_C_RC_Button

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School

University of Illinois, Urbana Champaign *

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Course

110

Subject

Electrical Engineering

Date

Dec 6, 2023

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pdf

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Uploaded by DeanLightning6647

All diodes have an anode (top) and a cathode (bottom). If the LED is inserted in reverse, it will not illuminate as the voltage is increased. Buttons and Switches and RC Time Constants Switching a Circuit Let’s build a circuit that uses two buttons to turn on and off two light-emitting diodes (LEDs). Locate two push buttons from your kit, as well as two red LEDs and two 330 Ω resistors. These resistors will have the color bands “orange orange brown” plus an additional band (likely gold) that indicates tolerance. You may use either 4 AA batteries or a 9-V battery for power. Be very careful not to short your battery when building the circuit. Be ESPECIALLY careful not to accidentally short your battery when storing or transporting your circuit. Using these parts, we will construct the circuit illustrated in the circuit schematic of Figure 1 and clearly explained in the physical diagram of Figure 2. The proper insertion of the button into the breadboard is explained in Figure 3. Figure 1: Circuit schematic for switching LEDs. How to read the resistor color code: http://en.wikipedia.org/wi ki/Electronic_color_code You will want to learn a good mnemonic like the one here: http://www.orcadxcc.org/ resistor_color_codes.html or https://www.allaboutcircu its.com/tools/resistor- color-code-calculator/

Notes: Figure 2: Physical diagram for button-controlled motors. The barrel-to-wire adaptor will be needed. T he 4xAA battery pack may be replaced by your 9-V battery. The LEDs of your kit have nice color! A barrel-to-wire adaptor

Notes: Figure 3: Multi-view projection of the button (adapted from https://www.ckswitches.com/media/1471/pts645.pdf ). Within the button, two flat wires span the gap in the middle of your breadboard. These two wires are connected by an internal metal plate (symbolized by the switch in the top-right figure above) when the button is pressed. Now, take apart that first circuit (the first portion is not graded) and build the circuit of Figure 4. Use 𝐶𝐶 = 1000 𝜇𝜇𝜇𝜇 for the capacitor, 𝑅𝑅 = 1 𝑘𝑘Ω (brown/black/red/gold) for the resistor, and a red-colored LED. Be careful about the orientation of the buttons. Remember that the connection across the button should only be made when the button is pressed. If your LED remains lit with no buttons pressed, your orientation is likely wrong. If the LED will not light, check the polarity (direction) in which it is inserted. Comment: Ordinarily, we would do this experiment using an oscilloscope to observe the voltage of the capacitor as it changes across time. In this case, we are skipping the oscilloscope and making some rough observations about the time constant using the visible evidence of current flow afforded by the LED. If you are inclined to play with the oscilloscope, please do!

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