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I'm a beginner when it comes to PCB design and I'm looking for design feedback for my schematic which I've created in KiCad.

The idea is straightforward: I want to individually control 4 DC motors using 2 L298N IC's, which will receive their logic from an ESP32 Node MCU.

Here's the schematic:

enter image description here

I want to make sure that there aren't any obvious issues I'm overlooking like the lack of a decoupling capacitor for instance.

random_coder_101
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    You might want to check out this: [Problems with L293, L298 and SN754410 H-bridge drivers on a low voltage supply](https://electronics.stackexchange.com/questions/108686/problems-with-l293-l298-and-sn754410-h-bridge-drivers-on-a-low-voltage-supply). – Andy aka Sep 02 '22 at 13:46
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    Will your uC be happy with a 1V voltage drop due to D17? – Chris Knudsen Sep 02 '22 at 14:03
  • You should separate your grounds. You don't want motor current flowing past the CPU to the extent you can avoid it. Make a 'motor gnd' in addition to your existing 'gnd', and physically connect them at the power input only. You can force Altium to respect this separation by using a zero-ohm resistor to separate the two. – Kyle B Sep 02 '22 at 15:39
  • Looks fairly neat. I would flag +5V as power so ERC doesn't throw a fit. I would also check to see how happy your controllers will be getting power but no inputs. – vir Sep 02 '22 at 17:10
  • @ChrisKnudsen - Fair point. The ESP32S Node MCU requires about +5V, so after the diode will have somewhere around 4.1-4.2V which I'm guessing should be enough for most activities of the MCU. Would you recommend that I switch out the AMS1117 to something that gives out higher than 5V? Or do you think its safe to get rid of the diode to avoid voltage drop? – random_coder_101 Sep 02 '22 at 18:25
  • @vir - Do you mean connect +5V to a PWR_FLAG and then use that instead of the +5V Power net I'm currently using? Sorry, didn't quite understand that. My remaining issues with ERC are all centered around the L298N schematic which I'm using from the KiCad library so I'm choosing to ignore those cause it's mostly around input & output pins, which isn't a big concern. – random_coder_101 Sep 02 '22 at 18:28
  • If your +5V_Power net isn't defined as power, ERC might throw an error because the L298 is expecting power on VSS. Depending on how you drive your motors and how big they are, the sag on your 5V rail might reset the ESP32, especially since I don't see local decoupling there. – vir Sep 02 '22 at 19:04
  • @vir - So, I've run an ERC check and KiCad doesn't complain about the lack of power to V_SS, so I'm assuming what I've provided is fine. Regarding the ESP32 being reset, what is the workaround for that? where do I provide the decoupling capacitor to avoid this? – random_coder_101 Sep 02 '22 at 21:05
  • Looking at the schematic of the ESP32, it looks like they have an onboard 100nF capacitor so you actually should be good there. – vir Sep 02 '22 at 21:19
  • RE D17: Ask yourself "what is the role of this diode?" Typically in this style of circuit, overvoltage/reverse voltage protection is centered around the voltage regulator. Reverse input voltage, your likely intent for D17, is better handled on the input of the regulator where you will likely have a voltage overhead already (like Vin=9-16V, or something). Placing a series diode there has little impact (regulator headroom requirements for Vin= 1Vdiode+Vdropout of the regulator). Make sure the series diode has the proper power dissipation requirements for the 5V rail of your entire circuit. – Chris Knudsen Sep 06 '22 at 12:37
  • @KyleB - How do I separate the grounds for the motor and the CPU in KiCad? – random_coder_101 Sep 10 '22 at 07:32

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