Step 1: A Preview of the Flashing LED Dog Harness
Step 2: The Battery Pack
Step 3: The 555 Timer Circuit
Just follow the instructions at the vid for more info in making the 555 timer circuit.
*** I used a film canister to hold the circuit and I cut it half for it to fit in the pouch.
Step 4: The LED PCB and the Overall Circuit
*** I used the wires from an old cellphone charger as my connectors..
*** You can use spst switch for the switch...