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How to design a circuit

  1. Dec 8, 2011 #1
    So you made your circuit on prototype board, and everything is ready to good it works etc.

    How do I design it so it looks tidy and neat?

    Are there any rules, hints, tips to make circuit look neat and clean and all that good stuff?(Talking about finalizing for PCB board)
     
  2. jcsd
  3. Dec 8, 2011 #2
    Practice, practice, practice! :biggrin: Seriously, when I began experimenting with electronics in the 1970s, we just hand sketched layouts on paper until we were satisfied. I don't know what the professionals were using.

    Lately, a commonly used tool for hobbyists is the free version of Eagle PCB. It has an "auto-router" that helps put things in the right places.

    There are tutorials and user forums scattered around the 'net, too. Just search "eagle pcb".
     
  4. Dec 8, 2011 #3
    Thanks for the link I will definitely check it out. I did overhear my teachers talking about that program before but never took it seriously.(as I didn't even know how a transistor works).
     
  5. Dec 8, 2011 #4
    A free pcb layout software? What is the limitation on it? How big the board, how many layers? Can it support OrCad schematics?
     
  6. Dec 8, 2011 #5
    I think it will support needs of my humble knowledge of designing such circuits, which is basically nothing.

    I already downloaded it. It looks ok. And free is totally in my budget :rofl:
     
  7. Dec 8, 2011 #6

    berkeman

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    Staff: Mentor

    The free version does have limitations (I don't remember them offhand). I think they also have an inexpensive version around $100? that does much more. You end up ordering the PCbs through them, I believe, which is why they offer the free intro version.

    EDIT -- Oh, and it's schematic and PCB layout combo software, I believe.
     
  8. Dec 8, 2011 #7
    One good method that is especially suitable for prototyping boards and RF work is to design the separations, not the connections.

    Instead of designing tracks to connect components' pins or pads you draw lines on the circuit, isolating the nodes and knife cut or rout these into the blank PCB.
    This divides the pcb into a series of copper lands and minimises the copper removal.
    Because these lands tend to be chunky they have low capacitance inductance, relative to tracks and this makes the technique good for RF work.

    A final advantage is that slight misalignment of drilled holes is less serious and easier to cope with.

    The main disadvantage is that it does not result in pcbs suitable for production work.

    go well
     
  9. Dec 8, 2011 #8
    So they get you when you order the pcb from them? How much more compare with if you just sent in a Gerber file from OrCad?

    Is the software as good as OrCad PCB? I know the older 9.2 version that I really like. I like it better than Power PCB for RF layout because it gave me the freedom of customize the copper pour etc.
     
  10. Dec 8, 2011 #9

    berkeman

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    Staff: Mentor

    They are kind of a low-end fab house (maybe even offshore with some shipping delay in the fab cycle, but I'm not sure). Their software is not anywhere as capable as OrCAD PCB, I believe.

    We had a thread in the EE forum a while back describing the different low-cost / simple PCB fab options and fab houses. I'll see if I can find it with a search...
     
  11. Dec 8, 2011 #10

    berkeman

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    Staff: Mentor

  12. Dec 9, 2011 #11

    In the meantime I fried my whole working circuit. ( misplaced + and - terminals).

    But I learnt a valuable lesson.

    PROTECT EVERYTHING WITH DIODES!!!!

    10 hours of good work. publack... just like that.
    Its somewhat good that i fried it, its better for me to fry it than my customer, am I right? :D


    But about that design, should I make a point at PCB, which I will declare as ground? Will that simplify things?

    Same for the Vcc point... or +.
     
  13. Dec 9, 2011 #12
    If you make a PCB with more than 15 components or so or very fine pitch ICs, I highly recommend investing in a solder mask layer. I learned this the hard way when my flux contaminates kept shorting out components and cost me more in spare parts and time than the original solder mask option did.
     
  14. Dec 9, 2011 #13
    You need to be a little bit more specific on what you are doing. A lot of decision are made base on a particular situation.
     
  15. Dec 9, 2011 #14
    http://pokit.org/get/e212cc400b6d6f4eddcc49bc17d7e2cd.jpg [Broken]

    This is my circuit. I am trying to pack this as neat as possible.
     
    Last edited by a moderator: May 5, 2017
  16. Dec 9, 2011 #15
    If that is all the circuit, all you need is a two layer board. With this, is not even essential using a ground plane.

    You should have a 0.1uF ceramic cap right across the Vcc and GND of the 555. Yes, you have 24V and you should use a Schottky diode from power input to the circuit board so if anyone reverse the battery, you won't burn anything. Although you do have 1.5K resistor acts as current limit that limit to less than 25mA or so. That really should not burn up the whole thing. Make sure C1 and C3 close to the IC. With this small circuit, I would not use surface mount. Use a 1/2W resistor for R1 because it is of high value. If you have any solder flux from not cleaning good, it will cover the body of the resistor and start conducting a little and lower the apparent value of the resistor and cause inconsistent between different boards. A long body of a 1/2 W mitigate this problem. Using surface mount in high impedance circuit will risk dirt trapped between the resistor and the pcb and become a conductance of some sort.
     
  17. Dec 9, 2011 #16
    Well this is more complicated than I thought. Good thing I won't be doing it then, my teaching assistant will, I will just try to design it.

    I just made a mini-dynamite voltage regulator. I will use them, instead of that voltage divider you see.

    I intentionally wanted to see what happens when you connect input to output pins. hahahaha it was fun. The whole thing exploded (the regulator) :D

    I have a bunch of them lying around... :P

    Dont worry I was 2m away :)
     
    Last edited: Dec 9, 2011
  18. Dec 10, 2011 #17

    MATLABdude

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    Science Advisor

    PCBs are expensive, unless you're going into bulk production of something. I tend to make fairly simple circuits (which are, more importantly, usually one-offs) so I usually end up building my (non-breadboard) circuits on perfboard (the fancier stuff with the metallized tracks). Stuff that looks like this:
    http://www.circuittest.com/prototyping/solderable-breadboards

    You can easily cut them to size, solder wires and components to them, and break connections using an x-acto (or even more easily, a small drill bit). But yeah, even there, neatness and proper routing go a long way towards making something that works (or fixing those that don't initially).
     
  19. Dec 10, 2011 #18
    Expensive? I got medium sized one, ready for printing for like 3 euros. 11x15cm (something like that)
     
  20. Dec 10, 2011 #19
    You from Europe? How do you get cheap pcb done. I am doing some small pcb and will cost me like $600 to get a minimum run here!!!
     
  21. Dec 10, 2011 #20
    I meant PCB blank board. I will do putting components and soldering etc. myself with my teaching assistant.
     
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