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Message ID: 90     Entry time: Tue Oct 4 22:15:23 2022
Author: Jennifer Hritz 
Type: General 
Category: Optical Contacting 
Subject: Hot plate PWM Test #1 

I wrote a program to control the heating rate of the hot plate using Pulse Width Modulation (PWM), and it was a great success!

For roughly 6 minutes, the hot plate was power cycled with a rate of 100 ms on followed by 900 ms off. Based on my calculations, this should correspond to a 0.08°C/sec temperature increase. In other terms, we expect a 24°C increase in the span of 5 minutes. For comparision, without PWM, the hot plate heats up roughly 100°C in that same timespan. I recorded the temperature by filming a thermometer and transcribing that video into a text file, which could be analyzed and graphed. I only transcribed the first 5 minutes of the 17 minute video (I also filmed part of the cool down) because 5 minutes was enough to show clear results.

At t=0, the hot plate was 21.4°C, and at t=300, the hot plate was 49.7°C. That is a 28.3°C increase in the span of 5 minutes, only 4.3°C higher than the predicted value. The rate, 0.094°C/sec, is only slightly faster than the desired 0.08°C/sec. Further, as shown in the graph, the temperature increase was almost perfectly linear, which is ideal. Overall, using an Arduino to PWM the hot plate is looking very promising.

Attachment 1: PWM_Test_#1_(first_300_sec).pdf  11 kB  Uploaded Wed Oct 5 02:03:37 2022  | Hide | Hide all
Attachment 2: frame_from_pwm_test1_video_PXL_20221005_064240498_exported_231444.jpg  288 kB  Uploaded Wed Oct 5 02:04:03 2022  | Hide | Hide all
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