Hi LJHerfst, Welcome to EasyEDA. For help on stuff like this, you need to post some links to datasheets etc. for the BEE_MB's schematic and PCB design and to make your EasyEDA project public and then post a link to it, like this: [https://easyeda.com/LJHerfst/test-indoor-garden](https://easyeda.com/LJHerfst/test-indoor-garden) A description of what the circuit is for and how it works would be good too. Otherwise no-one can see what you are talking about and it is unfair to expect other people to do all the searching and looking up that you have clearly already done just to find the relevant documentation and to comprehend your project. The input connections to the Power Supply section do not make sense. * What is the polarity of these inputs? * Why are there two input voltages apparently both of 12V but which do not appear to comprise a +/-12V supply? * How is the 12VPP supply related to the 12VIN supply when they have no ground connedction between them? * Why is there a fuse in the ground side of the 12VIN supply input? * There is no supply decoupling local to U5. See: [https://easyeda\.com/andyfierman/Power\_supply\_decoupling\_and\_why\_it\_matters\_\-451e18a0d36b4f208394b2a2ff7642c9](https://easyeda.com/andyfierman/Power_supply_decoupling_and_why_it_matters_-451e18a0d36b4f208394b2a2ff7642c9) * What loads is this circuit intended to drive? (Type, Voltages, Currents?) * Please note that the parallel LED3 - LED6 drive in the **Sensors** section of this design is poorly implemented. To understand why, please see: [https://easyeda\.com/andyfierman/LEDs\_must\_have\_series\_resistors\-OoGYgCK2k](https://easyeda.com/andyfierman/LEDs_must_have_series_resistors-OoGYgCK2k) * To get the best out of your journey into electronics in general and EasyEDA in particular, please see: [https://easyeda\.com/andyfierman/Welcome\_to\_EasyEDA\-31e1288f882e49e582699b8eb7fe9b1f](https://easyeda.com/andyfierman/Welcome_to_EasyEDA-31e1288f882e49e582699b8eb7fe9b1f)

@andyfierman Thank you very much for your reply, which is very helpful.  This and next posts I'll  include the links to the project in question: [https://easyeda.com/LJHerfst/test-indoor-garden](https://easyeda.com/LJHerfst/test-indoor-garden) . This project is based on the project of BEE_MB: [https://easyeda\.com/BEE\_MB/Indoor\_Garden\-fd51aadca2f24976b6d9bf39da94931f](https://easyeda.com/BEE_MB/Indoor_Garden-fd51aadca2f24976b6d9bf39da94931f).  I've read the tips and see that quite a few things need to be changed in the original design. For example, fuses should be at the high voltage side I assume? I assume BEE_MB included 2 power supplies for distinguishing between those modules requiring relatively low power (Arduino, HC-06, ESP-01) from those that require higher power (fan, lighting, pump). For the LED drives I will make another circuit. After reading your comments I have a few questions remaining: 1: If 12 VPP and 12 Vin DC power supplies have GND connected to each other than NetPort "VPN" is not required anymore? 2: In the Indoor Garden Schematic I see that the IRF540 for the pump control is connected in a different way to the VPN port  (IRF540 PAD #3) as compared to the other 2 (fan&light brightness, VPN connected to PADs #2). Is that correct or should I change it? 3: I've seen other schematics that use a voltage divider (1k /2k resistors) between the TX pin of the arduino nano and the bluetooth hc-06 module RXD pin. Such voltage divider wiring has been used between ESP-RXD pin (nano) and RXD pin from the ESP-01 Module but not between TX pin nano and RXD pin HC-06. Is that correct? Won't it damage the HC-06 long-term? 4: Regarding the RXD and TXD connections I see that ESP-TXD (nano)  wires to TXD (ESP-01) whereas TXD (nano) wires to RXD (HC-06). I'm not familiar regarding the RXD TXD communication protocols. Why this TXD-TXD TXD-RXD difference? Is that correct as well?

Sorry but as I have already tried to explain, your questions cannot be answered without you first answering the questions I asked you. The links you have posted do not give any of this information. _You_ may know what this collection of bits and connectors is for and how it is supposed to work. Please do not assume that anyone else does.

@andyfierman, I'm sorry about the confusion To be honest, I don't have a very clear view about 'what the collection of bits and connectors is for', but I'll answer your previous questions first: * What is the polarity of these inputs? * \> The board has 2 12V DC inputs\. A \+12 V input and a GND at 0V\.  * Why are there two input voltages apparently both of 12V but which do not appear to comprise a +/-12V supply?  * How is the 12VPP supply related to the 12VIN supply when they have no ground connedction between them? * \>  I assume BEE\_MB included 2 power supplies\, both \+12V for distinguishing between those modules requiring relatively low power \(Arduino\, HC\-06\, ESP\-01\) from those that require higher power \(fan\, lighting\, pump\)\. I guess the grounds should be connected\. So\, 2 motor outputs \(fan\, pump\) and 1 output that require preferably a constant current supply of a few hundred  mA \(power LEDs\) * Why is there a fuse in the ground side of the 12VIN supply input? * It should be on the +12V side I guess. * There is no supply decoupling local to U5. * I don't know how these capacitors (?) should be arranged. At this stage, your discussion about power supply decoupling is rather complicated for me. At what part of my schematic would this power supply decoupling be needed, to suppress 'rail transients'?

I suggest, rather than asking someone else to try to analyse and understand this circuit, why not try to contact the original designer? You may be able to contact them using the EasyEDA messaging feature.

Well, you're completely right. At first I contacted the designer via easyeda's private message option a bit more than a week ago. He hasn't answered yet, so I'll try to contact him another way. I thought perhaps other people might have some thoughts about it independently, so as a second option the forum might be very helpful.

The problem is that there is no documentation for the project and the schematic is poorly documented so it is very difficult to offer any kind of meaningful help. Without knowing even what and exactly how the power supplies are connected, it would be dangerous to try to second guess the originator's intentions. You are also assuming that the design as presented by the originator actually works. This may not be a valid assumption.