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ELEC2645 Project - Specification

Former Member

ELEC2645 - Embedded Systems Project - 'Sensor-matic!'

 

The aim of the project is to create an interface between a distance and a temperature sensor and an LCD screen.

 

Project Aims and Objectives

 

Aims:

 

  • To develop a small, portable battery-powered distance/temperature sensor.
  • To read the sensor outputs frequently.
  • Display the sensors outputs on a Nokia 5110 LCD screen.
  • Provide a visual representations of the distance/temperature on the display.
  • Use an options menu to toggle various aspects of the hardware functionality (i.e. toggle the use of LEDs and sound).
  • Maximise the battery life by using as little power as possible.

 

Objectives:

 

  • The battery will be a PP3 9 V battery which is mounted onto the PCB.
  • The sensors will take 10 readings every second and average to minimise errors.
  • A timer will be used so that measurements are taken at intervals.
  • The Nokia 5110 library will be imported and used to display the value of the screen at every interval.
  • ‘IF Statements’ will be used to display the visual representation of the distance.
  • A 10 K Potentiometer will vary the selection of the options menu.
  • LEDs will light up depending on the distance (Green àààà
  • A Piezo will buzz on each iteration and buzz faster at increasing distance.
  • An efficient switching regulator will be used to minimise power-usage.
  • Sleep Modes will be used to save power.

 

Project Constraints/Components

 

Main Components:

 

  • Ultrasonic Distance Sensor (SRF02).
  • Temperature Sensor (TMP102).
  • Nokia 5110 LCD Display.
  • Powered by PCB-Mounted 9 V Battery (PP3).
  • Stepped Down using 9-t0-5 V Buck Converter (MC34062 & Associated Components).
  • Two-Layer PCB Board (100 mm by 80 mm).

 

Electronic Components:

 

  • 3mm LEDs (1x Red, 1x Green, 1x Yellow).
  • 1 kΩ Resistors (1206 Surface-Mount Package).
  • 2x Push Buttons – Change Menu Display & Invert Colour.
  • 1x Slide Switch (SPDT) – Power Supply Control.
  • Piezo Buzzer – Sounds at Regular Intervals.
  • 10 K Potentiometer – Change Menu Selection.

 

Project Specification

 

Specification:

 

  • The device will be powered by a single 9 V battery.
  • A 9 V-to-5 V Switching Regulator (MC34063) will be used to step-down the voltage.
  • There will be a red LED in parallel with the switching regulator to indicate powers on.
  • A TMP102 Temperature Sensor will be used.
  • A SRF02 Distance Sensor will be used.
  • A Nokia 5110 LCD will be used to display the data.
  • Digital buttons will be used to navigate forward and backward through screens
  • A potentiometer will be used to vary the menu option that is selected.
  • A reading will be taken every second – with an average taken every 10 seconds.
  • The display will show a bar which fills in as the distance/temperature increases.
  • The visual alert will be a red/green/yellow LEDs (solid colour) and when the distance/temperature is very low/high (respectively) all LEDs flash together (2 Hz).
  • A 2 kHz tone will be generated by driving the piezo with a PWM waveform.

 

System Architecture Block Diagram:

 

image

 

User Interaction

 

PCB Design:

 

  • Keep inputs and outputs around the edges of the PCB – easier user interaction.
  • Put the Screen in the middle of the PCB and make it unobstructed
  • Include sensors at the edges of PCB (especially SRF02).
  • The distance sensor needs to be above the screen and facing out so the user can hold it in front of them to measure a distance.
  • B1 and B2 are simple buttons to navigate backward and forward (respectively) between the menu screens.
  • The pot is located at the bottom of the board in its own space so it can be adjusted.
  • The switching regulator will be underneath the screen.
  • The switch, SW and LED1 are power-related components. The switch is used to control the power and the LED is an indicator to show it is on.
  • LEDs: LEDR, LEDY and LEDG are used as visual indicators.
  • The reason the vertical edges of the PCB are kept fairly clear is because the mbed has to be soldered on the underside as well as a battery pack.
  • NB: The whole PCB will be handheld in a portrait orientation however it was rotated into a landscape position to save space.

 

image

 

Presentation on Display:

 

  • A series of menus will be used.
  • Due to screen size limitations, the maximum number of options per menu will be two if the screen is to appear aesthetically pleasing.
  • This means that 3 menus are needed:
    • 1st = Sensors or Options
    • 2nd = Distance or Temperature (Sensors)
    • 3rd = Various Options (i.e. Toggling Sound/LEDs)
  • Each menu besides the options menu will have a title.
  • Depending on how crowded the page is, a border may be added around the page.

 

  • Welcome Screen:

 

image

 

  • Initial Menu:

 

image

 

  • Sensor and Options Menu:

 

imageimage

 

  • Distance and Temperature Screens

 

imageimage

 

  • The diagram below describes the navigation through the menu screens starting from the top left.
  • The square at the side of each option appear when the specific option is selected and each arrow corresponds to the next screen that is displayed.
  • When the back button is pressed, the sequence moves back to the previous screen.

 

image