Microcontrollers

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Microcontrollers

• An Introductory Course

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What is a Microcontroller ?
A microcontroller is often described as a
computer-on-a-chip. It is a low-cost integrated
circuit that contains memory, processing
units, and input/output circuitry in a
single unit. Microcontrollers are
purchased blank and then programmed with a
specific control program (OPROM). A more
versatile chip is one that can be reprogrammed
many times (EEPROM) Once programmed the
microcontroller is built into a product to make
the product more intelligent and easier to use.
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Role of Microcontrollers in our life

• Quote from Dataquest Industrial Analyst (USA)
  In 1999 the embedded market used approximately
  5.2 billion microcontrollers a year, compared to
  346 million microprocessors for PC, or 15 times
  as many microcontrollers as microprocessors.
•  These omnipresent microcontrollers are found in
  practically every industry, such as
  telecommunication, food processing,
  bio-electronics, ICT and automotive.

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• These are your remotes, watches, calculators, CD
  players, Gameboys, sensor lights, alarm systems,
  stereos, VCRs, Digital cameras, washing machines,
  remote locking auto doors, GPSs, depth
  sounders, bar code readers, pace makers, and
  millions of other devices that we take for
  granted.
• 3 million cows in Australia will be tagged
  with microcontrollers (similar to the one used in
  the FunLED), which will be used to gather
  important health information of the cows.
  Millions of smart cards are made from these chips.

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Typical Microcontroller- PICAXE Chip
In industry microcontrollers are usually
programmed using the assembler or C programming
languages. These require a lot of training and
practice to use. The PICAXE system overcomes
this problem by use of a much simpler, easy to
learn, BASIC programming language (this is also a
common Industry standard) Programs can also be
created graphically by use of the flowchart
editor e.g. PIC LOGICATOR The PICAXE system also
has a programming compiler on board the chip
saving extra hardware or software to do the job.
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What is the PICAXE system?

• The PICAXE system exploits the unique
  characteristics of the new generation of low-cost
  FLASH memory based microcontrollers.
• These microcontrollers can be programmed
• over and over again (typically 100 000 times)
  without the need for an expensive programmer.
• The PICAXE uses a simple
• BASIC language
• (or graphical flowcharts).

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• Typical PICAXE CHIP

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Basic Circuit Layout
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The Control System
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Adding Outputs

• Small outputs from a chip use low currents and
  require a current limiting resistor.
• LEDs run about 10mA and so require around 330mO
  resistor.
• A Piezo speaker can run with no resistance
• Motors use high currents and usually need a
  separate power source or amplifier.

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Adding Inputs

• Switches and variable resistors (LDR) can be
  connected to the microchip using a 10kO pulldown
  resistor.
• The input pin is between these two creating a
  voltage divider.

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A system of inputs and ouputs
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The Remote Control
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Step 1Draw your circuit (Crocodile Technology)
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STEP 2 optimise your wires (PCB wizard)
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Step 3 Expose the OHT onto the board (Light
Box)Remove unwanted copper with chemicals
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Step 4 Drill the holes
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Step 5 Solder the components
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Step 6 Program the microcontroller