Department of Electrical Engineering and Electronics ELEC171 Project Practice activity 2: Using Integrated Circuits (IC) Overview The main aim of this activity is to give you some experience of setting up an integrated circuit (IC) chip, because you will need these in your robot car project. Integrated circuits are components that contains a particular circuit already made, which you as a user can access with one or more inputs, and one or more outputs. You are probably already familiar with the most complicated examples of these chips, namely the processor chip in your phone or computer, made by Intel or some other company. Most of the ICs that you will see in the lab will be much simpler than this: chips that are made with just one specific circuit in them. One feature of ICs is that they contain many components inside them - perhaps a complicated combination of resistors, capacitors, transistors, and diodes. You, however, don't have to wire those components yourself - all that is done for you inside the IC. You just have to connect the appropriate inputs, and the IC will generate the appropriate outputs. The reason you are testing ICs is because these will be incredibly useful in your robot car project. You will have to use at least one type of IC and probably several of them, depending on your design. There are different types of ICs that might be useful to you. In this activity, you will test 3 different types. The specific aims of this activity are as follows: ● to give you experience of using several different types of integrated circuits to give you experience of using a comparator IC, which is an essential part of most sensor circuits to give you experience of using a voltage regulator IC, which allows you to control the DC voltage used in different parts of your robot car circuitry to give you experience of using a H-bridge IC, which will be useful in controlling the motors in your robot car. Activity Specifications Activity name Suggested study time Assessment Submission deadline Submission format Late submission Resit opportunity Marking policy Anonymous marking Feedback Using integrating circuits 5 hours Lab notes for the three practice activities will be assessed together. In total, this will contribute 30% of your project mark. Lab notes due on Online via Canvas Standard university penalty applies August resit period Marked and moderated independently Yes via Canvas / Turnitin Feedback Studio 1 Assessment The assessment of this activity consists only of your lab notes for the three Project Practice Activities, which are scheduled for the first 3 weeks of the semester. ● ● Your lab notes must be uploaded to Canvas on your lab day in Week 3 of the semester, after the 3rd practice activity. The dates are depending on your lab day. You should upload your notes as a single pdf file. You should scan your notes after your complete the 3rd practice activity and submit this pdf file. Your marks for the lab notes will comprise 30% of your mark for the ELEC171 project. The marking guidance for these laboratory notes is the same as for the laboratory notes marked in Semester 1. You can find the marking guidance and marking criteria on the module website. 2 Part 1: Background: ICs and components 1.1: Identifying your components You will use several ICs for this activity. You might have a kit of parts with the ICs already in it, or you might have to collect the ICs from the technician's area. When you have your components, you should identify each one now, so that you know the correct one to use for each of the circuit activities explained later. Figure 1.1 shows one of these IC chips, called an LM393 chip. The third photo shows the writing on the plastic casing that allows you to identify the chip. Each of the ICs in your kit should have its ID number written in a similar way. 30 ● L293D H-bridge chip 05AHJ803 Figure 1.1: Three different photos of a LM393 chip, showing the chip itself, the chip inserted into a test board, and a close up of the identifying information written on the plastic case. O 3934 Go through the part list below and check that you can match each component with one of the parts on your desk. If you don't have one of these components, you should be able to collect it from the technician's area. 7805 voltage regulator LM2940 voltage regulator LM393 comparator chip a variable resistor you should already have one of these in your kit. If you do not have one, you should take a 1k variable resistor from the resistors/capacitors cupboard in the lab. 3 2.1: Background Part 2: Testing a comparator IC The aim of this activity is to give you some experience of using a comparator circuit. Using an IC that contains comparator