Hi all,
I’m quite new to PCB design so please bear with me.
Attached is my schematic below and the error I receive when I run ERC check. I’m not sure what is causing it.
I am assuming I just fundamentally misunderstand how the PWR_FLAG works? When I place the PWR_FLAG on the V0 pin of my 3.3V LDO, it complains about power output to power output. From my understanding, the PWR_FLAG is telling KiCad that a specific voltage label’s power comes from the flag and not to worry about it. That makes sense then why I would get that error. What I don’t understand is why the +3V3 power input is not being driven/detected.
Also, if there are any general schematic comments or anyone would like to look over my logic further that would be very much appreciated. The idea is to create a modular sensor board (plug and play sensors are the goal) using an ESP32, powered from a 24V input, stepped down to 5V with a buck converter and then to 3.3V. Think along the lines of a 3d printer environment monitor, but more so for assembly line machines. Data transmission will be over LoRa.
I’m not sure of this sentence meaning (why there are two possibilities: driven or detected).
Your U1 3V3 pin is defined as Power Input and there is no power output at the net it is connected to.
There are also only 2 capacitor pins at this net and no one of them is a power output.
Well, pardon me saying so, but your schematic is a big mess. You’re mingling GND symbols and labels. put labels on top of wires or so close to symbols that they overlap with pin numbers. You also mention the PWR_FLAG in your text, but I don’t see it in your schematic.
But for the solution to the title of this post. I suggest you blink your eyes, get some coffee and then look at the excerpt of your screenshot below until you spot the error yourself.
Also, as an unrelated advise, it’s common to omit “Ohm” and “F” for Farad units in schematics. (That greek Ohm symbol is too hard to type anyway). It’s more common to use RKM_code
You have very small electronic understanding or a translation problems.
U1 3V3 pin is defined as Power Input because probably it have to be powered by some external source. Even I don’t know ESP32 I don’t think this pin can output 3V no matter how much you want it.
Yea I messed up the terminology. I meant to ask how do I create a power output at the net it is connected to? I use the power input symbol for +3V3, how do I avoid drawing wires everywhere on my schematic and have the same sort of labelling idea?
Is general convention to use GND symbols for everything? I used one GND symbol and then everything else was a label because I was under the impression you had to define what GND was first before using the labels.
Oops, Indeed 3 PWR_FLAGS. Two in the upper left corner, and the third more to the right. I also had to search a bit for the connector where 24V enters the schematic, before I realized it was also in the upper left corner, but drawn “backwards”.
For OP: there are simple conventions that make schematics easier to read, and make errors easier to spot. Signals flow from left to right, and voltages from top to bottom. For example, drawing R2 “upward” to GND makes it hard to see it’s function as a feedback for the SMPS. I also tend to put PWR_FLAG symbols close to where the actual output is. So for the VCC_5V net, it would not be on the feedback resistor R1, but on the inductor L1.
You are also using too much labels. Just now I spotted that D1 is also connected wrongly. It should be connected to VCC_5V_Buck_RAW instead of VCC_5V.
GND is a very important net in each electronic circuit, and normally the GND symbol is used for all GND connections, and labels are not used for GND. For the computer it does not matter much. Internally all power symbols create nets with global net names (labels).
Have you spotted your error yet in the excerpt of your screenpost I re-posted? (Hint: Capacitors don’t conduct DC current).
I thought you were pointing me in the direction of the power input symbol. I was under the impression I had to decouple the power input so I added both capacitors to filter out low and high frequency noise.
Drink more coffee, stare harder. But before you do that, first put some cushions on the wall, because when you finally spot your mistake it will be a real headbanger.
Yes, decoupling capacitors are between GND and the power supply, but apart from the capacitors, the 3V3 pin of your ESP32 is not even connected to the +3V3 power supply at all.
Considering that you have not only so many blemishes (which in Finnish we would call “beauty mistakes”) but also functional errors in the schematic, I doubt if you can do the layout any better. Most of the capacitors here lose their purpose and effectiveness if they aren’t positioned and routed properly, and the same goes for the TVS diodes. Good GND plane is critical, too. Piotr can give you a link to a thread which has advice for capacitors (the whole thread is worth reading) and Paul is famous for his link to a professional video about GND layout. Don’t proceed before you have understood these basic things.
