electronic design request

Discussion in 'The Projects Forum' started by cyber5, Jul 18, 2013.

  1. cyber5

    Thread Starter New Member

    Jul 18, 2013
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    hello folks,
    i am new to this forum,
    came here for one purpose, i was directed here by someone who said that the most knowledgable are here
    i know nothing much about circuits and components,

    i have a small circuit board that functions as an adjustable voltage step up regulator,
    it measures about 3-4 inches sq in total,
    it contains 23 components in total, of which one is a coil, a rheostat, 2 are capacitors, 2 seem to be 3 legged mosfets, a 8 pin IC, and the others are fine components; maybe diodes or resistors,
    it is on a printed circuit board that i believe is a 2 layer

    i want this circuitry to be redesigned to a different layout with a few upgrades using whatever computer program is needed.
    I have a company willing to produce the new PCB for me but they need the schematic done and sent to them,

    Is there anyone on this forum who is qualified, able and willing to do this job,
    i will send you the circuit
    I am willing to pay accordingly for the service

    Please email me at <snip>.
     
    Last edited by a moderator: Jul 19, 2013
  2. wayneh

    Expert

    Sep 9, 2010
    12,103
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    No offense but that is something that is widely made in China and can be obtained very cheaply. Is there something special you want to do?
     
  3. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
    0
    yes want it custom made to my specifications,
    very high power handling
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    What do you consider "very high power handling"? Can't be too high power if it is only about size of the palm of your hand.

    You need to give much better preliminary specs in order for anyone to decide whether they might be a suitable match for your needs.

    What kind of input?

    What kind of output? Voltage, current, range of adjustability, max ripple.

    What features are you looking for?
     
  5. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
    0
    i have the circuit already which does just over 200 watts,
    just need someone to break it down and redesign it to a different shape, possibly upgrade the power handling a bit

    i will send the functional circuit to whoever is willing
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    What are your specifications?

    The usual way of finding someone to design a custom circuit like this is to put together a set of specifications and then put them out for bid.
     
  7. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
    0
    power rating like 300 watts, if more even better like 500 watts
    input voltage 8-15v,
    output 14-19v (always higher than input voltage)

    made for external heatsink use

    must be able to run to max power output - no protection turn off

    anyone?
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    We do not encourage off line help. Please post schematics on this site so everyone may learn. Kinda goes with my signature.
     
  9. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,036
    Hmmm.... 30A boost converter in a 3x4" footprint plus heatsink. Tough but not immediately impossible. You need a whopping inductor.
     
  10. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
    0
    can you handle it?
     
  11. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
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    ok, i dont have schematics though, thats what i want done!
     
  12. Papabravo

    Expert

    Feb 24, 2006
    10,138
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    To help everybody out I offer a few back of the envelope calculations for your consideration.
    Code ( (Unknown Language)):
    1.  
    2. Boost Converter
    3. Power Out = 300 Watts
    4. Assumed Efficiency ≈ 80%
    5. Implied Power In = 300 / 0.8 = 375 Watts
    6. The worst case is when the input voltage is 8 Volts
    7. The input current will be 375 / 8 ≈ 46.9 Amps
    8. The inductor will need to handle two times this current or ≈ 94 Amps
    9. None of the cores I usually use for SMPS applications will handle
    10. this much current.  I will continue my search.
    11.  
    These current levels exceed what I would consider reasonable for printed circuit boards with 3 oz. copper and the connectors alone would chew up the available real estate. IMHO I don't think it can be done with those specifications at that size.

    In addition I think 500 watts is a complete impossibility with that size restriction.

    Consult this datasheet for typical design formulas
    http://www.onsemi.com/pub_link/Collateral/MC34063A-D.PDF
    Of course you have to use an external switch.
     
    Last edited: Jul 20, 2013
  13. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
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    I could do it as an isolated stacker converter. It only needs to generate an average 16.5v from an average 11.5v, so with stacking that requires only 4 volts at 18A to be added on top of the original input voltage of 11.5v.

    So it requires an isolated SMPS 4v 18A supply, which is only a 72 Watt SMPS, easy enough in that form factor.

    I have too much commercial work to take on this project, and I have a feeling you don't really want to pay commercial pro rates for design anyway. If so, your question would read more like; "Can someone design and refine this for production for 6-10 grand?"
     
  14. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
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    thanks guys for putting thought into it,
    i never said there was a size restriction though,
    the only restriction is that i need all the fets or whatever those 3 legged things are that bolt on to the heatsink to be on one side so it can bolt on easily
     
  15. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Reread your first post.:p
     
  16. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
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    i was describing the circuit i had currently that i wanted to upgrade!

    i know it must be a bigger size, maybe if i can get it on a 4x4 board will be great
     
  17. WBahn

    Moderator

    Mar 31, 2012
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    This is hardest part of dealing with most customers -- getting them to tell you what they need. In fairness, if they knew what they needed, then there would be a decent chance that they wouldn't need us.

    But keep in mind that we are not mind readers. Given a lack of anything resemlbing actual specs, we have no choice put to read between the lines and infer things from context. If you are telling us about a circuit that is a certain size that you want redesigned to a different layout, we have to assume that you are telling us the certain size because you want the new layout to be comparable. You tell us you want new features but, unless I missed a post, haven't given any hint as to what those features are. In fact, you haven't told us what the features are of the present one that you want to keep. You now say that you know that it must be a bigger size, but how are we supposed to know that you realize that or that it is acceptable. Again... not mindreaders.

