Looking to pay someone to assemble a circuit

Discussion in 'The Projects Forum' started by aves911, Mar 28, 2011.

  1. aves911

    Thread Starter New Member

    Jan 12, 2011
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    I've got a circuit I designed that works on the bread board, however when I tried to put it together on a generic PCB board, it no longer works and I cannot seem to trouble shoot it. I'm hoping to find someone or some company that could build my circuit for me so that I can continue assembling my prototype.

    I have all the components, circuit diagram, and pictures of the layout I attempted. If anyone could point me in the right direction it would be a HUGE help!

    Thanks,
    -Jacob
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Care to post a schematic?
     
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    What part of the world are you in and what do you consider reasonable compensation for making the PCB, populating it, and making it work?

    John
     
  4. Wendy

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    Mar 24, 2008
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    I was thinking more in terms of a PCB myself. It is considerably simpler than building one from scratch.
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I'll do it. Prices start at $100 per hour (minimum charge of 2 hours).
    Official quote will be provided when I see a parts list, schematic and the "generic PCB" information
     
  6. aves911

    Thread Starter New Member

    Jan 12, 2011
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    Thanks for the response everyone. I'll throw up a schematic tomorrow morning along with some pictures of the PCB I tried to build (overall dimensions). As for the BOM, I picked up all the parts used from Digi Key for about $10-$15.

    As for location and price, I live in Michigan and up to a few hundred for a tested working circuit would be reasonalbe.

    Thanks,
    -Jacob
     
  7. CDRIVE

    Senior Member

    Jul 1, 2008
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    All forum contract work should transact this smoothly. ;)
     
  8. aves911

    Thread Starter New Member

    Jan 12, 2011
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    I attached the schematic as a .pdf (hand sketch) as well as a few pictures of the board I tried to solder up. For reference, the PCB is about 2" X 1.5" and that's about the max size I have to work with.

    The only real important thing is that the photo sensor is mounted in the middle on the back side of the board and the rest of the components sit on top.

    Also, since I am a beginner at this, I am sure there is room to improve the circuit design itself. The only component I'm really married to is the photosensor as the size/range work very well for my application. Everything else is up in the air as long as it fits on a 2" X 1.5" PCB and the components are shorter (height they stick up from the board) than 0.325".

    I chose to use a relay because I was having issues getting transistors to "switch" on and off properly - probably due to how I had them arranged - but I do need to motor to recieve the full 18V and up to 2A instantaneously, no ramp up.

    And lastly (sorry, haha) If there is room on the board and it is possible, I would like to add a timer circuit that keeps the relay coil (or power transistor) energized for a period of time after to the photosensor is triggered - regardless of what the photosensor outputs during that interval.

    My email is <snip> of anyone interested.

    Thanks,
    -Jacob
     
    Last edited by a moderator: Mar 30, 2011
  9. CDRIVE

    Senior Member

    Jul 1, 2008
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    Typically, the LED portion of an OptoIsolator gets its signal, current, voltage from an isolated source. The way you have it wired here is a bit baffling and makes little sense. It would appear that mcgyvr is going to be doing a bit of circuit design as well manufacture
     
  10. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Is that a reflective photo-coupler? Because of the "ND" at the end of the part# I assumed it was a Digikey part #, but I can't find it. A link? How long of a delay do you want...seconds?...minutes?...?

    Ken
     
  11. aves911

    Thread Starter New Member

    Jan 12, 2011
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  12. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Just a concept at this point....not bench tested (maybe tomorrow). A guess-timate of about 5 seconds delay.

    I'm sure Bill will recommend a 555. ;)

    Ken
     
  13. CDRIVE

    Senior Member

    Jul 1, 2008
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    I must admit I hadn't considered that.
     
  14. debe

    Well-Known Member

    Sep 21, 2010
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    Just wondering if an electrolytic capacitor was put across the relay coil, would it give a delayed time to deactivate?
     
  15. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Unfortunately, it would have to be relativity large, value and size.

    Ken
     
    debe likes this.
  16. Wendy

    Moderator

    Mar 24, 2008
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    Maybe not a 555, but definitely a Schmitt Trigger. Your MOSFET isn't going to switch too cleanly from what I'm seeing. You need a low impedance digital output for its input.

    Come to think of it, a 7555 could do that.
     
  17. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Bill,

    By itself, I agree that the MOSFET doesn't switch like Schmitt trigger with a slow input. But, because relays have different pull-in and drop-out voltages, the MOSFET/relay combination does. I chose the P-MOSFET over a PNP transistor because it makes a better long-period timer...and/or smaller capacitors. My concern is whether the opto output's switching will be relatively "square". Since I don't have Jacob's particular opto, nor know how he is using it, I may not be ably to verify that.

    If he wants the motor to continue to run for a fixed period after the opto initially activates, a 7555 would be better. The MOSFET/relay times-out after the opto's output signal ends.

    I'll take a shot at it, if I have time today.

    Ken
     
  18. aves911

    Thread Starter New Member

    Jan 12, 2011
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    I'm using the sensor in the side of a cylinder shaped object. When something is placed in front of the sensor, it needs to activate the motor long enough to move the the item in an auger type motion back out of cylinder. In my bench testing, the sensor does not respond quickly to fast moving objects. My concern would be that once the item begins to move (quickly) the sensor will no longer pick it up and the motor would stop prematurely. That was the reasoning behind adding a fixed delay. The initial opto output would trigger a timed power cycle for the motor.

    In terms of the output switching, I'm not sure if this helps or not, but when I hooked up the sensor to just powering an LED the brightness of the LED would depend on how far an object was from the sensor. I added a pot to ground on the transistor output to try and make the output more defined as well as create an adjustable "activation distance".
     
  19. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    OK, the test worked with an IR pair, aimed at each other, with the photo-transistor saturating when very briefly unoccluded. The delay on-time was ~2 seconds.

    But, that's not the problem that I now see. If you were to try my common-emitter arrangement (just the 10K load resistor...ignore the delay part) for the opto-coupler, what collector voltages do you see when the cylinder is present at minimum and maximum distances and absent?

    Ken
     
  20. aves911

    Thread Starter New Member

    Jan 12, 2011
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    I'll check tonight for you, thank so for working on this!

    One other question, is it possible for the delay to be adjustable with a pot? A fixed delay would be more than fine but as this is a prototype it would nice to be able to tweek it a bit when doing some performance testing. Just asking as I don't know what's possible/practical.

    Thanks again,
    -Jacob
     
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