We figured that the reason why the oven’s not working at 100% is due to the diode. As we explained earlier, before the power going to the heating elements it has to go through the diode which converts the AC power into DC. Using the digital multimeter, we measured that the voltage before the diode is around 117V, but after passing through the diode it drops down to only 64V. Therefore, we conclude that the diode is the main reason why the oven’s not functioning at 100%. This probably has to do with the oven’s initial design as the diode is only used when the oven is switched into certain mode.
Digital Multimeter
Hence, we decided to cut off the diode and rewire the oven again. This new circuitry is basically the same as it was before, it the two upper heating elements parallel with the two lower heating elements, except that this time there will be no diode in the circuit. The new circuitry looks as below:
New circuitry
After that, to make sure that the oven will perform differently and more efficiently, we made another test, similar to those tests that we had before. Therefore, with the RoastLogger program, we got the following new graphs:
New graph: No diode connected
It’s easy to notice how much more efficient the oven is working. With the heating elements turned on at 100%, it was able to reach the temperature of 380F in about 4 minutes, which is only slightly less than what we need for our temperature profile. Nevertheless, this small difference is manageable as we have some certain methods to improve the performance of our oven. Now we know that our oven is working the way we want, the next step is to test the PID controller from the RoastLogger program to see if we can manually control the temperature within the oven or not.
