sunrise - sunset calculator

These scripts can calculate sunrise + sunset time for specific location and date.

motivation

Activate a staircase LED light just before sunset to save the energy, but make sure the staircase is well lit for safety reasons. The staircase LED bars are controlled by WiFi Smart Socket [ Kankun / Konke ] running OpenRWT. So any similar smart-plug device based on OpenWRT should work ...

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possible solutions

Simplified overview of possible ways to approach the problem with pros and cons:

• online services (sunrise/sunset calculators)

  • pros:
    • very easy implementation
  • cons:
    • does not work off-line
    • unreliale in long run as public free services tend to be sold, change their interfaces etc ... simply speaking if they cannot make any profit from you (pushing ads) they do not like you and make everything in their power to block you from using their precious service

• precalculated lookup table

  • pros:
    • easy implementation
    • works off-line
  • cons:
    • limited flexibility (table has to be recalculated for any new location)
    • requires support tools for table calculation

• real-time sunsrise/sunset calculator

  • pros:
    • works off-line
  • cons:
    • not easy implementation

• dark/dusk sensitive input:

  • pros:
    • location independent
    • can handle also special cases like sun eclipse, heavy clouds during the day
  • cons:
    • requires hw modification (add photosensitive LDR element)
    • requires fw extension (OpenWRT package to setup sensitivity etc)

This is the implementation of "real-time sunrise/sunset calculator"

implementation

Implementation is based on R code [ sun.info.R ]. This R implementation looks very precise (within a few minutes) while complexity of the code is not high. Even the comments and variable names are matching as close as possible the R-code for easy cross-references.

scripts

The repository contains following scripts:

• sunrise-sunset.py ... python implmenetation as a proof-of-concept (PoC) to verify the functionality

• sunrise-sunset.awk ... awk implementation for OpenWRT

• cron-sunset.sh ... cron wrapper for OpenWRT

• relay.cgi ... cgi/cli scripy to control Smart Socket relay

sunrise-sunset.py

Python implementation - just PoC as python in not included in OpenWRT [ Kankun / Konke ] customized firmware.

sunrise-sunset.awk

AWK impelementation - suits pefectly for OpenWRT [ Kankun / Konke ] customized firmware as awk is build in. A few math/system functions have to defined explicitly as they are not part of awk, like absolute-value, arcus-cosine, convert degree-to-radians and sleep. The rest is just command line parameter handling, verbose output and some conversions for human friendly format.

There are four mandatory cli parametres: latitude, longitude, mode (sunrise/sunset) and offset.

Executing with less than four parameters shows this usage help:

= calculate sunset/sunrise time for location and date = awk script for OpenWRT = ver 2020.05.01 =

usage: sunrise-sunset.awk [-v v=1] -- latitude longitude [sun]set|[sun]rise offset [dec|hms|systime|sleep] [yyyy-mm-dd]

-v v=1     ... optional verbose output
latitude   ... location lat.  coordinate [decimal]
longitude  ... location long. coordinate [decimal]
[sun]rise  ... calculate sunrise
[sun]set   ... calculate sunset
offset     ... offset in minutes (negave = before, positive = after)
dec        ... print decimal value of sunset/sunrise [hours]
hms        ... print human readable h-m-s value of sunset/sunrise [h m s]
systime    ... print unix time value of sunset/sunrise [sec]
sleep      ... sleep till sunset/sunrise shitfed by offset value
yyyy-mm-dd ... use this date for calculation (default today)

multiple parts can be requested to return, e.g:  -- lat long sunset offset 'dec hms systime sleep'

The basic usage scenario is either:

• to schedule the job to run at time calculated by sunrise-sunset.awk
• to let the sunrise-sunset.awk sleep and execute the job after the sunrise-sunset.awk call

cron-sunset.sh

Intended to be called directly from cron. It is just simple wrapper for sunrise-sunset.awk providing parameters and logging. The wrapper is executed by cron at the scheduled time. Then it sleeps until sunset - offset time. When sleep is over configurable action is executed (switch on the lights). If execution (cron) time t is after the sunset then action is executed immediately. So for example the cron is executing wrapper cron-sunset.sh at 17:00. That means the light will switch on no sooner than 17:00 or at sunset - offset time. The offset is for fine-tune adjustment. Optional action logging logs via standard logger. The script accepts action paameters (default to "relay.cgi on").

relay.cgi

Simple script to control [ Kankun / Konke ] relay. Can ba called either from command line (cron job) or via http cgi extension.

Accepted parameters are:

• toggle ... just toggle the current state of relay (off -> on, on -> off)
• on ... activate relay
• off ... deactivate relay
• status ... return status (either on or off)
• anything else (even no parameters) is handled as "status" request

Command line (CLI) parameters examples:

# /www/cgi-bin/relay.cgi on
Content-Type: text/plain

ON
# /www/cgi-bin/relay.cgi status
Content-Type: text/plain

RELAY is ON

http request (CGI) parameters:

http://device/cgi-bin/relay.cgi&on

http://device/cgi-bin/relay.cgi&status

To do

Possible future improvements and extensions:

• optional location autodetect by ip geolocation
• additional LDR (dark/dusk sensitivity) option