circuits, you will set up the chip on your test board, attach some inputs, measure the outputs, and see how this type of chip could be useful for your robot car design. The purpose of a comparator circuit is simple. The circuit has two inputs and one output. The circuit compares the two input voltages and gives an output voltage that is different depending on which input is larger. When used in a practical circuit, the two input voltages usually are: a reference signal for which you know the voltage a test signal with unknown magnitude. i. ii. If the test signal is larger than the reference voltage, then the circuit output is a (pre-set) high voltage. If the unknown signal is lower than the reference voltage, then the circuit output is a (pre-set) low voltage that is usually zero. Figure 2.1 contains several different representations of a comparator. The first image shows the principle, with two input voltages V₁ and V₂, and an output voltage Vout. The circuit itself (which you should remember is composed of many components set up inside the IC) is represented by the triangular shape. The second image shows the same circuit, but with the two supply voltages that are needed to make the IC work. As already mentioned, the IC is a circuit, and all ICs require you to power the circuit by connecting a power supply. In a circuit diagram, the power supply connections are indicated as shown in the figure, with connectors for Vcc and VEE. For the comparator circuit, these voltages should be a positive voltage for Vcc and a ground connection for VEE. The third image shows a more complete circuit that contains a comparator that compares V₁ and V₂ and then generates the appropriate output. Figure 2.1: (a) a simple diagram showing the principle of the comparator; (b) a more complete diagram that shows that the comparator circuit has to be powered by two supply voltages (VEE is usually zero); (c) a circuit diagram showing a comparator in use. In this case, the comparator is powered by 5 V supply voltage, and should give an output of 5V or 0 V, depending on the relative values of V₁ and V₂. V₁ V₂ (a) + Vcc=5 Vo- V₁ VEE=0 V o V₂ Vout + (c) V₁ O V₂ (b) R₁ + +V cc Vo out VEE Vout 4 2.2 Identifying the parts of your comparator chip You have been given an integrated circuit called a LM393 chip. This chip contains two identical comparator circuits. You can choose to use only one of the comparator circuits, or both. Figure 2.2(a) is an image from the technical data sheet for this integrated circuit. You can see that the connections to the IC, each of which corresponds to one metal leg of the plastic casing, are labelled in a particular way. 1OUT 1 1IN-2 1IN+ 3 GND 4 8 Vcc 7 2OUT 62IN- 5 2IN+ Vout V₂0 V₁0 all VEE=0 V 1OUT 1 1IN-2 3 1IN+ GND 4 8 Vcc 7 20UT 621N- 521N+ Vcc=5 V (a) (b) Figure 2.2: (a) a schematic of the LM393 comparator chip, taken from the technical data sheet; (b) a diagram showing how you might wire up the chip in a real circuit. This IC has eight pins. Pins 8 and 4 are used to connect the voltage supply. These pins must be connected to make the internal circuitry of the IC function properly. The other 6 pins are used for the comparator circuits. Pins 1-3 are used for one circuit, and Pins 5-7 are used for the other comparator circuit. Figure 2.2(b) shows how the first comparator on the chip should be wired up in a practical circuit. (Note that the input pins are labelled "+" and "-". You must take notice of details like this. 2.3 Setting up a comparator circuit The aim of this activity is to wire up this IC and carry out a few tests to confirm your understanding of how a comparator works. For the tests below, you will need to set up the IC on your test board. Figure 2.3(a) shows the best way to mount the chip on the test board, with legs on either side of the central blank region. This arrangement allows you to connect different wires to all the different legs. When you set up the IC, you need to make sure you know the orientation of the IC on the board. The chip shown in the figure has a little circle to help you keep the chip in the right direction. Most chips have something like this. (Another common indicator is a semi-circular notch in one end of the plastic case. Some of the other ICs in your kit have this type of indicator.) The aim of this experiment is to build and test the circuit in Figure 2.3(b). You should follow the steps below, and keep a record of your experiment in your lab notebook. Construct the circuit in Figure 2.3(b) with Vcc = 5 V, and R₁ = 470 . You will need to use the different outputs of your DC power supply to set up this circuit. Use the constant 5 V output for Vcc and VEE, and the two variable voltage outputs for V₁ and V₂ 5