    You need to spell out what is important to YOU for this power supply. Think of it from a functional perspective. You have reasons why a COTS (commercial off the shelf) supply won't work for you. Why not? Unless you tell us why those are unacceptable, how do you know that the custom one that someone designs for you won't be unacceptable for the same reasons?

    So ask yourself questions like: If the thing weighed 10lb, would it be acceptable? If yes, then ask if it would be acceptable if it weighed 20lb. If no, then ask if it would be acceptable if it weighed 5lb. Keep going like that until you settle on a weight for which your best estimate is that if it weighs less than that it will be acceptable and if it weighs more than that it won't be. Then do the same for physical dimensions. Then think about temperature the same way: Do I need the thing to be able to work if the ambient temperature is 100°F? Do I need it to work if the ambient temperature is -40°F. Keep moving those limits until you find a range that you feel comfortable making the specification.

    You appear to want it to be adjustable. How do you want it to be adjusted? With a 1-turn pot that someone grabs by hand? With a 10-turn trimpot that someone uses a pot adjustment tool for? If you want the output to be set, say, to 1725V, would 17.26V be acceptable? Would 17.5V? Again, move the limits around and ask yourself what is acceptable for YOUR needs. We can't do that for you.

    You say the output voltage is always greater than the input voltage. By how much, as a minimum? If the lowest voltage you can get out is 1V higher than the input voltage, is that acceptable? 1.5V? 0.5V?

    Does it have to be able to deliver 300W regardless of the output voltage that is chosen?

    How is this thing going to be cooled? Just a heatsink sticking out into the still air? With a fan blowing over the heatsink?

    What kind of connectors do you want on it? Other than a voltage adjustment, what other controls do you want? Power On/Off?

    There are also going to be questions that you won't know to ask or how to answer them even if you do. Topics that might fall into this category would include how much ripple voltage is acceptable? Those are things that need to be discussed, usually by you giving enough information about what this thing is being used for so that we can figure out what questions to ask you that will help us either figure out what the limits should be or to educate you enough about what the considerations are so that you can figure them out.

    At this stage, none of these specs are set in stone. But the more time and effort you put into them up front the smoother things will go, the cheaper it will be, and the happier you will be.
     
    absf, THE_RB and blueroomelectronics like this.
  18. cyber5

    Thread Starter New Member

    Jul 18, 2013
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    I completely understand your point and appreciate the time you put into this thread.

    Let me explain better. I want a device made with my name on it. Its for use in a new product we are planning forna small industry. I cannot disclose too many specifics on a public forum. I wish my pm was working. Idk why it is not.

    With regards to some of the need to knows you raised below, I have not a problem answering those. Remember im totally half dumb when it comes to electronic circuits compared to you guys.

    I outlined the size requirements, did not know weight would be an issue, but as light as possible shall suffice for that, it will be using a high powered fan cooled heatsink. Yes the voltage should not fluctuate from the set point set by a small potentiometer or with 2 terminals placed so I could solder in different resistors for different voltages, no fluctuations within the rated power range, after overloading voltage fluctuations would be expected, the device must be able to run to maximum power withoUt any protection circuitry. It needs to have a remote signal turn on circuitry so that power in power out and ground can be connected at all times but the device can be off. I would assume it would need to have at least 8 awg power connectors, maybe a small led to show it is on, it should be able to be run in parralel with another same unit both set at the same volts out for applications that require increased power handling.

    What else needs to be known? I will tell if I could.

    The main thing is that it is a product with whatever name I want to put on it, that ppl will not be able to outsource.
     
  19. cyber5

    Thread Starter New Member

    Jul 18, 2013
    11
    0
    More responses to your questions, heat should not turn it off, my heatsink will be adequate. It should be able to work in any climate from 0 to 40 celsius. The minimum voltage above the input voltage I would like to be 0.5volts. For eg if it has a no load voltage in of 12.8v it should give 13.3 at the lowest pot setting.

    Wrt to the power rating, Im referring to the power out to be 300-500watts the higher the better. 500watts would be perfect. The current device i use sees a current in of 26a maximum anr has only been run off a 12-14 volts in. Thats 300watts plus in right there. The power out I know will change with difference in efficiency at different voltages out. ive measured 20a maximum out at 15.7v out already.
     
  20. WBahn

    Moderator

    Mar 31, 2012
    17,737
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    Things like "as light as possible" and "should not deviate" are useless when it comes to making specs.

    If someone designs something that weighs 15oz and it could have been reduced to 12oz (or even 14.9996oz), then the design provided was not "as light as possible" and is, therefore, unacceptable.

    If the voltage is set to 14.3V and a minute later it is 14.300000001V, it has deviated from what it was set at and, according to your description, this is unacceptable.

    The first one you can sidestep pretty easily by saying something like, "Weight is not an issue, but should not exceed 15oz, if possible, and should be reduced where practicable."

    This gives the designer a target to shoot for. If their design comes out to be 24oz, they know they should probably devote some effort to reducing it. If it comes out to 13oz, they know that they should focus on other things first and only do consider simple and obvious things to reduce the weight, and if it comes out to 17oz, they should again consider mostly simple things, but it should be a bit higher on their priority list.

    The voltage deviation spec is much more important. If what this thing is powering can tolerate a deviation of 10% either way, then making a supply that holds the voltage to 1% will be unnecessarily expensive and possibly not commercially viable. But if it is the other way around, the supply may be nice and cheap but will not perform adequately and get a bad reputation.

    We you say "remote", what are you talking about? A wired switch? A wireless connection? WiFi? Internet? Infrared?
     
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