we need 8 pins, we connect it as follows: RST - PB10, CE - PB14, DC - PB12, DIN - PB15, CLK -PB13, VCC - 5V, BL - PB7, GND - Ground. The functions for display is in aq_interface.c

DS18B20 Thermometer:

For thermometer we need 3 pins. Thermometer uses OneWire interface for communication using external library. Functions to work with it are in aq_controller.c.

To address the thermometer we use the SKIP ROM [CCh] command (Which addresses all one wire slaves on the line. In our case there is only one - thermometer, so we address just it. But one can also use its ROM code for this).

After that we send the Convert T [44h] command to order the thermometer to perform its measurements and convert to required output. If we start reading, the thermometer will transmit 0 until the operation finishes.

The Read Sketchpad [BEh] is used to get the measured data from thermometer. The temperature is send in the first 2 bytes, lower bit first. The measurement needs to be further divided by 16, because its 4 least significant bits are after the floating point. The error of measurement is ±0.5 °C.

Relay and resistor

We first wanted to connect the heating resistor, using a darlington transistor array:

But it didn't prove to be worthful for such high voltage, so we needed to use a Relay instead.
The Relay is connected to PB7 pin, as on image. The pin is connected to Relay's signal input. The resistor is connected serially to relays NO and COM. This all is connected to 12V. With such configuration the resistor is off when STM has no voltage or outputs HIGH. It has voltage and is heating if STM outputs LOW.

Functions for maintaining of temperature is in aq_controller.c.

Keyboard:

The keyboard has 4 inputs and 4 outputs. If a button is pressed, voltage is able to flow through one pair of the outputs and inputs. But because one cannot determine which exact button is pressed if all the inputs are HIGH, we needed to turn the inputs one by one and measure the outputs also one by one to determine which exact pair is connected - and so determine which button was pressed.
Because most of the time keyboard is not pressed, the code checks for which button is pressed only after an interrupt from the input pins is received (Of course, the voltage should be HIGH at keyboard inputs at this time. Otherwise we wouldn't get the interrupt).
Also the input needs to be pulled, so that we can always read meaningful information from keybaord.

Connection:

From left to right first four for output - PD8-PD11, next four for input - PD0-PD3 (configured for interrupt).

The code for keyboard is in keyboard.c.

SERVO MOTOR SG90

For working with SERVO MOTOR SG90 we need 3 pins, PB8 for output, Vcc and Ground.
Servo receives PWM signal and rotates correspondingly to the duty cycle of it. (-90deg to 90deg corresponding to cycle of 1ms to 2ms) The period is 20ms.

The code for it is in aq_dispancer.c.

Photo