In this session I worked on the XL4016 circuit and implemented it, choosing the correct replacement parts for ones that aren’t available locally in my country. Then I tried my best to implement current limiting, but it was too hard for me because I don’t understand enough about electronics to implement it. So I will try another time.
I started this session by researching which cooling fan to use, by its voltage, current, and size. I chose a 120mm 24V fan so it’s big enough and can take voltage directly from the input 24V rail instead of needing to have an extra 12V rail to power the fan. This also keeps the fan’s current input low, so it leaves more current for the power supply to output. Then I wanted to add more protection features, but I found that most schematics online were too complicated for me to understand, so I decided to delay this for later, and now I will implement the main buck converter that will generate the power supply’s output. I spent a lot of time trying to find a buck converter IC which is switching, has high current limit, a wide range of output voltage, and is available locally in my country. This took a lot of time, and reading lots of datasheets, but in the end I decided to use the LT1074CT. However, after wiring the LT1074CT circuit, I discovered that it’s minimum output voltage is only 2.21V, which is very bad for my power supply, because I won’t be able to set 1.5V or 1.8V, which are very common voltages in electronics. I could’ve solved this by two ways, firstly I could’ve added a linear regulator after the LT1074CT’s output which can step the voltage down to lower than 2.21V, but this is too complex, so I decided that I will replace the LT1074CT with XL4016E1, which is very similar to it but has a more practical voltage output range of 1.25V to 32V instead of 2.21V to 40V. It also has a higher current capability, 8-12A, instead of 5A, which will be very useful in the future if I plan to use a higher current power supply, e.g. for electroplating large 3D prints. And finally, the XL4016E1 is a more common regulator, so it has more online documentation.
In this short session I did research on which temperature sensor to use and decided to use the DS18B20.
I started planning the schematic and features, and choosing components according to local availability. I wired the input voltage circuit and a step down circuit for the ATmega328P, which will control the power supply logic. Then, I made the essentials of the ATmega circuit, which is, the decoupling capacitors, the LC circuit for AVcc, the reset circuit, and the crystal circuit.
