Solar Shed - New Design

 

In my last update, I stated the need to redesign this.  I went through the extra parts I have and started working on a new design that eliminated the Curiosity HPC development board.  Here are the changes that have been made.

1. Had quite a few PIC18F4525 PIC processors.  Since they had 48K of FLASH memory, that made them a good choice.  The FONT files for the OLED take up to 64K, but they can be trimmed downed to fit in 32K, so this will work just fine.
2. Changed the LED configuration a little and with a custom PCB I can label them and make them different colors so I can easily tell what is happening.
3. I added a DC-DC converter circuit that will take either the Solar Panel output or the Battery as input and make 5VDC.  This is the same DC-DC that I used in the Train Light Controller.  I had to buy 20 of them from the Asian after market, so these are essentially free.  
4. I changed the way the relays work.  While this is hard to read, it is good enough to explain the basics.  The top relay works as before connecting/disconnecting the battery from charging.  The middle relay connects/disconnects the LED lights in the shed.  The bottom relay is new and allows for either the battery or the solar panel to provide power to the DC-DC converter that then powers the PIC circuit.  Also the relays are now powered either by the battery or the solar panel through the LT1085 in a wired OR configuration. 
   
   
   
5. Finally the PIC is still at 3.3VDC since that is the power of the OLED display.  To provide a quasi battery backup, a large super capacitor (7.5F) is installed between the DC-DC output and the 3,3VDC LDO input.  When the solar panel goes under voltage and the battery is also under voltage, the super cap should power the PIC.  It will be sleeping 90% of the time, waking up every few minutes to check the voltage on the solar panel and the battery, if neither is sufficient it will go back to sleep.
   
   
   
6. Added two push buttons that will allow me to manually change the relay that charges the battery and the relay selects the power source for the DC-DC converter.  This way if I can make sure the battery is connected/disconnected and the appropriate power source is selected. 
7. I added four #6-32 holes to make mounting easier.
   

Need to some final checks, then I can generate the PCB files.  I am working on a few other designs so that I can take advantage of combined shipping.