Design - 12V DC Backup Power auto switcher for Solar Powered backup system
Use - I am using this to keep continuous power to important devices in case of power outage.
Example Devices: Smoke Detectors, Security System, Network Router, Network Server / Switches, and home automation control center
(Note: all of these run on 12V, or run on a voltage that I am going to adapt from 12V such as 9V)
I have settled on my final design for this device. I chose the design for it's simplicity, affordability, safety, and functionality. I ordered the parts which cost me less than $30 before tax and shipping costs. I will include a parts list and schematic.
Input #1: 12V DC from Solar powered battery backup system
Input #2: 12V DC from a 110VAC to 12VDC Power Adapter (Suggest 5A Current Rating)
Output: 12V DC (5A Max) - Supplied from AC when available, automatically switched to solar powered backup battery source without interruption in case of power outage.
A Green LED will light to indicate the unit is powered by the 12VDC from the AC Adapter.
A RED LED will light to indicate the unit has switched to and is being powered by the 12V DC Backup System
Relay: Relay1 = Z988-ND - 12V Relay 8A SPDT NC
Power Diode: D1, D1 = 6A2-TPMSCT-ND - 6A 200V Rectifier Diode (To provide isolation)
LED Indicator: D3 (Red) = 67-1067-ND - Red 12V LED 3MM
LED Indicator: D4 (Green) = 67-1061-ND - Green 12V LED 3MM
Capacitor: C1 = P5142-ND - 16V 1000uF Radial
Power Connectors: (Optional) CP-011B-ND - 5.5/2.5mm O/ID DC Power Jack Panel Mount
Power Cable Ends: (Optional) CP-2184-ND - 5.5/2.5mm O/ID DC Power Cable End
Parts available from: www.Digikey.com