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I have a problem with the project I am currently working on: https://git.la10cy.net/DeltaLima/CanGrow/

I designed and ordererd a PCB for it and tried the schematics on a perfboard beforehand. But without the extra LM/AMS1117 shown in the schematics, because as I was developing software until the PCB arrived, I did not needed it, because its connected by USB anyway. Everything was working fine with the esp powered by USB.

With the todays delivered PCB (v0.4 of the design, https://git.la10cy.net/DeltaLima/CanGrow/src/tag/v0.4, schematics in KiCad folder as pdf), I used the LM1117 for powering the ESP (I used https://de.aliexpress.com/item/1005004704507586.html?) and applied 12 V to "12 V input", without the USB connected and the esp got fried when I powered it up. I checked beforehand for shorts, and checked the voltages without the esp in the socket, and everything looked good.

I am pretty confused and cannot explain what is going on here. I am an electronics hobbyist and have just a basic set of knowledge.

Also i tried then, to prevent further damage, the circuit with a regulated power supplay and capped it to 200 mA. When I plug in the board without the esp it draws about 5 mA. When I then plug in the ESP, it looks like a short and CC regulation kicks in from the power supply and the voltage drops down on "12V input". It was a brand new esp and i checked it for functionality beforehand. When I leave the LM1117 out of the schematics and power the ESP by USB, everything is fine.

Am I am missing something in my circuit? I thought that I have not used pull down resistors for the BC547 base which is connected to the esp digital pins D0, D5, D6. I am afraid to test around further, because I fried in sum two ESP's investigating this problem and I don't want to kill another one and produce ewaste.

I am appreciating every help!

Best regards and thanks,

Marcus / DeltaLima

Edit: schematics of my project as PNG attached to the thread: cangrow v0.4 schematics

Edit2: Picture of the AMS1117 Module i used, with capacitors soldered on it

Picture of the AMS1117 Module i used, with capacitors soldered on it

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  • \$\begingroup\$ It's not your main problem but the gate driver circuits for the N channel mosfets appear unnecessarily elaborate. \$\endgroup\$
    – 6v6gt
    Commented Apr 20 at 4:36
  • \$\begingroup\$ The circuit needs to be posted as an image to future proof your question. \$\endgroup\$
    – Andy aka
    Commented Apr 20 at 9:04
  • \$\begingroup\$ @6v6gt what would your suggestion for a driver circuit? i thought i pick up the one with the least different components. I got it from here en.wikipedia.org/wiki/File:MOSFET_Driver_Circuit.jpg \$\endgroup\$
    – DeltaLima
    Commented Apr 20 at 12:10
  • \$\begingroup\$ @Andyaka i uploaded the schematics to the first post :) \$\endgroup\$
    – DeltaLima
    Commented Apr 20 at 12:10
  • \$\begingroup\$ @DeltaLima I'll just summarise the driver options because this is really a topic on its own. With a suitable logic level (3.3v) N channel mosfet you could drop both npn transistors. With a P channel mosfet (replacing the N channel one) you could drop one npn transistor. If you invert the logic (Arduino/ESP pin HIGH = off) you could drop one npn transistor. With an optocoupler you could drop both npn transistors. Incidentally, with those inductive loads (fan, pump) there should be a flyback diode across them. \$\endgroup\$
    – 6v6gt
    Commented Apr 21 at 2:28

3 Answers 3

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So I think I got it solved with your help.

I used now an mini-360 DC-DC buck converter board for the 3.3V rail which powers the ESP8266. With this module everything just works fine. No weird voltage drops, no shorts, no smoke - it just works as expected.

From what I have seen and learned in other forum posts or videos, like these two to:

I really missed the in- and more importantly, the output capaciter. It seems the ESP8266 has a quite high current draw at start up to 350mA which the AMS1117 , even the module with the caps on it, cant handle and break. As I understood those current Spikes can buffered by 1000-2200µF capacitors. but then still the AMS1117 would loose quite a lot of power in heat which the mini-360 buck converter doesnt.

