This week the team completed preparations for testing the Power Supply. Construction of the supply with switching regulators was completed.
Team
The team met on Tuesday 2/8 to conduct testing of the Linear Regulator Power supply. The supply failed almost immediately, With the 12V supply falling to 11V under the maximum expected load condition. This is well above the specified 5% tolerance.
Luckily, the team had already begun working on a Switching-based supply using LM2576 Buck regulators that had been purchased when a Battery-based supply was under consideration. These regulators can supply up to 3 ampere of current each and reach significantly lower temperatures under normal operation.
The team had planned to meet on Thursday to test the regulators, but John became ill with the coronavirus and self-quarantined for the remainder of the week.
John
Unfortunately, John was contracted COVID-19 this week. He started experiencing symptoms on Wednesday (2/9) and received a positive result from a PCR lab test on Thursday (2/10). After contacting the COVID-19 management office at Valencia, he was instructed to remain in isolation until the Tuesday 2/15.
During his quarantine, John worked on completing the power supply.
LM2576 Buck regulators were used to replace the 12V and +5V linear regulators to reduce the amount of heat generated by the supply and increase the accuracy of voltage regulation.
Construction of the final board required two attempts. Efficiently populating the generic perf-board PCB proved to be a slight challenge. A short time-lapse video of the process can be seen below.
The final board:
The Power Supply prototype board was completed on 2/13
Further PSPICE Simulation of the Preamp was conducted in preparation for breadboarding. A 4th Order Bessel Low Pass with a gain of 2.8 was added to the Preamp and simulated.
dB Voltage Magnitude Plot of each stage output (Green: 2nd Order HPF, Red: 2nd Order LPF added, Blue: 4th Order LPF with gain of 2.8 Added)
A gain of 2.8 will ensure no clipping of the ADC inputs
Voltage group delay of each stage (Red: Stage 1, Pink: Stage 2, Yellow: Stage 3)
Group delay at 50Hz is actually lower after the third stage. This will need to be verified in bench testing.
Hunter
This week, Hunter updated the “weekly minutes with the professor” page.
An alarm circuit was made to continue testing and practice programming the Arduino Mega and TFT LCD to read and display the output value from an input pin of the Arduino to the LCD. This program is capable of comparing the output values by using the Arduino IDE Serial Monitor tool, within the application.
Below is a quick example of this circuit and how the alarm is activated by using a bright light. The light activation could have been avoided, and instead programmed so the PWM is activated on its own, but this seemed more fun.
Once this is programmed to display the output on the LCD, a second circuit will be made using the same concept but to display the output coming from a small electret microphone, which is more comparable to the LCD's purpose of being implemented in the design.
These tests are done in attempt to minimize risk of any possible damage to our final design once it's ready for this step, and also for learning purposes as well.
The video below shows a (back up) 240W ATX PSU power supply, doing a very basic load test at home using a 50W load resistor to verify that it works as intended. If needed, the normal bench tests trials will be done on campus, but we are currently using those as many lab time slots for the the parts that we are certain will be used in the design, so we do to not waste any time.
This video shows an Arduino nano, using its 3.3V input port, provided by the 3.3V output of the 240W ATX computer power supply. This is another basic, at home, load test for verification that the PSU can work with a device (Arduino Nano) that is fairly similar to ours device, which also has a 5 and 3V supply like our Arduino Mega 2560.
The Nano is tested as the load. The Nano is also an extra Arduino device that we already owned and is not of importance. It is also cheap incase something were to happen to it while testing.
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