[Uploaded Sep08] PIC Driven Electronic Timer with 6 LED Time Indicators

By: Andy & Rose Morell

We made this timer, firstly so that I could use it for an exercise timer, as the timer was electronic, I couldn't see how much time I had left, so we went back to the drawing board and came up with the idea of having LEDs to tell us how much time was left. We designed it so that 6 LEDs would go out, one at a time after each 1/6th of the whole time interval had elapsed. I could then see how much time was left before I had to stop.

I also found it useful for cooking. If I was cooking several different items with different cooking times I could set the timer and could then leave the kitchen if I wanted, taking the timer with me for example if the potatoes took 30 minutes and the eggs took 15 minutes I knew whwn the 15 minutes was up because % the LEDs would have gone out.

The timer uses 7, 5mm LEDs - one for a power indicator and six for the time indicators. When the timer starts, all the LEDs light up. After each 1/6th of the set time has elapsed on of the LEDs extinguishes and this continues until all the lights are out. The LEDs then flash on and off and a piezo bleeps. The PIC chip then turns the unit off to save batteries after 10 seconds. This is accomplished using the `sleep' command.

The control programme is written in assembly language of the PIC chip 16C84. The 16C84 is a member of a family of modern micro-controller chips called PICs.

A printed circuit board has been designed for the timer and a complete kit for the timer can be obtained from us at our address below. Two `AAA' batteries power the unit and the PCB, rotary switch and batteries all fit snugly in a pre-drilled plastic box from Maplin. The order code is ZB 17, remember the box is included in the kit but not the batteries.

The total time selected will change with the time intervals of the extinguishing LEDs. The 6 way rotary switch has positions for OFF,2,10,20 and 30 minutes, the time intervals between each LED extinguishing then being - 20, 100, 200 and 300 seconds. We will be happy to supply further information about the timer or details of other projects.

PIC Timer

PIC Code 1

PIC Code 2