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I'm 14 years old and I am building a hotplate and would like some suggestions for improving the circuit to be more efficient and safer. I have already improved the 12-30V to 5V voltage regulator/DC-DC converter from this question and I have improved other things from this question. The hotplate would be external and it has 2 GND (that's why there are 2 "HeatingElement-" outputs). There will also be a front panel with 2 buttons, a display and a buzzer that will all connect from the pads. Also, for the 5V possibly backfiring into the USB when 12V is plugged, what can I do to solve this?

Schematics:

Schematics

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  • \$\begingroup\$ Find proper connector symbols, especially the FTDI block is unreadable. The heating element one doesn't look good either. And the front controller one takes some prime real-estate on your schematic for something that's logically "unimportant". \$\endgroup\$
    – Mat
    Commented Feb 17 at 6:16
  • \$\begingroup\$ Be careful with the power supplies. We don't know what are intentional desicions and what are mistakes. Can you explain what this should do in order to comment if it is made correctly or not. How should each thing work in different scenarios or can we ignore some scenarios? Is it e.g. OK if it blows up your computer if you plug a PC to USB-C while 12V is fed in from external supply? Also, why a MC34063A, the part has to be twice as old as you, while modern parts which can work with less and smaller external components. \$\endgroup\$
    – Justme
    Commented Feb 17 at 10:32
  • \$\begingroup\$ For the MC34063A, I've been told that it works easily enough so thats why I took IT. And for the 5v backfiring into the USB , what can I do to solve this? \$\endgroup\$ Commented Feb 17 at 15:17

2 Answers 2

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You have made good improvements based on your questions.

My suggestion is to take a step back and look at simplifying your architecture.

Try to solve 1 problem at each iteration. Having multiple non-trivial circuits in a new design can be really tough to debug and isolate what is causing the problem you are seeing. Sometimes that can't be avoided, but my experience is avoid it if you can at all.

I see your first level problem to solve is to control the hotplate temperature.

For a first generation solution to your design, take a look at a DC-DC module such as the Cui P78E05 to replace your 12V-35V to 5V circuit. See if you can find a ESP32 board with 5V Vin - it has the 5V->3.3V regulator on board. I like using the XIAO-ESP32 board, but it doesn't have enough I/O for your design so I don't have a board to suggest for you.

Once that is working well, add the more elegant solutions. For a buck converter, I'd suggest looking at solutions based on newer ICs. The solution size and electrical performance will be significantly better.

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The 5V addressable LEDs generally do not work with 3.3V data bus from MCU. You need a level shifter to convert a 3.3V high speed data signal to 5V.

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  • \$\begingroup\$ In an other circuit, I was using the Led with 3.3V and they were working fine. I changed them to 5V only after somebody said me they would work better. So should I still put a level shifter?? \$\endgroup\$ Commented Feb 17 at 15:12
  • \$\begingroup\$ @LoicDaigle There are things that must be done right so they always work correctly. Otherwise, you make a circuit that might work or might not or might work 50% of the time correctly. If your friend makes a copy of your circuit, the friend may have a MCU/LED combination that never works, and all you can say that you made one and it works for you. If you make 10, one might work and 9 not. The Internet is filled with circuits that barely work or might not work at all. \$\endgroup\$
    – Justme
    Commented Feb 17 at 15:19
  • \$\begingroup\$ So I should still put a level shifter? And can somebody explain me how it works? \$\endgroup\$ Commented Feb 17 at 15:22
  • \$\begingroup\$ @LoicDaigle Yes, like I said, you should put a level shifter. How it works is another separate question, because I don't know which level shifter you are going to use. And if you want to ask which you should use, given the context of using 5V addressable LEDs with a 3.3V MCU, it has been asked here many times in many points of view so do a search . \$\endgroup\$
    – Justme
    Commented Feb 17 at 15:26

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