Building a custom PCB

Discussion in 'The Projects Forum' started by james211, Sep 11, 2013.

  1. james211

    Thread Starter Member

    May 29, 2012
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    So I came across this cool site, http://123d.circuits.io/ where you can build your own circuit schematics, and it gives you the option to order a PCB from your design. The problem is I have no knowledge of how to do this. I downloaded eagle and took a look at that and it confused me even more.

    I have been able to design exactly what I need through a series of pieces and a breadboard, and I'd love to be able to build it as one complete PCB rather than outsourcing the PWM and the buck converter.

    See the attached picture to see what I currently have.

    Here are links to the buck converter and the PWM controller.

    With all the info given, what do you think it would take to have one PCB eagle file built and a parts list so I could just order the parts and put the board together myself?
     
  2. nerdegutta

    Moderator

    Dec 15, 2009
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    If you can draw it on a piece of paper, I'll help you with the Eagle files. After that, we'll see how to do the PCB layout...:)
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    If you want a simpler process you might try an integrated schematic and layout design software, and fab service such as 4PCB or Express PCB. Their software is generally easier to use for simple projects. Their board costs may be somewhat higher than some of the other large fab houses but the cost difference is not that significant for small quantities.
     
  4. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    OK, so here is what I have so far. I have the schematic from the PWM controller, I have a schematic for voltage reduction from 12V to 5V. Since I have little knowledge on this end, I would need help combining the two schematics, as well as adding in the power supply and LM7812 Voltage Regulator. Does that make sense? I've attached the two schematics as well as a super dumbed down sketch of how this would work on the PCB.

    If there would be a fee to get a finished eagle file made for me, please let me know what this would cost and we can discuss over email or PM.

    Thank you!!
     
  5. nerdegutta

    Moderator

    Dec 15, 2009
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    Let's first find out the goal.

    What do you want to do?

    Do you want one 12v fan running at a constant speed?
    A 3.3v fan run from the PWM controller?

    The ATtiny is a micro controller. Do you have the software?
     
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    One thing that is only done in the very rare exception is to commit to a PCB without first seeing a working prototype.

    Make sure ALL your ideas work before you go thru an expensive process (unless you found the same EBay guy I did that sells 5 custom boards (2x2") for 20 bucks).
     
  7. Wendy

    Moderator

    Mar 24, 2008
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  8. nerdegutta

    Moderator

    Dec 15, 2009
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    Hi.

    This is a start.
     
  9. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    12v fan running at constant speed and the air pump motor will be controlled by the PWM controller. As for the ATtiny, I do have the code, I just need to find or build a programmer for it.

    I looked at your process nerdegutta, looks cool! Not sure it's my thing though considering I live in an apt in NYC. I appreciate your help.

    I saw your first schematic, but haven't looked close at it yet. With regards to a working proto PCB prior to having it printed, what is the best way to ensure it works? I know it works on a breadboard but a PCB is definitely different no?
     
  10. nerdegutta

    Moderator

    Dec 15, 2009
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    I draw my schemas from breadboards. Carefully checking every wire and connection.

    When I think it's OK, I make a PCB. When the PCB is done, I check for shorts with my DMM. The solder process starts with the power input, and the regulators.

    I must admit that I have a small pile of useless PCBs:(
     
  11. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Hey Nerdegutta,

    So I was almost able to complete a replica of your schematic. I couldn't find the symbols you used for the power supply or fan though.

    I'll rebuild the schematic from the PWM as well so I have it. Hopefully you can help me incorporate all these together properly then?

    Thank you!
     
  12. nerdegutta

    Moderator

    Dec 15, 2009
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    I've done some editing. Far from done, but here goes.

    The circuit is in two different sheets. One with the power block and the other with the ATtiny13A. There is something in that circuit I don't quite understand, and that is the parts connected to U1 pin 5. I assumed that the parts from J2 and to the right is a voltage regulator, so that's in our sheet 1.

    The diodes (D3 and D1) and Q3, are not the same as in the original circuit, but I used components I hope have the same symbol and footprint.

    Attached you'll also find the part lists. When the schematic is OK, we'll move on to the PCB design.
     
  13. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    You did a lot! Damn man...

    I spoke with the guy who made the original PWM controller and he's going to send me the eagle file today or tomorrow. I'll send it to you as well and maybe that will help you out. I had some troubles finding his components as well.
     
  14. Experimentonomen

    Member

    Feb 16, 2011
    331
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    Thats NOT a logic level fet, so you need ATLEAST 10V on the gate for it to turn fully on.

    If you drive it with only 5v on the gate, it will only be about half turned on = alot of heat will be generated.
     
  15. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    I spoke with the original developer, he claim's he's tested it down to 3V just fine for extended periods of time.

    Also, I have the original eagle files now, so hopefully with help I'll get this figured out!
     
    Last edited: Sep 17, 2013
  16. Experimentonomen

    Member

    Feb 16, 2011
    331
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    thats bs!! at 3v, the fet has barely even started to open.
     
  17. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    Nerdegutta,

    Why do the schematics need to be done on separate sheets in eagle?

    Also, I have some specific dimensions for the PCB, is there a measurement feature in the eagle board layout? I would have to assume so...

    Any suggestions on US PCB developers that have quick turnaround?
     
  18. nerdegutta

    Moderator

    Dec 15, 2009
    2,519
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    They don't. I do it sometimes to save space.

    On the vertical menubar there is a measuring tool.

    No, I do not know any developers.
     
  19. pwdixon

    Member

    Oct 11, 2012
    488
    56
    Are you trying to recreate a previous design and do you have the rights to do this?

    From the original schematics you appear to have swapped the drive FET, the new FET has a much higher Rdson which is probably going to make it warm up, perhaps even too much. The new FET also has a higher Vgs(th) which might cause a problem in turn on.

    You said I think that you have the code but is it source or hex? ie. can you change it?

    I would say the regulators are likely to get warm too, there are better more modern ways to do the same thing.

    When you ask about pcb developers do you actually mean a circuit designer, a layout designer or do you mean pcb manufacturers (blank or populated)?

    In terms of the pcb outline, if you have a specific outline drawing you should be able to import it into eagle pretty much directly.

    I do this kind of stuff all the time, designing circuits/pcbs and setting them to work, something as simple as this should only take a few days to design and a week or two to get the blank pcb and prove operations.

    Is this a commercial job or just a hobby? I'm not in the US (I'm a Brit) but I do do this kind of work for people, if that's a route you'd like to pursue PM me.
     
  20. skeptor

    New Member

    Feb 5, 2013
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