So i will now go the safe route and invest few cents more and take the mini-360 which can also be made "pin compatible" with the AMS1117/LM1117 :)

Thanks to all your help and input! <3

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The common reason for the rapid burnout of "LM/AMS1117" is that its positive and negative pins are reversed. You can add a regular diode in series to its positive pin to prevent this from happening. The voltage drop on the added diode will not affect the operation of "LM/AMS1117", but it may affect the operation of other components, so do not place it elsewhere.

ps: If you simply draw a wiring diagram for your 'LM/AMS1117', it may help everyone quickly identify the problem.

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  • \$\begingroup\$ Thanks for you answer! I added the schematics in my first posting as picture :) I double checked polarity of the AMS1117 and it was correct. I also used in the first place those linked ams1117 modules which came with the capacitors soldered to the module. :) \$\endgroup\$
    – DeltaLima
    Commented Apr 20 at 12:01
  • \$\begingroup\$ I noticed that when I tried to prevent further damage, I used a regulated power supply and capped it to 200 mA. When I plug in the board without the ESP, it draws about 5 mA. When I then plug in the ESP, it looks like a short and CC regulation kicks in from the power supply, and the voltage drops down on the '12V input'. It was a brand new ESP, and I checked its functionality beforehand. When I leave the LM1117 out of the schematics and power the ESP by USB, everything is fine. \$\endgroup\$
    – Sam.Ma
    Commented Apr 21 at 3:54
  • \$\begingroup\$ This means that the ESP's power consumption is quite high. In this case, the LM1117 chip will be internally short-circuited and destroyed, causing the 12V to be directly applied to the ESP, which will cause it to burn out. Since the LM1117 is designed for low-power scenarios, it does not have the capability to handle high loads. I recommend using a 'DC/DC' type power converter, such as the 'K78L03-500R3' or the higher-power 'K7803MT-1000R4' from Mornsun, which have sufficient current output to meet the ESP's needs. \$\endgroup\$
    – Sam.Ma
    Commented Apr 21 at 3:55
  • \$\begingroup\$ Additionally, to ensure the safety of your circuit, you can test the output voltage of the power module before installation by connecting a small-value high-power resistor (connected in series as a dummy load between the power supply and ground) to check if the output voltage is normal and meets your requirements. Note that this resistor will be extremely hot and may even catch fire, so please be careful to avoid burns and fires. The resistance value = voltage / current, i.e., 3.3V divided by the maximum current required by your ESP." \$\endgroup\$
    – Sam.Ma
    Commented Apr 21 at 3:55
  • \$\begingroup\$ As I read so far too, I think the idea to use an ams1117 to regulate 12V -> 3.3V is not the best, electronics.stackexchange.com/a/642346/370604 I guess I will try to go with another solution, like an 7805 connected to 12V to power the ESP D1 with 5V on it's 5V pin. \$\endgroup\$
    – DeltaLima
    Commented Apr 21 at 15:55
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There is no input capacitor and no output capacitor around the linear regulator LM1117 on board.

The datasheet suggests 10 µF at the input and 100 µF at the output in the example schematics with one exception, that uses a 10 µF Tantalum capacitor at the output.

Without these capacitors the regulator tends to oscillate and cannot establish proper regulation. Without the ESP module this is not critical and you might measure the correct output voltage.

It is not safe to rely on the internal capacitor of the ESP module. This is not close enough to the regulator output and the value is too small.

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  • \$\begingroup\$ thanks for your answer! In the latest design of my project i added 10µF electrolyt capacitor to ams1117 in- and output. :) I really thought the modules one would be enough. Good to know it's not :) \$\endgroup\$
    – DeltaLima
    Commented Apr 20 at 12:12
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    \$\begingroup\$ The module has regulator with caps. The schematic component is not the regulator but module. \$\endgroup\$
    – Justme
    Commented Apr 20 at 13:27
  • \$\begingroup\$ @DeltaLima There is a risk to insert the regulator module in the wrong direction. \$\endgroup\$
    – Jens
    Commented Apr 20 at 15:58

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