Simple circuit for a Arduino

Job ID: 35847914

Budget: $10 – $30 AUD

I would need Simple circuit design that does the following 2 tasks for a 5V arduino pro mini

1. Power the Arduino (5V) from a car Battery (12-16V) including protection circuit.
The Arduino should keep Power for about 5 seconds after the Battery power is switched off
2. Take a 12-16 V square wave and reduce it to a 5V Square wave via a opto coupler so it can be used with a digital input

I don't need a PCB Layout