PC does not recognize the USB serial port after some days

[A_neves]

- I don't think that will cause problems in your design.

To me, an all plane to current supply seems to be the best solution. I think that on this way we make a strong connection. But on that post, seems to be the opposite.
​But robertferanec, do you think that place vias next to +VCC and GND decoupling capacitors is the best way to connect them?
I am testing my board with 2 ferrite core on USB cable and 2 on my AC / DC External Plug In Adaptor 12V and seems to be ok now.

Thank you!

[robertferanec]

do you think that place vias next to +VCC and GND decoupling capacitors is the best way to connect them?

- in very high density designs, I place VIAs where the space is and everything is working ok. Of course there are better and worse ways to place VIAs to connect decoupling capacitors, but I do not think in your board as you have it on the picture you need to worry about that.

I am testing my board with 2 ferrite core on USB cable and 2 on my AC / DC External Plug In Adaptor 12V and seems to be ok now.

- That is a great news!

[A_neves]

robertferanec I am testing a new design of PCB. At this moment the system never lost the connection even without the ferrite coil on USB cable and power adapter.
Do you think that the new design could make all the difference?

Thank you!

[robertferanec]

Yes, good layout makes big difference in reliability. But keep testing.
PS: I see, that you improved USB layout.

[A_neves]

robertferanec yes, I am testing. But the problem is I need to produce very soon 30 PCBs and I do not know until when I should test to assume the problem was solved.

Thank You!

[A_neves]

robertferanec the problem shows up again.
I am working with solenoids to open a door. To activate the solenoids I am using a mosfet with a flyback diode to protect my circuit.
I am using a 230AC to 12DC power supply to supply my circuit. Could be some noise on my power that change my GND reference?

Thank You!

[ypkdani]

Hello,

why did you put varistors for protect the USB? For usb you need to use ESD diodes because they have capacitance of 10-50pF instead 100-1000pF. Could be that components that degrade the signals?

[A_neves]

Hello ypkdani ,

At the beginning I used varistors because I followed arduino uno schematic.
Now I am using TVS diodes (PGB1010603NRHF) and a 47pF capacitors on D+ and D-.
I thought that the problem was solved. But yesterday, my office had a building works and the lights start to blink for a while. The air conditioner also stopped, started, stopped and started for a few seconds.
This make my circuit have this failure, even with an UPS on AC to 12VDC power adapter and the PC.

So I am thinking that the problem could be on my supply.
I am also using ferrites cores on USB cable and my AC to 12VDC power supply.

Thank you!

[robertferanec]

230V is not may area, but if you are turning it on / off that can generate peaks which could disturb some circuits. I forgot, is your circuit powered through a real transformer (galvanic separated) or is it powered through a switching power supply (which is not galvanic separated from main power). That could maybe help a little bit - at least I would try it. Also, is it in metal box, are you using EARTH / CHASSIS ground, etc .... all this can have influence.

[A_neves]

robertferanec this is the power adapter that I am using:

http://www.farnell.com/datasheets/2547969.pdf?_ga=2.161821820.1970858869.1573914190-1337627251.1568183825&_gac=1.226448744.1573914190.Cj0KCQiA2b7uBRDsARIsAEE9XpHSBA1Aj8okCTQR1koYYEVXp0tLllAyCtNIpbFCaPNQlQlVydeybpYaAuUiEALw_wcB

On my 12VDC input connector, I am using a mosfet PNP to not allow inverce polaraty voltage.
After that, I am using some capacitors to have sure that when I activate my 12VDC solenoid through a mosfet, I do not have a voltage drop.
Next point after this capacitors is 12VDC to supply solenoids and 12VDC to supply DC/DC to 5VDC that supply the digital circuit (microcontroller, FT2232D and sensors).
I am also using 2 long cables that supply a 5VDC sensor and a uart cable. This cables are shielded and cross wired and have 330 cm.
Could this also give also a problem?

Thank you!

[robertferanec]

this is the power adapter that I am using:
http://www.farnell.com/datasheets/25...YaAuUiEALw_wcB

Try to measure if GND on the power output is connected with EARTH pin of the input. I guess, it is. Maybe what you could try is find a real transformer power supply (no direct connection between input / output). I have seen some cases when that helped.

[A_neves]

Try to measure if GND on the power output is connected with EARTH pin of the input.

Should not have this connection between EARTH and GND? Could you talk a little more why is this a problem?
How can I have sure that there is no connection between them when searching on farnell or digikey?

I am realy woried about that, because the PC and cameras on the PC stil working with no any problem, only on my board.

Thank you!

[robertferanec]

Should not have this connection between EARTH and GND? Could you talk a little more why is this a problem?

- in some cases using transformer helps (separating your circuit galavanically from main power helps) because it prevents flowing currents and transferring noises through grounds between your device and Mains. Basically, this is what happen:

This is very simple explanation (doesn't include situations when you need to ground enclosure):


Option 1)
o--------- SWITCHING POWER SUPPLY ---------o Your circuit connected to MAIN ground
230V
o-------------------------------------------------------------o Your circuit connected to MAIN ground


Option 2)
o--------- TRANSFORMER ---------o Your circuit separated from MAIN
230V
o--------- TRANSFORMER ---------o Your circuit separated from MAIN

How can I have sure that there is no connection between them when searching on farnell or digikey?

- I am not sure, they should probably say that (also, they are usually bigger than switching power supplies for same rating)

But it is only something what I would test, I am not sure if that will solve the problem.

[A_neves]

Hello all,

I made some tests. The GND output of my 230 VAC to 12VDC Power Supply it is not connected to EARTH pin of the input.
I am using nettie to connect all the GNDs (GND of my AC/DC power supply and GND of digital circuit). When I measuring it, I find out that there is some noise and I think that when there other machines on AC line induces fluctuations on my GNDs.
How could I filter the output of my AC/DC power supply properly and limit the current to prevent a peak when a solenoid is activated?

I am also thinking to use optocouplers on my 2 UART lines and supply the FT2232D from VUSB to use independent supply sources.
What kind of optocouplers could I use?

Thank you!

[robertferanec]

The GND output of my 230 VAC to 12VDC Power Supply it is not connected to EARTH pin of the input.

Hmm, interesting. All this kind of power supplies usually have it connected together.

I do not know how to help more.