An alarm clock that does not display the time, but lights itself depending on the time of the day.
An esp8266 microcontroller lights an RGB led in different colors depending whether the children must stay in their room or they are allowed to wake their parents up.
A full-on led in the dead of the night is a sure way for kids to not go back to sleep if they ever wake up. To avoid this, a photoresistor is used to sense ambient light and adjust luminosity accordingly.
The setup uses an RTC clock with backup battery to help keep time reliably. Daylight saving is taken into account.
The clock uses 3 parameters:
- sleep time: time at which children must go to bed. Led becomes blue,
- wake-up times: times at which children may leve their room at wake their parents up. One for week days, and another one for weekends (one can dream of a Sunday sleep in). Led goes orange for 2 hours.
To update these times, the clock offers a web interface. It's not connected to home wifi for various reasons but instead creates its own SSID when you need it.
When you press the button, the clock creates its own SSID. You must connect to network Hérisson (public, no authentication). Ease of use trumps everything in such a simple, low-risk project. SSL and auth (WPA2-PSK) are not worth the hassle, both for dev and use. Wifi is off most of the time anyway.
Go to http://192.168.14.1 to access the web interface. There, you can edit any of the times (sleep time, wake-up times for weekdays and weekends) as well as the current time and date. Web ui is a single html file uploaded to esp8266's internal file system (SPIFFS).
The led blinks green when wifi is on. Just press the button again to switch it off.
Why not having it connected permanently?
- home wifi is flaky in the room,
- very sporadic usage does not need 100% connection,
- lower power usage when modem is off
esp8266 has 4k EEPROM. We use it to store the alarms (4 bytes each) and daylight saving flag (1 if winter time has been done, LSB bit in first byte of the memory bank). Alarm times are stored in minutes since 00:00.
Address | value | Desc
--------|----------|------
00h | 00000001 | winter time change done
01h-04h | | sleep time
05h-08h | | weekdays wakeup time
09h-12h | | weekend wakeup time
- Day of week (dow): 1: Monday, 2: Tuesday, (...), 7: Sunday
Light output is proportional to ambiant light. The relation is not the simple identity function f(x) = x.
To create the ideal function, we want to plot values.
The sketch calibrage creates a web server (public SSID Hérisson, 192.168.14.1) with endpoints:
GET /senseto retrieve ambiant light value (theoretically 0-1024),POST /led?r=R&g=G&b=Bto set led output ; R, G and B being the PWM values for each channel.
We try to find the ideal output in each color (sleep blue and wakeup orange) for multiple ambiant light values. Results are in resultats_calibrage.ods file.
For each channel, we want to write a function that more or less reflects the calibration data points. The ideal function should be superimposed over the data points if plotted along them. We do that by considering that the values between 2 data points should observe an affine function (with data range extremities being minimum & maximum values).
tests/pwm_function/pwm_function.cpp implements the affine functions and compares with calibration data to verify that's ok ; and herisson/lightModulator.ino simply copies this code, with a few last-minute adjustments.
-
DS3231 handles leap years correctly.
-
Daylight saving time change is checked and performed on sunday in the last 7 days of march and october. Update time and set winter time flag in eeprom.
-
To upload a sketch onto the ESP8266, it must in bootload mode. The procedure is as follow:
- Hold down the GPIO0 button, the red LED will be lit
- While holding down GPIO0, click the RESET button
- Release RESET, then release GPIO0
- When you release the RESET button, the red LED will be lit dimly, this means it's ready to bootload