Welcome to this page on how to build a simple USB  Emergency back up power supply for the thousands of USB devises on the market today!!!

Now if you would like to see the Emergency USB power bank working in a power cut then click here

1) Why I designed this simple USB emergency back up power Switch is down to the many thousands of USB devises on the market today things like Mobile phones, USB Security Cameras, tablets your own USB projects and so on its endless its also designed to cover all models of USB power banks too.

2) Parts List below,

1). Relay the one I used in the  Prototype was a Omron G2R-2 PCB Power Relays 5V - DC Coils - 5A DPCO  Contacts. Ebay here UK 

1). 5 mm LED Ebay click here

1). 5 mm led holder Ebay Click here

1). Project box the box I used in the prototype was Plastic Project Box Case 72 x 50 x 26mm Small will take PP3 With lugs 35g 751 | eBay UK

1). Five volt USB Power bank any type will work fine ebay  but some may need adapters. 

 2), USB 2,0 Extension cable A Male to A Female High Speed Lead Ebay Click here.


Now we will start the construction cut the USB cable to the length you want them starting with the input USB lead first cut the wire again so you see the inner wires of the USB cable look for the RED and Black wires and cut the other wires as we don't need them. 

Now connect them up as shown in the schematic diagram above this will be the input connect them to the relays diode as show.

Now with the other USB Male connecter Connect the RED Wire to pin 6 on the relay now with the same wire connect the black wire to the Ground line as shown in the schematic diagram this is our back up battery plug.

Now using the Female part of the USB cable Socket connect the RED Wire to Pin 3 of the relay and Connect the black wire same cable to the Ground line as shown in the diagram. 

In the Photo below you can connect a component off cut to the + input line and run it down to pin 2 on the relay,

Then using a second component lead off cut connect it to pin 5 and 3 then solder it to both pins on the relay.

Block Diagram below of Relay bridge wires



E-Mail me: anthony517654@gmail.com