I want to make a 15 minute timer for a game. I would like it to count down 3 x 5 minute segments of time, and then ring a bell when the 15 minutes is up.
To do this, I want to push a button to initiate the timer, which will then light 3 x leds. After each 5 minute segment is up, one of the LEDs should go out. Finally, when 15 mins is up, I want to ring a bell (just once) using a solenoid.
Trouble is - I don't know where to start! My background in more in computer programming - so I understand the logic required to do it, just not how! (I've put circuits together in the past, but always using someone elses schematic - I'm not sure where to start in terms of designing my own.)
I'm not looking for someone to design it for me (though it might help!) but for an idea of where to start figuring out how to do this. Have had a look at some 555 based egg timer circuits, but don't know how you set the time periods on them.
Have knocked up a vague schematic - does it look like I'm heading in the right direction? If this does what I think it does it should begin with three LEDs switched on, then with each clock pulse knock an LED off until they're all off - then it should reset.