Request assistance with pcb layout

Discussion in 'The Projects Forum' started by timjea, Jan 14, 2011.

  1. timjea

    Thread Starter New Member

    Jan 10, 2011
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    I'm asking for some skilled help in developing a compact pcb design. I'm a first time Eagle user (version 5.11). I've invested three hours and I have the schematic entered, and have no idea how to efficiently lay out the parts. The goal is to to establish the pcb, then somehow duplicate it to make 4 at a time (reduced production cost?) and submit to BatchPCB.

    The circuit - I merged two almost identical circuits to make one PCB and then will only install the components appropriately to which version I need. Either Q1 and its associated terminal block is installed OR Q2, R9 and its terminal block is installed. Installing Q1 and the circuit is adjusted by R2 pot to turn ON a load as the temperature rises above the set point.(ie turn on a computer fan). Installing R9 and Q2 and the circuit is also adjusted by R2 to turn OFF a device as the temperature rises above the set point.
    Rh is to set the hysteris (seperation) of the on/off. Omitting that resistor on the test circuit yeilded about a 1-2 degree difference. I would like about a 3-4 degree difference to avoid cycling but do not know how to calculate the value of the resistor to acheive that. That is not very important right now as I can work on figuring that out later, maybe even trial and error.

    If it matters the temp sensor is a 2N2222 or 2N3904 with the base and collector connected to terminal B and the emitter connected to terminal A. The current temp range is from 0 to 300deg per the original circuit. I will be using the circuit in the 80 to 100 degree set point range.

    Currently I think I have selected the wrong schematic part for the 7805 voltage regulator, and also the wrong part for the darlington pairs Q1 and Q2 as they all seem to be for horizontal mounting and not vertical mounting. I do not find a vertical mount component option. I would appreciate some help on that too.

    I have few preconceptions for what should go where on the board other than it seems to make sense if Q1 was near its terminal block, and Q2 be near its terminal block. Remember Q1 and Q2 are installed exclusively - one or the other not both.

    Lastly, it seems that the traces supporting current flow through the darlington pairs may need to be bigger than the others to support the higher current flow. I'm trying for overkill here by planning for 1A. I can't figure out how to control the trace width.

    I've been attempting autotrace, and I've gotten real good at Rip Up. I am attempting to upload the .brd and the .sch eagle files. Hopefully I have followed all of the rules for this forum.

    Your assistance would be greatly appreciated. I'm not trying to mooch off of anyone, but I am frustrated and tired. I've put in a lot of effort and not much to show for it.

    Thanks in advance-
    Dane
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    I'll see what I can do for ya Doc.

    Give me till Monday!

    Edit: I've got lots of library additions in mine. I'll see if I have the right components, if not, I'll use ones with identical footprints to the ones you want.
     
  3. timjea

    Thread Starter New Member

    Jan 10, 2011
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    I went to the BatchPCB website and see in their FAQ that there is no cost difference or savings to put multiple circuits in the same layout becasue they simply charge by the square inch. So we don't need to do that. They also highly recommend that we put a frame around the whole circuit either on the copper side or the silkscreen side so they will know where to cut the board. I will be order 10 at a time. I see that their minimum trace width is 8 mil on the copper side.
    --------------------------------------------------------------------------------
    Can I put multiple designs in the same board/layout?
    Yes you can - but we don't recommend this. The fab house will not separate the boards - you will need to cut them apart yourself. If this is what you want that's fine - but you have been warned. In the past people did this to get a better deal as each design was rounded up to the next inch - we are no longer rounding up (except for the first inch) so this won't save you anything now.
    How do I indicate the shape of my board?
    This is normally done with an outline layer, or a silkscreen layer. You can use any method you want but please use one! Something as simple as a rectangle on the top overlay (aka. silk) layer is great! Note: you can also make the outline in a copper layer (this is a trick mentioned in the SparkFun tutorial - but be sure the outline is at least 8mils thick! Otherwise the design will fail since the DRC doesn't know that this is not a trace.
    Multiple humans will be looking at your design and will let you know if we are unable to figure out the board shape. This may place your design on hold and cause added delays or it may result in you receiving a board that is not cut as you expected! So, an outline is strongly recommended.


    --------------------------------------------------------------------------------


    I didn't think to put some mounting holes on the corners of the board. 2 in the middle or 4 on the corners, doesn't matter as it will be on plastic standoffs and screwed to wood. IS there a specific item for a mount hole or do I just choose a terminal hole and connect no traces to it?
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Eagle provides a Drill layer, as well as Restricted zones, which stop its auto router from using the zone for traces.
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Here ya go. It's DRC checked and error free.
     
    • 2.brd
      File size:
      14 KB
      Views:
      15
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    That looks really good. It's nice to see someone who also uses fat traces, unless narrow ones are really needed. John
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Thanks

    I've got another version I didn't upload. It is the 'minimum copper removal' method, with blocks of copper and small seperations. Also called a milling outline method.

    Let me know if you want to see it instead.
     
  8. marshallf3

    Well-Known Member

    Jul 26, 2010
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  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    The OP may want to see that. I don't do milling, but I also do something similar in my final designs. I see no disadvantage in minimal removal for ordinary stuff. I think they look neat, it saves etchant, and it reduces the amount of copper salts for disposal. Albeit, it is not very much in terms of milligrams, but it is eco-friendly and painless. I've also noticed that many of the evaluation boards are designed that way. John
     
  10. timjea

    Thread Starter New Member

    Jan 10, 2011
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    Thank you - that looks great. I played with it off and on during the weekend but never could get it all the traces on the bottom without atleast one or two jumpers. I see how you tweaked the component positions and how you necked down the trace between the ic legs. Thats a neat trick.

    Thanks for pointing me to the LM35, LM335 or LM94022. I'll check them out.

    I'll post again after I get a little further along.

    Dane
     
  11. nerdegutta

    Moderator

    Dec 15, 2009
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    Had some time to kill.

    Topside:
    [​IMG]

    Bottom side:
    [​IMG]

    Not sure if I selected the right component for the screw-connection-thingys... ;)
     
  12. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Hey, I like it. What program did you use to render that pic?

    So anyway, I took the milling outline and blacked it out for using in a toner transfer method. Or use it in photo reverse and mill away all the black lines.
     
  13. capnray

    Member

    Jul 3, 2010
    59
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    I use express pcb, based on intellicad, nice schematic capture and PCB layout. I retired after years of using high end stuff, Express has it all and if you can stuff everything on the small board, you get three for a base cost. I learned in the early '80's that an "included library" was not a perk, needed to modify them.
     
  14. nerdegutta

    Moderator

    Dec 15, 2009
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    Yes, its quite nice.

    I used Eagle3d to make a *.pov file, and that file was rendered in PovRay.
     
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