Introduction

Many materials are available on which to build prototype circuits. The material chosen will depend on the required life and use of the circuit. For laboratory use or other short-term applications where a permanent circuit is not needed and operating frequency is below 10 MHz, solderless breadboards such as that shown below can be used.

The board comprises:

• 3 breadboards on which your circuits will be mounted
• A 5 volt power supply required for all logic chips
• A variable frequency clock which operates in either manual or free running mode
• 8 switches, which can provide inputs to your circuit
• 2 push button switches (not debounced)
• A debounced push button switch
• Two 7-segment LED display
• A 10x7 led array
• 8 user input LEDs
• A potentiometer

There are three banks of LEDs on the left hand side of the board for signal output:

• At the top there is a pair of 7-segment LED displays which are connected via PALs. The PALs have been configured to do binary to 7-segment hexadecimal character conversion. Inputs A to D provide the binary inputs.
• In the middle there is an LED bar graph. 8 of the LEDs are connected via a buffer. The other two indicate when the power is on and the state of the clock.
• At the bottom an you will find an LED matrix. The column decoding is provided by a 4-to-16 line decoder (inputs A to D) and the row value is supplied via a buffer (inputs 0 to 6).

Before you start read through the sections on:

• Appendix A - Using the breadboard
• Appendix C - Resistor colour codes
• Appendix E - Datasheets for the chips you will be using

All of the workshops should be written up in full. From your notes it should be possible for somebody else to be able to reproduce your work. This is good scientific practise. When an exercise is complete and written up, including answers to the questions, the final page will be signed by a demonstrator and a tick entered in the tick sheet.

VERY IMPORTANT: you need to hand in this assessed exercise as part of your portfolio of work at the end of the year (see the Head of Department's notice), SO YOU MUST KEEP YOUR WORK!