COVID Circuit

The goal of this circuit is to light up LEDs if any of three COVID symptoms were present. If no symptoms were present, a green LED would trigger; if one was present, a yellow LED would trigger; if two, a red LED. If all three symptoms were present, an alarm would go off. To prevent the alarm from constantly going off if, for example, the patient had a sudden coughing fit, a timer was equipped to only trigger the alarm every certain period of time.

Simulation Circuit Board

Here is our Circuit Lab design for our physical circuit for the COVID testing device. As you can see, the initial switches connect to AND, OR, and NOT gates in order to switch on the proper LEDs, which is determined by the number of symptoms present. The wires are connected to a flip flop, which changes from low to high every 30 seconds to detect new symptoms or see if any symptoms went away (in real life, the time between checks would be longer but for the purposes of time we made the checks every 30 seconds). If there are three symptoms, the alarm (pictured on the right) goes off and a flashing LED (from a timer not pictured in the simulation) goes off.

Here is a picture of the simulation when the alarm circuit is activated.

First Tested Version

Circuit Board

This logic circuit was created on a breadboard. This is our working design for the circuit, with a complicated logic system. Each of the three switches corresponded to a certain symptom ("Dry Cough", "Decrease in Temperature", "Low Oxygen"). The intended goal was for the LEDs to light up with the switches being flicked. However, because we didn't realise that the logic gates needed to be oriented in a certain direction, our design failed and there was not enough time to start over. We were able to get the timer and alarm circuits working by themselves.

Second Tested Version

Third Tested Version

Working Timer Circuit

This is our working timer circuit. The 555 chip is connected to three resistors and two capacitors. Since we did this circuit after the alarm circuit, we had some materials struggles. Through various tests and asking questions to the TA's, we were able to eliminate all of the problems that we had with this circuit and complete it.

IMG_5260.MOV

Working Alarm Circuit

This is our working alarm circuit. It was the result of several hours of work and trial and error. We had several resistor misidentifications, battery problems, and other assorted issues that had to be resolved. However, we were able to successfully create the working circuit. The alarm circuit consisted of five resistors, three capacitors, a 555 chip, a bread board, one transistor, a battery pack, and an alarm. This combination was then wired to produce the working speaker circuit.

IMG_5862 (1).MOV

Takeaways:

Despite the fact that the full circuit didn't work, the COVID project was a great way for us to learn about the fundamentals of circuits. The process of building our circuit required numerous class hours of trial and error and lots of questions for our TA's. One of the most important lessons that we had to learn was to test and re-test our equipment. We had many faulty batteries and LED's that led to hours of work that could have been avoided. We also could have saved a lot of time by checking to see if groups of the circuit worked. For example, if we tested if the group of wires and gates leading to the red LED worked, it would be easier to identify where potential errors were. We learned that checking resistor codes is extremely important and can be detrimental to an otherwise perfectly functioning circuit. Finally, we learned about how the orientation of the 555 chip on a circuit on the breadboard can impact whether or not a circuit will work. The major takeaway from the Week 1 project is to improve our short class time by getting things right the first time so that we don't continue to make the same mistakes over and over.

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