Multiplexed led display, laboratory, electronic, voltage, kohm resistor, silicon controlled rectifier, electrolytic capacitor, ceramic capacitor, switching regulator
Through a series of laboratory procedures, we have created a LED clock which is powered by a transformer whose voltage initially is a 120V rms. The purpose of the project is to understand how to use resistors, transformers, capacitors, and transistors to bring down the alternating current voltage of 120 V rms down to a safe direct current, and use that to power an LED clock.
[...] inc zh ;carry nc1_m: lpm r21,z ;read segments from data table ldi zh,high(seg_table ;load z register for indirect read ldi zl,low(seg_table add zl,r20 ;compute offset into the table brcc nc2_m ;carry required? inc zh ;carry nc2_m: lpm r22,z ;read segments from data table ret ;return delay_21k simply calls delay 21 times delay_21k: rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay rcall delay ret delay takes 1003 cycles to execute delay: ;the label that identifies the subroutine to the assembler clr r31 ;initialize register 31 (this can be any unused register) delay_loop: label for the brne instruction inc r31 ;increment r31 cpi r31,0xf9 ;compare r31 to the final value brne delay_loop ;jump to delay_loop if the count has not reached the final value ret ;return. [...]
[...] We then proceed to do the high-current power supply test. A 3.3 ohm load resistor connected to a USB plug will verify the power supply current limit if readings are between 4.75 and 5.25 then you do not need to install a resistor at R1A. Now we need to test the voltage across D5 again but in continuous mode. We notice that the image of the oscilloscope is different from before (page 5). We now connect a piece of lead 1 inch long and connect it to the scope probes, this allows us insight into magnetic fields (Westerfeld Lab 7). [...]
[...] Course Suggestion: This class was very interesting and the lectures went perfectly with labs, one thing this class should have is a recitation. Sometimes learning in a large lecture hall is not the best, such as for someone who has not taken physics, but none the less the extra laboratory videos did help a lot. The teaching assistants Yu Liu and Jane Hu are very knowledgeable and helpful. Work Cited Westerfeld, David. Lab ESE Web. Fig Clock schematic diagram. Diagram from David. Westerfeld, Lab Web. [...]
[...] We now install five 2N3906 pnp transistors at Q2 through Q6, these help the LED lights turn on (Westerfeld Lab 11). We then install a 1.2 kohm single in-line pin resistor pack (final schematic page 7). Now we can program our clock to read seconds and display time. The code on pages 8-14, has 12 methods in total. Starting with the main method it clears the registers we declared, and sets up the ports. Then we have the tick method which increments ticks, seconds, minutes, and hours, with respect to their limits. [...]
[...] Equipment used • Jameco 120 V 60 Hz 16.5 W Transformer • Circuit board • Fuse holder • 1 amp normal blow fuse • 4 Diodes • 100 kohm resistor (provides a small load to the circuit that makes the oscilloscope images clearer) • 680 μF electrolytic capacitor nF ceramic capacitor nF ceramic capacitor μF ceramic capacitor • USB connector • kohm resistor • SB560 Schottky diode • 470 μF aluminum electrolytic capacitor • LM2673 switching regulator • 47 μH toroidal inductor • TYN612 silicon controlled rectifier • DSO-X 3012A oscilloscope • Piezoelectric Buzzer • MPSA06 transistor • Microcontroller ATtiny48 • Six-pin connector • Six LEDs • Eight pin SIP (single in-line pin) package • Five 2N3906 pnp transistors • Either 100 or 220 ohm dual-in-line resistor pack RP2 • 1.2 kohm single in-line pin (SIP) resistor pack RP3 IV. Circuit Design The first piece added to the circuit board is a fuse holder, this piece is there for safety reasons, it breaks the circuit in the event of excess current (Westerfeld Lab 6). We then install two diodes in location D1 and D4. The diodes prevent electrical current from flowing in a reverse direction, this assists us change the alternating current to direct current. The voltage will now only be above the 0 voltage line, in a graph. [...]
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