Programmable Timer

The task was brought forward to create a simple to use and cost effective programmable timer with a LCD character display. From what i had laying around on the desk the following plan was devised:

The design is fairly straight forward, the whole project is based around the ATMega8L microcontroller as this has enough I/O to run a 2×16 LCD character display and the various push button switches needed to accomplish the task.

The design incorporates the following:

  • Backlit 2×16 LCD Character Display
  • Atmel ATMega8
  • 6 x Tactile Push Button Switches
  • LM7805 Voltage Regulator
  • Standard Atmel reset circuitry

Below a scehmatic of the circuit can be seen.

The timer has a basic regulated power supply, the Atmel standard reset circuitry, Tactile switches for I/O and the LCD. The whole timer is designed to run from a 9V battery or 4xAA batteries.

One thing that is perhaps strange about the PCB layout is that the microcontroller is on the underside of the board, this was done to minimise vias to make life slightly easier. A prototype has been built and is just waiting to be programmed.

The tracks in blue are the bottom layer, the tracks in red are wire vias on the top layer. This board also has an ISP6pin header which really isnt needed but was added to make programming simpler.

In the future i hope to surface mount the majority of the componets including the microcontroller and resistors this should make the timer look slightly better and more professional.

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