This repository contains circuit diagram and code for low power chicken door using ESP-8266 (ESP-12) microcontroller, DS3231 RTC module and 28BYJ-48 stepper motor.
Purpose of this project is to create a chicken door that will automatically open in the given time in the morning and close in the given time in the evening.
Besides this automatic procedures, manual operation is also allowed using external button to open or close gate whenever needed.
Configuration and time setting is possible via long pressing the external button - that
will start a WiFi access point with captive portal, so once user connects to the
chicken-gate WiFi, he is redirected to the settings page, where it is possible to
synchronize time or set a different timer for opening/closing the gate.
- Board: Generic ESP8266 Module
- Upload speed: 115200
- Flash size: 4M (1M SPIFFS)
DS3231 is a great real time clock chip, but the standard module drains too much power for use in low power device running on battery. Fortunately it is possible to lower the power consumption to just a few micro amps when making a few small adjustments described in this video.
Namely, I made these adjustments:
- removed the 1k resistor to disable the power indicator LED
- bypassed the 200 ohm resistor from the "battery charging" circuit
- cut the trace from the + terminal of the battery to the VBAT pin of the chip
- added a 1N4148 diode from the + terminal of the battery to the VBAT pin of the chip
- added 1uF and 0.1uF decoupling capacitors between VBAT and GND
- lift up (or cut) the VCC pin of the DS3231 so that it doesn't connect to the board
This is how the board looks after the mods:
Library I used to communicate with the module is available here
I was able to lower the power consumption of ESP-8266 board by using the deep sleep mode. The board is woken up by an RTC module or by an external signal, so no circuit is in place (GPIO16 connection to RST pin) for ESP to be able to wake up itself.
Current draw of the board and supplemental circuit in the deep sleep mode is about 27 uA (~0.03 mA) and approximately 700 mA when opening/closing the gate (while stepper motor is responsible for most of it). One operation cycle (closing, opening) takes in my case 34 seconds.
It means that in theory two operation cycles per day will drain 13.3 mAh while sleeping for the rest of the day will drain additional 0.72 mAh. One standard day will therefore need around 14 mAh.
It means that one 18650 battery with capacity of 1800 mAh should power the device for around 128 days, i.e. over 4 months.
Standard 28BYJ-48 stepper motor is working in a unipolar mode. It is possible to increase the motor torque using the bipolar mode, but it is necessary to adjust the motor in a way described for instance in this guide.
I followed these instructions and adjusted the stepper motor to increase its power to lift up the gate.
To see the video of working device, check out the video on YouTube.