A mini-project for the course 4180 Embedded Systems at Georgia Tech.

Overview:

Ever late for your exams because of the alarm was too easy to snooze off. Why not have an alarm clock which runs away when you try to reach for the snooze button!

Youtube Link ! http://www.youtube.com/edit?video_id=bBWHCuVjuBM&ns=1

List of Hardware Components

• Mbed LPC 1768 http://mbed.org/handbook/mbed-NXP-LPC1768
• Nokia LCD Display https://www.sparkfun.com/products/11062
• Sonar Sensor https://www.sparkfun.com/products/8501
• Speaker https://www.sparkfun.com/products/9151
• Red Bot kit ( Wheels + Motors + Base) https://www.sparkfun.com/products/12032
• H Bridge ICs
• Push Buttons - 4 https://www.sparkfun.com/products/97

Connection for Individual Components

Push Buttons Push Buttons http://mbed.org/users/4180_1/notebook/pushbuttons/ The debounce was used to our advantage, all connected to digital in of the mbed. The project required 4 push buttons(PB). One for indicating the clock to reset the timer, One each for incrementing and decrementing the Digit counts while setting or resetting the values for hour and minute.

Nokia LCD http://mbed.org/cookbook/Nokia-LCD The LCD is required to display the real time; ask the alarm-hour and alarm-minute to be set from the user. LCD uses a SPI interface, but a library is already available and this was used by us.

Sonar Sensor The Sonar provides a simple analog output.

Speaker Speaker plays police siren as the alarm tone. A BJT 2N3904 is used to drive the Speaker.

H Bridge

Both motors driven by a single external 9 volt battery connected to the supply terminals of h-bridge

Problems Faced

• The Battery and USB current and regulated voltage problem. Once all the peripherals are connected. The LCD display draws a 100+ mA of current. The mbed draws a current of 130 + mAmps in normal mode. The Vout of the mbed is a regulated output providing much less voltage than 3. The H bridges start showing erratic behaviour. Maintaing separated batteries for motor supply and peripherals and mbed power helps and solves the above problem.
• The push buttons can be used to call interrupt sub routines provided they are properly debounced. Our main loop was kept running without delays hoping to sample at least once.

Possible Improvements

1. The real time clock can be kept on running by using the input Vb of the mbed.
2. Attach IR sensors to detect walls and turn accordingly
3. Speed Control if the person is too near
4. Provide a way to set the alarm and the clock using an APP
5. The Bot can be even made to rotate after a certain period of time, ( just reverse the direction of the motors w.r.t to each other) if the sensor is not being activated and the volume can be increased. The rotating can also serve as taunting the person trying to catch. The added advantage would be if the sonar sensor is kept tilted to and angle with the vertical, it cover a greater scope searching for the incoming person.
6. Mbed can be used in a power save mode to shut of the unused peripherals. http://mbed.org/handbook/mbed-NXP-LPC1768