Basic concepts PCB building PIC/dsPIC

Discussion in 'The Projects Forum' started by Electron_23, May 6, 2014.

  1. Electron_23

    Thread Starter New Member

    May 6, 2014

    I am studying electronics engineering and this year I have been asked to develop a Micromouse/maze solver. For that I will use a dsPIC33E controller, two voltage regulators to 5V and 3V3, a dual motor driver, two magnetic encoders, and some sensors. My question is pretty simple, because my problem is that I have never built a PCB so I do not really know the process. The questions are:
    - Do I have to design it in Eagle, make the PCB manufactured without the components, and solder they by myself? Or when you order it to the manufacturer you also give them the components and they solder it?
    - For the dsPIC33, what do I have to connect in the schematic apart from the components I mentioned above? I mean, I guess there has to be some pins for programming or communication with the computer when programming, right?

    Sorry for these basic questions but I am not familiar at all with this kind of things.

    Thank you very much in advance.

  2. wayneh


    Sep 9, 2010
    I would skip the PCB step unless it is required. You can make your own build on a perfboard. You'll do your own soldering, but this is a small price to pay for the time you save not making the PCB. Any problems - and there will be problems - will be much easier to fix.
    Electron_23 likes this.
  3. Electron_23

    Thread Starter New Member

    May 6, 2014
    Thank you for your answer. I will have to build the PCB after all, so I will have to deal with it. Do you know if the manufacturer gives you the components soldered, or how does that work?

    Thank you again.
  4. sirch2

    Well-Known Member

    Jan 21, 2013
    Eagle is quite a good product for free, I'm sure others will be along with their own recommendations. You can make your own boards - google "PCB etching" and "Toner Transfer". If you want a company to make the boards then Iteadstudio - are about as cheap as you will find. The thing about using a commercial board house if you have no experience is that you may go through several iterations of your board and so it can get expensive and the lead time can be a couple of weeks.

    In terms of Eagle, you would need an Eagle library part. You may be able to get this from the Microchip website or DesignSpark, failing that you can draw your own in Eagle, it's not that hard especially if you find a component with the same package type and then copy it and rename the pins.
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    You can either buy bare boards from someone like itead as suggested above.. Or you can get the boards delivered to you with all the components soldered already.. (don't think itead does that but there are MANY others)

    Obviously for low volume its going to be very pricey to get a few or single board fully populated with components.. Because the fab house has setup time/min component buys,etc... Expect a few hundred dollars minimum..

    As for the software.. Many use Eagle.. I use Diptrace as I hate eagle and find it much more difficult to use/learn compared to Diptrace.

    Or you might start with something prebuilt and just write the code for it.. Can't get much easier than this for a project like yours
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Have you recently visited China to check out their board manufacturer and assembly houses?

    OK, me neither, but I do have a link to some on EBay. Most any house here there or anywhere can take the Gerber file output of any PCB design program and turn it into real boards for you.

    From several China suppliers you can literally get a 4x4" PCB, single quantity, into your hands for under 10 bucks. Takes 2-3 weeks for the mail to work, but the price is unbeatable, and you can of course pay more for quicker shipping. Of course for a little more you get more boards. Spares are always helpful!

    My preferred PCB design program is Kicad. I have used it for both personal and professional work. Completely free, open source (not that I've ever even looked) and very complete package allowing you to lay out the schematic then place the part pads and wire them up. There is even a freebie web based auto router that works with it for the simple traces (do the power routings yourself first, then let it play).

    Design packages such as this try to eliminate many common mistakes. When schematic and layout are linked together they do not allow you to connect points that should not connect. They all come with “Design Rules Check” (DRC) routines to check for minimum separations and the like.

    As far as assembly goes, expect to pay on the order of $1 USD per component to have them placed for you, and that’s on top of your cost just to buy the parts. For that much money I’d ask around for anyone who has assembly equipment, some sort of reflow oven, or someone with a steady hand who will work for pizza and beer*.

    When pushed for time once I even reflowed a SMD board on my stove top. You can buy a syringe of solder paste and squirt it on the pads thru a small tip. This *will* leave a small mark on the plunging finger. I have a little plastic gun that holds the tube for a no-hassle application.

    With that said, don't build a PCB right away. Make a breadboard first. I breadboard using SMD parts for many reasons, mostly that is what the final board will use and I find it easier to use then thick leads.

    At least with a breadboard you have worked out all the electrical kinks before commiting to a PCB.

    Even doing it this way, don't expect board #1 to work 100%. Hopefully a few cuts & jumpers will fix, but do not be upset if you need to respin: the industry average is 2 to 3 boards to get everything "close enough" to 100% acceptability.

    * Remember: only supply the beer AFTER the board is soldered.
  7. Wendy


    Mar 24, 2008
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    For a prototype surface mount I had to do I simply ordered the boards from itead and soldered all the components by hand with a $80 cheap-o hot air gun and some solder paste in a syringe.
    Pain in the A&$ but FAR cheaper than having the delivered fully populated..
    Took me about 1 hour per board to solder and each board had 30-40 components from op amps to resistors/caps,etc..

    0402 resistors,etc.. are a pain in the butt.. Just use a microscopic dot of solder paste and it should be fine.. any more than a microscopic dot and those suckers will walk all over the place/tombstone,etc..

    multi-lead IC's are simple to solder.. just drag a line of paste..stick them down and hit it with the hot air.. The solder will flow exactly where it needs to go.
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    What a lot of people do is buy a small module with the PIC already on it, and header pins. That will have a programming connector too.

    Then buy a small dual DC motor driver module. Then the "build" becomes as simple as plugging header wires between the two modules and attaching the PSU and sensors (which also plug in).