LAB4 - Lab 4 Operational Amplifier Application Electronic Security System Design Part 1of 2 Theory Introduction Goals For Lab 4 In Lab 4 and Lab 5

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Lab 4: Operational Amplifier Application: Electronic Security System Design: Part 1 of 2 Page 1 Lab 4: Operational Amplifier Application: Electronic Security System Design: Part 1of 2 Theory & Introduction – Goals For Lab 4 – In Lab 4 and Lab 5, you will design, build and analyze an electronic security system using a laser diode, a photo detector, operational amplifiers, resistors, a comparator, a latch, light emitting diodes and a buzzer. The main task is to build a circuit that will detect an interruption in a laser beam and sound an alarm. You may use an idealized model of the op-amp for your calculations to simply analysis. In Lab 4, you will use an op-amp as a current to voltage converter, as a signal amplifier and as a comparator. In Lab 5, you will use an op-amp as a buffer. Please review Chapter 5 of your textbook regarding the uses of op-amps. Theory – The block diagram of the system is shown in Figure 4.1. The stages to be build and tested today are enclosed in the box. A laser diode, part no. DL3149-055, is employed to send a red light beam to a photo detector, part no. FDS100. The photo detector current induced by the light beam depends on the strength of the beam. An operational amplifier, or op-amp, will be connected to the photo detector to convert the current into voltage. Since the output of this first stage is very small, a second op-amp will be used in an inverting amplifier configuration to increase the signal level so it can be used in a comparator. After the voltage is amplified, it will be sent into a comparator. In Lab 5, you will build a latch to help isolate the signal from noise, a buffer to supply the current needed, and a system of LEDs with a buzzer to serve as the alarm. In the end, whenever the beam is obstructed, the comparator output will be changed. It will then be locked by a latch circuit and a buzzer will sound. Light Emitting Diodes (LEDs) are used to show the status of the output. Laser Diode Photo- detector Current-to-Voltage Converter Signal Ampifier Signal Comparator Latch LED & Buzzer Figure 4.1 Working with a laser diode in lab requires extra safety procedures. Never point the laser diode at a person. Instead, be sure that the laser points directly at the photo detector. The safety sheet agreement you signed during the first lab is still in effect. If you treat the laser as a toy, you will find yourself removed from the lab and receive a 0 for all work on Labs 4 and 5. When you are performing the lab, pay special attention to stage 3 and stage 4. Although the hardware of these stages is very similar, stage 3 converts current to voltage and stage 4 amplifies the input voltage. Operational Amplifiers: For analysis purposes, the ideal op-amp has two inputs and one output. The inputs are referred to as negative and positive. The output voltage is determined by the input voltages and a network of resistors, or other elements, attached to the op-amp.
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Lab 4: Operational Amplifier Application: Electronic Security System Design: Part 1 of 2 Page 2 The ideal op-amp characteristics are:
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This note was uploaded on 02/22/2009 for the course CHEN 222 taught by Professor Johns during the Spring '09 term at American Academy of Art.

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LAB4 - Lab 4 Operational Amplifier Application Electronic Security System Design Part 1of 2 Theory Introduction Goals For Lab 4 In Lab 4 and Lab 5

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