Atmel AVR Microcontroller projects


Posted on Feb 5, 2014

Using an Atmel ATTiny2313 microcontroller and an HD44780-compatible character LCD display, along with a reed switch and some magnets, I was able to construct a tiny speedometer/trip computer for a soapbox derby cart. It measured the speed of the cart using a permanent magnet attached to the rear wheel`s rim, and a stationary reed switch attached t


Atmel AVR Microcontroller projects
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o the soapbox derby cart. Every time the wheel revolved, the magnet would pass by the reed switch, thereby momentarily opening it. The microcontroller calculated the speed of the cart simply by dividing the circumference of the rear wheel by the period of the wheel`s revolution. This project was motivated by a problem I heard about from a friend. At the Burger King where he works, employees should take no longer than three minutes to build a burger; however, at his Burger King, no way to measure your burger-building time was supplied. Initially, I suggested buying a watch or an egg-timer from the local dollar-store, but I was soon reminded of why that was not a great solution: it was too easy and rather boring. The timer had to do one very simple thing: it had to count down from 3. 00 minutes to 0. 00 minutes and then beep. Consequently, I designed it to be very easy to operate. It had just one button - a very large, red one - that the user would press to turn on the device and start counting down from 3 minutes. Pressing the button while the count was already in progress would simply reset the count to 3 minutes. When 3 minutes elapsed, the device beeps for 1 second, and then switches to a low-power mode. I used a 32. 768 kHz crystal and a PIC16F84A microcontroller as the heart of the device, taking advantage of the PIC`s low-power "sleep" mode so that one-button operation would be possible. There is no need for an "off"...




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