I have upgraded an almost 50 year old map of Paris to display solar/lunar positions.
Since I could not find a (free) web service to query solar and lunar azimuth and elevation, I used equations from Meeus, Jean. Astronomical Algorithms, 1998 and Astronomy Answers to do the calculations myself. The accuracy is very poor and there are probably bugs.
The lack of double precision of the ESP8266 means that basic astronomical calculations cannot be performed with the necessary precision. For example, the Julian day number (JDN) cannot actually be calculated to the day. I have currently hotfixed this specific problem by breaking the equation into integer and floating point parts, but all following equations lack accuracy and in the long run I will just upgrade to an ESP32.
Next to the solar/lunar map I have added modes to display the current time in the style of an analog clock style and some random animations as well as static ambient lighting.
The map can be controlled from your home wifi through a web interface that has its own repository.
The worst case consumption of the 180 NeoPixels I used for this project is
4 LEDs (RGBW) x 0.02 A (max current per LED) x 180 NeoPixels = 14.4 A
The ESP8266 consumes up to 250 mA. So the worst case estimate amounts to 14.65 A, which will never be reached in practice. Nevertheless, I opted for the next larger power supply (15 A) because it will run cooler as it will never reach its limit and excessive heat could damage the map or dissolve the glue.
So this 15A/5V power supply should be more than enough
- 1000 uF capacitor connecting the + and - terminals of the power supply to prevent initial current peaks from damaging other parts of the circuit
- 340 Ohm data line resistor close to the first NeoPixel to help prevent voltage spikes damaging it (see the Adafruit NeoPixel Überguide, they recommend 300 to 500 Ohm)
- 74AHCT125N level-shifter from 3 V board logic to 5 V NeoPixel data signal
- 15 A Fuse and a Fuse Holder
Of course some cables are required. I soldered the microcontroller and the level-shifter on a prototyping board.
Create a file named connection that contains one line ssid:passwd. This later enables the project to access the internet in order to retrieve date and time for the solar/lunar position calculations and the clock visualization.
Variables in frame.py that need to be adjusted according to your frame.
The number of LEDs
n = 180
The number of horizontal (cols) and vertical LEDs (rows)
cols = 54
rows = 36
The number of LEDs per centimeter
leds_per_cm = 0.6
Latitude and longitude of the location in degrees
coords = (48.860536, 2.332237)
Download the latest stable ESP8266 MicroPython firmware and create a new Python environment if not done yet:
conda create -n esp python=3.8.3
conda activate esp
pip install esptool
Connect an USB RS232 adapter to the HUZZAH ESP8266:
| |
| ( ) (TX) (RX) (C+) ( ) (GND) |
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Clear and flash firmware (press/release RESET while holding GPIO0 button to put it into firmware flashing mode)
python -m esptool --port /dev/tty.usbserial-XXXXXXXX erase_flash
python -m esptool --port /dev/tty.usbserial-XXXXXXXX --baud 460800 write_flash --flash_size=detect 0 esp8266-20220618-v1.19.1.bin
Keep the USB connection for the next step.
Open emulated terminal and initiate the setup process while still being connected to the USB RS232 adapter:
screen /dev/tty.usbserial-XXXXXXXX 115200
import webrepl_setup
Follow setup steps and restart.
I ran into size issues at some point which could be solved by pre-compiling the scripts into bytecode before transferring them to the ESP8266.
In order to do so, clone the MicroPython repository.
git clone https://github.com/micropython/micropython
You should checkout the version according to the firmware you just flashed.
make -C mpy-cross
Compile all modules except for the main module:
/path/to/mpy-cross/mpy-cross module.py
Clone WebREPL to have an offline version or use the cached online version:
Connect to the MicroPython-XXXXXX WiFi network using the password set or default password micropythoN.
Transfer main.py and compiled modules as well as the connection file to ESP8266 using WebREPL.