LEARNING TO READ SCHEMATIC DIAGRAMS So far you have been constructing the circuits by following the detailed pictures in the textbook. For example, you were following the pictures to connect the LED between positions A2 and B3 on the white board. Now that you have become more experienced, it is time to learn how to construct your circuits by following schematic diagrams. For example, the diagram below shows the circuit for Exercise #1 in our textbook, in which you connected an LED to the RedBoard. Look closely at this schematic diagram, in thid class you will be asked to construct this circuit WITHOUT using the textbook! ALWAYS CONNECT THE BLACK AND RED WIRES FIRST! The first thing we always do in the circuits, is to connect a RED and a BLACK wire between the whiteboard and the RedBoard. Use the BLACK wire to connect one of the minus (-) holes in the whiteboard to the GROUND pin of the RedBoard. Use the RED wire to connect one of the plus (+) holes in the whiteboard to the 5 Volts pin of the RedBoard. All the wires are the same, but we use RED and BLACK to remind ourselves what these connections are (RED=plus=hot, BLACK=minus=cold). See the picture below: 1
NEXT, FOLLOW THE ELECTRONS! The diagram contains an LED and a 330 Ohm resistor. It looks like one end of the LED is connected to Pin#13 of the RedBoard, and the other side of the LED is connected to one end of the resistor. The other end of the resistor is connected to the Pin GND (GROUND) of the RedBoard. Try to imagine you are an electron at the top of the diagram below. You are leaving Pin #13 of the RedBoard, go through one end of the LED (you need wire#1 for this), exit the other end of the LED, then you enter the Resistor (you need wire#2 for this), exit the other end of the resistor, and finally you sink or disappear into the Ground (GND) (you need wire#3 for this). You remember that Ground in all of our circuits is one of the minus (-) holes on the whiteboard. So wire #3 must connect the LED to one of the minus (-) holes on the whiteboard. You need to be careful with which end of the LED is the top end (connected to Pin #13 of the RedBoard, and when end of the LED is the bottom end (connected to the Resistor). The rule is, the arrow in the diagram is the plus side of the LED (i.e. the longer leg of the LED), and the other end is the minus side (i.e. shorter leg of Ground leg of the LED). + LONG LEG - SHORT LEG Exercise #1: BUILD THIS CIRCUIT, then TEST it by running example #1 in the Arduino menu. 2
EXERCISE #2: A MORE COMPLICATED EXAMPLE, THE RGB LED In a previous class you connected a triple-led, also called an RGB LED. Build the schematic circuit below. The only additional information that you need is the schematic of the RGB LED, shown above. Exercise #2: BUILD THIS RGB CIRCUIT, then TEST it by running example #3 in the Arduino menu. EXERCISE #3: MANY LEDS In a previous class you connected 8 LEDS to the Arduino. Build the schematic circuit below. Exercise #3: BUILD THIS MANY LED CIRCUIT, then TEST it by running example #4 in the Arduino menu. 3
EXERCISE #5: PUSHBUTTONS In a previous class you connected two pushbuttons and an LED to the Arduino. Build the schematic circuit below. Notice that the left-hand side is the same as in the first circuit you built today, so it should be relatively easy to set up. Now let s look at the right hand side, where the pushbuttons are. Imagine you are an electron at the top of the diagram, at the 5 Volts connection. Immediately you remember that 5 Volts is connect to the + holes in your whiteboard. This means that you can make the 5 Volts connection to any of the holes in the + row of the whiteboard. Now look at the diagram below. If you are then an electron at the top of the diagram, it looks like you can move either to Resistor #1 or to Resistor #2. So the top of this diagram will require two wires, wire #1 and wire #2 as shown here. WIRE #1 WIRE #2 WIRE #3 WIRE #5 4
Now you are the PUSHBUTTON, which must be placed nicely across the middle of the WhiteBoard, as shown here: When you exit the Resistor #2 on the right of the diagram, you can go in one of two ways: either you go to the PUSHBUTTON, or you go to the PIN #2 of the RedBoard. So you need two wires, Wire #3 going from the Resistor to the Pushbutton, and Wire #4 going from the PUSHBUTTON to PIN #3 of the RedBoard. Notice the dot in the diagram, it shows clearly that there are two wires connected at the same point. The best way to connect two wire to the same point is to use one of the vertical rows of the Whiteboard, as shown below. All three holes shown here are automatically connected to the same point, under the surface of the whiteboard. 5
Continuing to follow the electron, when you exit the PUSHBUTTON, you can travel to the GND (Ground). The easiest way to connect this again, is to connect the exit of the PUSHBUTTON to one of the minus (-) holes of the whiteboard. WIRE #1 WIRE #2 WIRE #3 WIRE #5 Finally, you need to repeat the connections for the second Resistor, and for the second PUSHBUTTON, which are connected to Pin #3 of the RedBoard. Exercise #4: BUILD THIS MANY LED CIRCUIT, then TEST it by running example #5 in the Arduino menu. You must complete all these exercises this week. ALL CIRCUITS BUILT: Grade=A 3 OUT OF 4 CIRCUITS BUILT: Grade=B You will get a similar circuit to build in your midterm exam, so it is important to be able to follow the electrons and the required wires around any circuit! 6