$20 paypal to design me a PCB layout in CAD...details in thread

Discussion in 'The Projects Forum' started by chunkmartinez, May 13, 2013.

  1. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    As the title says....The TDA7293 is what I need a board for, but it will be stereo so for two ICs.

    The board Dims are:

    101mm x 152mm

    But not strictly so...

    In the following I will show a few different schematics which will comprise the different sections of the total circuit and let you know what spec component(s) used. I will give every detail needed...I also may have one or two questions on ideas.

    The pics are in the attatched below

    NOTES: I realize it is smart to have some protection circuitry, and also have different capacitors and rectifiers per unit(2 ICs, 1 opamp) but i'd like to start here and go with it and then maybe later redo a design when I learn how to use those CAD programs...

    Can I use two "simple switcher" circuits to reduce rails for the op amp? I figure a NEG rail is the same thing practically as a POS rail but in a different location in a dual supply right? current travels the same way as the pos rail but different phase so it should work?

    Btw, the SEC windings are +/-42V raw before rectification..Will rectification take me too high for the ICs? It says it can withstand +/-60V at idle.

    Also, in the main IC schematic, the shown 1mF power supply Caps are the ones shown in the main power supply schematic except the main schematic shows 6.8mF but I meant I am going with 8.2mF caps not 6.8...

    Thankyou for help...
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Why don't you just order the board from eBay. They went way ahead but you will likely only need to build half (not all four )

    Here

    All for $9 including shipping. If it is only a proof of concept for you. It is good to check because some of these all-in-ne audio amps are noisier (buzzer) than most people find acceptable. The eBay listing's recommended op amp NE5532 is a better option than tl072(my opinion for music).
     
  3. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    It would be much easier if you could put all bits of the schematic in one piece. Try using Eagle to draw the schematic. Maybe we can go from there.

    Matt
     
  4. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    I have seen them but they have their way of doing things...I am trying to learn in the process...Is the NE5532 really going to be better then a tl082? I have a BB OPA 2134 what do you think?

    If you guys will be so kind as to help me with any questions to do with eagle I think I might aswell just making this a learning thread for using eagle CAD...It's already installed on my comp.

    And I know there are Tutorials but they suck honestly...

    I need a little help with choosing the components in eagle since the names are not always obvious. What did you think of my idea on the simple switchers for the opamp guys?

    Also can you give me the names in eagle for the following:

    1/8 watt metal film resistors(precision tolorance if that matters)

    to-220 with 5 leads(simple switchers)

    My TDA ICs

    25v, 16v electrolytic aluminum caps

    ceramic disk caps

    the 4 legged silicon rectifier

    what do I do about pitch? Witch I don't know much about?
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The BB OPA 2134 will be best. Just use the 082 until you are done and tested. Then replace the 082 with the 2134. You will suddenly realize the snow storm in the background is gone.
     
  6. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Hi chunkmartinez.

    I agree--figuring out which components are the right ones can be quite difficult. That's why you search and get as close to what you want as possible. The only important thing, really, is the footprint. If the PCB footprint is the same, then you should be all set--just make sure it's labeled correctly on the board to match the component you're putting in. But since you aren't planning on designing the board yourself, all you have to worry about is make sure it's the right footprint.

    If this is a through-hole board, you shouldn't have to worry about pitch. It's usually 0.1".

    We'd need part numbers for the 5-lead to-220 switcher, just the information you gave will not be enough. Same with the 4-legged silicon rectifier.

    You should be able to find most of the other items fairly easily. Once again, just check that the footprint is correct (find the datasheet for the components on google, then check the sizes). That will help you choose the correct components in Eagle.

    Once you have the schematic put together, we can work on the PCB.

    Good luck!
    Matt
     
  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    In this grade of stereo devices, I think it would be impossible to hear any difference between a NE5532 and TL082 (both of which are excellent pre amp components). Based on context, I assume the signals in will be "line level" which is approxiamtely 0.5V @ 0dB. The noise from either the 5532 or TL082 will be inaudible (even through headphones). The most likely source of noise if you hear it will be hum from the transformer if it is not well shielded.
     
  8. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    You guys are awesome as usual....I will do some studdying and work in the SCH...and get back to you tomarraow..
     
  9. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    Oh, and can I get elaboration on exactly what footprint its?
     
  10. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    A "footprint" is the PCB design of a particular component.

    For example, this is the footprint of an LM555N timer:

    555.PNG

    If you look at the footprints for the 555 and, say, an LM393 op-amp (shown below), you'll notice they're exactly the same:

    393.PNG

    That's because both devices are in an 8-pin DIL package. Since the package is the same, the footprint will also be the same.

    Hope this helps!
    Matt
     
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  11. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    okay so I just look for the same package....reguardless of component.
     
  12. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Well try to find the right component. Just keep in mind that if you use just any device with the same package, that device has to be put in your schematic, which you want to avoid. But, for example, let's say you're putting in a 1N4004 diode, and the only one you can find in Eagle is the 1N4007. The devices operate similarly and have the same footprint, so you can often just replace the 4004 with the 4007.

    Oh, that reminds me--eagle search requires all parts of the component name. So if you're looking for a 555 timer, you can't just put in 555. You have to type in LM555N or something like that. Same with the diodes--you'll have to type in 1N4007 instead of 4007, and so on.

    Just remember that when your board is finished, you want your schematic to still be right, so don't go swapping out every component just to match footprints. The board and the schematic are linked--changes on one affect the other.

    If you have any questions, feel free to ask, I've been using Eagle for several years and have really grown to like it. I've designed quite a few boards with it and would be happy to help in any way I can.

    Regards,
    Matt
     
  13. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    You can actually search for example for *555* which will find anything that has 555 in it.
     
  14. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    No, Eagle doesn't do that, at least not the version I have (6.4). Some other programs, i.e. Proteus, maybe KiCAD do, but eagle does not.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    Well, you really should use a component with a pinout that matches the actual item you'll be using; as otherwise the Erc (error check) reporting will likely not be accurate for that part.

    It's important to use Erc early, and use it often - otherwise your life will be unpleasant until you make the Erc report happy.

    Cadsoft's Eagle is a good product, however the demo version only allows a 2-layer board up to ~3" x ~4" in size, and you're talking ~4" x ~6" - so, unless you're plan ning on registering Eagle (which is not inexpensive), you'll have a bit of a rough time.

    You might consider using surface mount components, as your design may wind up considerably smaller than with thru-hole components.
     
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  16. SgtWookie

    Expert

    Jul 17, 2007
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    Interesting that they would have removed such a useful feature. I've been using Eagle since v4.12; and even that version allowed searching the libraries with wildcards.

    [eta]
    V6.1 does have the search w/wildcard feature, available when you attempt to add a component to a schematic, at the bottom of the dialog box.
     
    Last edited: May 17, 2013
  17. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I am pretty sure it does.
     
  18. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Thank you Sgt, I should have mentioned that the device has to have the same pinout. Thanks for posting that.

    That is also a good point about board size. Personally, I think you'll be able to fit everything on the board allowed by the lite version, but if you can't, surface mount is the way to go. It's more difficult to assemble, but may be worth saving what it would cost to upgrade Eagle :p
     
  19. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Ha! Whaddaya know? :D

    I guess I didn't realize you could use asterisks like that, I was trying to just type in 555.

    Well this is embarrassing.... :rolleyes:
     
  20. SgtWookie

    Expert

    Jul 17, 2007
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    You learned something new; that's not embarrassing, it's what the forum is all about. ;)
     
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