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Thread: Project "PCB" review service / advice?

  1. #1

    Project "PCB" review service / advice?

    I am putting together a timer project that use a Teensy 4.1, GPS chip, a couple of DC-DC converters, Lora module, Bluetooth module, RS485 module, thermal printer, WS2812 LEDs, Nextion screen, keypad etc... You may have already noted that I am talking about modules - yes, these are largely discrete subassemblies but I have designed a PCB with EasyEDA to make them easy to connect and added a few things that are at the edge of my electronics comfort zone like protection diodes, voltage divider for voltage monitoring, external pullups for some inputs etc however I'm at the point where there are some things I suspect I just don't know how to add.

    - Undervolt lockout of even trying to power up the 9V printer (if powered on by USB)
    - optoisolated inputs for the timing beam inputs
    - proper ground plane (I don't know anything about it)
    - Correct choice of pullup/down resistors for inputs - how can I make the inputs less susceptible to phantom inputs that I think I am seeing (2 HW pin interrupts fire OCCASIONALLY when only one of the buttons is pressed etc).

    Rather than try to solve all of these myself, I wondered if there are people or services that could review my design in EasyEDA directly for clangers of mistakes? I'm not expecting this to be free!!!

    If anyone is aware of such a service, I'd love to hear about experiences, or if this is even a reasonable request given the reviewer may not be away of the full functional requirements.

    I have attached a pic of the board (working fine except for very occasional phantom inputs) to give an idea of complexity.

    Cheers - NeilG
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  2. #2
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    You could try the EEVBlog forum.

  3. #3
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    Quote Originally Posted by UHF View Post
    You could try the EEVBlog forum.
    Yes, you will get some decent feedback. Just have a thick skin and ignore the inevitable "you're doing it all wrong" comments. I have always found it worth asking questions there even thought the SNR can reach 1:10.

  4. #4
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    Yes, usually it's a day of good feedback and then they start disagreeing with each other. Try asking if the shield on a USB connector should be grounded... This forum seems exceptional by contrast.

  5. #5
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    Adopt "fill all unused areas", usually with ground. It performs better and the PCB production is "greener".

  6. #6
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    Quote Originally Posted by jonr View Post
    Adopt "fill all unused areas", usually with ground. It performs better and the PCB production is "greener".
    @jonr: Thanks for that tidbit !! Do you do this on both sides of a 2-layer PCB & they are thus connected to each other ??

    Mark J Culross
    KD5RXT

  7. #7
    Thanks gents - good thought! I'll do that this evening. I am fully prepared for the "you're doing it all wrong" because I genuinely think I am. I know _NOTHING_ about PCB layout or circuit design. I have used the PCBs as a compact way to join together modules so I don't have jumper wires going everywhere! :-)

    However now I am using a PCB it would make sense to put a few things that I think I need directly onto the board. I am comfortable with through hole soldering so I figure with a small amount of advice I can make some meaningful improvements and learn along the way.

    Cheers - N

  8. #8
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    Yes, fill/flood/pour all unused areas on both sides. And connected all of these areas to each other with vias.

    How much difference this makes is unclear - a good subject to research.

  9. #9
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    To understand digital PCB groundplanes, this is a good tutorial: https://www.maximintegrated.com/en/d...ls/5/5450.html

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