It was a big week for the Hot Shocks, both in terms of project progress and group bonding. The heaters from Omega arrived this week and, with the assistance of Alex and Spencer, we began to assemble and test our hardware. Two 3x3” heaters wrap around the body of the shock and are secured by zipties, as can be seen in the picture below. The heaters are wired in parallel and powered by household 110 VAC - whether they are on or off at any given time depends on the state of a solid-state relay controlled with an Arduino Uno. When heat needs to be added, the Arduino outputs a high signal, which closes the relay and turns the heaters on. When no heat needs to be added, the Arduino outputs low, opening the relay and turning the heaters off. There is also an indicator light wired in parallel with the heaters that turns on and off with the heaters.
In lab, we turned the shock on and let the heaters run continuously to establish a baseline temperature response. A 5V power supply was used, rather than the Arduino, to send a signal to close the relay. It can be clearly seen in the temperature response plots below that the heaters drastically increase the heating rate of the shock. The heater and shock had to be turned off after about five minutes of continuous operation because the heater surface temperature reached 120°C, which is their maximum allowable temperature.In the future, we plan on adding a safety feature to the Arduino code that will turn the heaters off if their surface temperature exceeds 115°C. In order to do this, we will need to attach a thermocouple to the outside of the heaters.
In other news, The Hot Shocks received a prize for the 3rd best project proposal and presentation, as decided by out ME 107 classmates. We were rewarded with a Menchie’s gift card, which we used to fund a froyo party after this week’s lab session. Although we were disappointed that Eric could not attend the party, he would not have had fun anyway because he is lactose intolerant (boooooo!). Hopefully there will be more Hot Shock parties that Eric can attend in the near future. Next week is spring break, but hopefully we can hit the ground running with our hardware in two weeks and begin taking data with an operational control system.
Thanks for reading!
-The Hot Shocks
After assembling the heaters this week, we decided to take some data to get an idea of how quickly the heaters could increase the temperature of the system, and the results were pretty exciting! We found that after just 5 minutes, the shock had risen to 40C, which is 8 degrees greater than the predicted steady state of the shock running without a heater at 30RPM. This result tells us that the heaters we specified last week are more than sufficient to bring the shock up to the setpoint temperature of 90 degrees. It also tells us that the heaters will greatly reduce the time to reach our setpoint since the rate of temperature change over time is much higher with the heaters than without. This is very promising!
I tried to fit the small amount of data that we were able to collect this week, but unfortunately because we collected so few data points, it was challenging to fit a curve with much precision or accuracy; it predicted that the steady state temperature would be 1.05E5 degrees with a 95% confidence interval of ( -1.28E8,1.28E8). Obviously this must be very incorrect since that is significantly hotter than the sun, and our heaters are not quite that powerful. Hopefully next lab section we will have enough time after setting up the heaters to collect more data so we can better verify the heating system. Over break I will also be working on the mid semester lab report.
At Menchies I got mango frozen yogurt with strawberries and bananas! It was very tasty and I enjoyed it a lot. Yum yum yum.
When the heaters arrived at my apartment on Monday (just in time for lab!), I was excited to find that they were flexible enough to bend around the shock body, which had been a concern because of the published minimum bending radius of the heaters. During lab, I helped with the hardware setup of the heaters, thermocouples, solid state relay, and controllers. Now that the hardware setup is complete, I’m excited to connect the controller after spring break and start comparing the data to our models. Over break, my main concerns will be writing the mid-semester report and completing the Arduino code, which will use the output of the internal thermocouple to decide whether the heaters should be on or off.
At Menchie’s, I relished an eclectic mixture of Reese’s Peanut Butter Cup, Dulce de leche, and Peep’s Marshmallow Mania frozen yogurt, topped with coconut, granola, and mini brownies. This delicious treat, when combined with the companionship of my fellow Hot Shocks and the 3D puzzles we were given, may have made for my favorite froyo experience ever!
This week Eric and I implemented the hardware hysteresis controller. We first tested it on a breadboard before booking it up to the solid state relay connecting the heater to power. Using a potentiometer allowed us to simulate a temperature signal, and we verified that the Arduino registered the shock temperature switching above and below the reference temperature. We also verified that the Arduino was outputting a high or low signal to the heater of the shock temperature was below or above the reference temperature, respectively. We ran short of time this week and were not able to hook it up to the heater, but we plan on doing so next lab session. We will also code and verify the PID controller ahead of time so that we may tune it and then compare the performance of the two controllers using metrics such as rise time and temperature ripple.
This week I worked with my fellow Hot Shocks to set up and run initial tests to determine how our heaters function. With the help of Alex, we were able to set up the solid state relay and run the heaters with a continuous 5 volt input. We began the tests at 30 RPM and then ramped the shock to 90 RPM after five minutes. The heaters produced a smell that seemed like plastic burning. We initially thought this might be the zip ties, but after we finished testing and removed the heaters, the zip ties appeared to be in perfect condition. Since we were not sure what was causing the smell, Alex provided with an IR temperature measuring device. When placed on the heaters and the shock body in between, the measured temperature was close to 115C. We immediately shut off the shock to allow the system to cool down.
Over spring break I will be working on the Mid-Semester project report and implementing a safety control for the heaters to ensure they stay under the maximum temperature allowed by the product specification.
At Menchie’s, I enjoyed Coconut frozen yogurt topped with mini gummy bears, sour gummy worms, and mango popping boba.
This week I worked with Les on setting up our controller. We are using an Arduino UNO and a solid state relay. The arduino code for Les’s hysteresis controller works as expected. It worked in simulation and prior to using the actual hardware, we ran the controller and monitored the control input. The response was what we expected so next week we can fully begin testing. I am still refining the plant model and using parameter identification. Spencer has helped me a lot with the do’s and don’ts for parameter identification.
I was unable to attend the Hot Shocks party because I had class immediately after our lab section. It was probably for the best since I am lactose intolerant and the party was a froyo party.
I assisted Alex this week wiring up the hardware on the shock dyno and helped other members collect temperature data. In the coming weeks I plan to make a cleaner wiring harness for easier setup and takedown of our heating hardware.
At Menchie’s, I enjoyed a Reese’s Peanut Butter and Caramel frozen yogurt topped with Butterfingers, Andes Mints, Heath Bars and finished with Hershey’s Magic Chocolate Shell and Caramel sauce.