Solar Angel

What's this?

A controller for a solar heated swimming pool.

The plan

• temperature sensors
  • air
  • pool water
  • solar module
• relays
  • filter pump
  • solar pump
• displays
  • 4x7segment: air temperature
  • 4x7segment: water temperature
  • graphic 128x64 LCD: temperature graphs
  • two LED to indicate relay states
• interface
  • serial, to log data with a PC: ("airtemp:watertemp:solartemp:filterstate:solarstate")
• usage
  • 2 buttons for LCD mode
  • 1 button for "filtertime += 1 hour", hold pressed to reset filter time
  • hold displaymode-button pressed to manually switch the solar pump on or off
  • thermometer addresses, hystersis values, maximum temperature etc. hard coded in source
  • jumper for usage with 1 or 2 pumps, so the filter pump can do the solar job as long as we don''t have a dedicated pump

LCD modes

Button 1 steps through modes, button 2 steps through sub-modes.

• air temperature
  • 1px / 10 seconds
  • 1px / 1 minute
  • 1px / 10 minutes
  • 1px / 1 hour
• water temperature
  • 1px / 10 seconds
  • 1px / 1 minute
  • 1px / 10 minutes
  • 1px / 1 hour
• solar temperature
  • 1px / 10 seconds
  • 1px / 1 minute
  • 1px / 10 minutes
  • 1px / 1 hour
• combined temperatures
  • 1px / 10 seconds
  • 1px / 1 minute
  • 1px / 10 minutes
  • 1px / 1 hour
• statistics (max-, min-, average values)
  • 1 hour
  • 1 day
  • buffer
  • total
• current values
  • all (displayed in four sections)
  • air temperature
  • water temperature
  • solar temperature
  • remaining filter time

Keeping history

• 1 measured value takes 16 bit (two bytes)
• 100 measurements -> 200 bytes
• for three sensors -> 600 bytes
• for four solutions -> 2400 bytes

Format for historic values: uint16_t, temperature is stored in "decigrades". The leftmost 3 bits of each word have a special meaning:

|15|14|13|12|11|10|9|8|7|6|5|4|3|2|1|0| |valid value?|relay1|relay2|x|x|x|x|x|x|x|x|x|x|x|x|x|