Lab5.docx

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Electrical Engineering

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Jan 9, 2024

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ECEN 214 - Lab Report Lab Number: 5 Lab Title: Operational Amplifier Application- Electronic Security System Design (2/2)

Introduction and Goals: This lab is a continuation of Lab 4. In lab 4, we designed a circuit that included an IR emitter, photo detector, current to voltage converter, signal amplifier, comparator, and LEDs. In lab 5, we will be adding a latch to this circuit in order to prevent the LEDs from instantly switching when the IR emitter and photo detector become unobstructed. ● Build and test the electronic security system. ● Determine what values of resistors and reference voltage worked best for each component. Procedure: For this lab, we were tasked with building a security system using the components that we learned about from last week’s lab. The components were: an emitter and detector, a signal amplifier, and comparator. The way the circuit worked was that when the emitter and detector were unblocked from one another, the signal amplifier would have a high input voltage from the detector which would then intensify the voltage at the output of the signal amplifier. This would then be the input for the comparator which would be compared to the reference voltage. This would then output either a high voltage which would light up the red led or a low voltage which would light up the greed led. In task 1, the components from lab 4 are combined into one circuit. The design of the circuit should allow the output of the comparator to be at +5V when the light beam is unobstructed and at 0V when the light beam is obstructed. The circuit combining the IR emitter and photo detector is shown in Figure 1. The non-inverting op-amp is then constructed as in Figure 2. The voltage comparator is then constructed as in Figure 3. Figure 1: Block diagram of components from Lab 4.

Figure 1: IR emitter and Photo detector component. Figure 2: Non-Inverting Op-amp Figure 3: Voltage Comparator in lab. Figure 4: Bench equipment for op-amps positive and negative supply

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In Task 2, we connect the output of task 1 to the latch circuit. This overall circuit is shown in Figure 5, where the latch circuit is the right-most component on the Diligent breadboard above the two LEDs. When it's needed to reset the latch, connect a wire to the R input of the latch. Then connect that wire to the ground briefly and that should reset the latch. In Task 3, connect the two LEDs to the latch output (Q) from task 2 as shown in Figure 5. Choose resistor values for the LEDs to prevent the LEDS from burning out. Figure 5: The entire electronic security system. Discussion: For the emitter we chose a 200 ohm resistor for the emitter because it resulted in a high current to flow through the emitter, which would also result in a high intensity of IR light incident to occur. For the current to voltage converter, we used the op amp because it resulted in more distinct values for the high and low voltages, depending on whether the emitter was obstructed or not. For the detector we used a 100,000 Ohm resistor because it increased the voltage that would be output from the detector which would then be amplified when used as the input for the signal amplifier. We used the non inverting amplifier for the signal amplifier because it would give us a positive voltage as an output, rather than the inverting amplifier which had given us negative voltages as the output for different voltage inputs. We chose an amplification factor of 4 which allowed us to create a strong output voltage and have a noticeable difference between the highs and lows. For the signal amplifier we used a 1,000 Ohm, 2,0000 Ohm, and a 3,300 Ohm resistor. For the comparator we used 5V as our reference voltage because the output voltage from the signal amplifier would either be greater than 5V or less than 5V which would act as our

middle point. We put the reference voltage on the negative input for the comparator because the output voltage will create a positive voltage if the positive input is higher than the negative input and vice versa which is what we want the circuit to do. From Lab 4, it is seen that the voltage in the amplifiers saturates when it is around 4 volts. To ensure that the amplifiers are working properly, we want the voltage to be as high as possible near the 5 volt range as it should theoretically saturate at that point. The voltage we measured was around 4.1 volts. This lab definitely had some challenges to it, mainly with making sure that the circuit was properly connected. The main way we were able to solve this problem was by testing each part of the circuit to make sure that each part was properly connected and functioning before adding the next step to it. This helped us make sure that the circuit was giving us the proper outputs for the next part without having to go back and find the part that isn’t working. Conclusion: This circuit was able to properly work as it was intended. We were able to determine which resistors values and reference voltage we wanted to include in the circuit in order for it to work properly. Therefore, the lab goals were fulfilled. The distance of the emitter and detector was limited just because of how we had wired the circuit, but it was working as it was intended. Signatures: