If you are a rocket modeling hobbyist and need simple and reliable rocket timer with adjustable time this project is for you. Timer can be set from 1s to 15s by using 4 dip switch IC. Depending on switch binary position 2^4=16, the time is set when second stage of rocket has to be ignited.
Project is based on common PIC16F84 running at 4MHz. MICROCHIP TC4422 is used to control the voltage and current to the “igniter”. Timer also has two failsafes to avoid accidental ignition. Device is powered from 9V battery and is small size as weight is critical in rocketing. Program is written in assembly language. [via]
Simple 1s to 15s rocket timer - [Link]