Squelch control for a "baby monitoring" device

Discussion in 'Wireless & RF Design' started by Steve S., Dec 8, 2014.

  1. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    I am interested in finding a tech who can create a schematic incorporating a squelch control in the hand held unit of a common baby monitoring device.
    Thanks,
    Steve
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    find the number of the detector chip used in the monitor, most have a pin for use in squelch circuit.
     
  3. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    Would you be interested in talking further about my project? My email address is stevesink@gmail.com
     
  4. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    I should have been more specific in my first post. I am looking for someone I can pay to help with this project.
    Thanks,
    Steve
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    You might want to remove your email address and request that some one contact you through the private message system in the allaboutcircuits system
     
  6. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    Thanks. As you might have guessed I am new to this.
     
  7. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    Will do once I figure out how to do that
     
  8. ScottWang

    Moderator

    Aug 23, 2012
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    Move to the 3# and using edit button to delete the email address.
     
  9. Papabravo

    Expert

    Feb 24, 2006
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    It would be cheaper to buy the unit that you need. Expect to pay a competent tech at least $35/hr if he has the right equipment. Shoehorning additional circuitry into an existing unit is not a surefire proposition. On top of that it is incredibly easy to damage a board beyond repair and then you'll end up buying a new unit anyway. You should also be aware that over all the years and all the posts there are virtually no stories where an offer to pay resulted in actual work being done and payments received. If there are they are not talking.
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    The main problem with modifying and improving an existing low cost consumer device is that you cannot afford to compete with a company that has already made a significant capital investment in custom chips, custom PC board, and custom injection molded plastic packages. To protect their market share they will sue you at the drop of a hat just to protect their market. You cannot get a company off the ground and defend yourself in court simultaneously.

    I have over 25 years experience in low volume manufacturing for the industrial sector. The cheapest product we ever sold had a retail price of $110.00 and we sold direct to the customer. We designed the PCB, we wrote the firmware, we designed the packaging, and we did final assembly and test. Our biggest expense after component costs was PCB fabrication and assembly. The product we sold for $110.00 had $20.00 in components, $12.00 in PCB fab, and $15.00 in assembly cost for 100 unit lots. We never got rich even though we used a multiplier of 2.5 burdened material cost.

    Making and selling hundreds of something that retails for $10.00 cannot be done profitably. Of course if you have a small fortune and your aim is to dissipate it then by all means -- knock yourself out.
     
    Last edited: Dec 10, 2014
    absf likes this.
  11. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    I certainly appreciate your time and effort on my behalf.

    Your advice and experience has saved me a substantial amount of money.

    Thanks,
    Steve
     
  12. Papabravo

    Expert

    Feb 24, 2006
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    I sometimes feel bad about throwing cold water on people's plans and ideas. The one bit of encouragement I can offer is that there is comparatively little value in a single idea; however there is a vast store of value in a string of ideas. The only way to monetize the value of a string of ideas is to start a company, funded out of your pocket if necessary, and build it slowly by building a few and selling a few.

    Oh...and don't quit your day job until you have a winner.
     
    absf likes this.
  13. alfacliff

    Well-Known Member

    Dec 13, 2013
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    many of the baby monitors operate on the same frequencies and modes used on scanners, try to find a scanner that will work with your baby monitor transmitter. also, baby monitors usually transmit all the time, so a squelch would probably not work with one.
     
  14. Papabravo

    Expert

    Feb 24, 2006
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    That's an excellent point. Most squelch gates operate by detecting the carrier, not the information encoded in the modulation method. If the carrier is on all the time then more sophisticated methods are required to achieve the required function.
     
  15. alfacliff

    Well-Known Member

    Dec 13, 2013
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    and fm recievers use a noise based squelch, a carrier quiets the background noise generated by an fm detector.
     
  16. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    Thanks guys.

    My intention was to leave the "sending unit" in the on position. There will be continuos collateral noise in this location. The "receiving unit"would "tone out" this noise using an adjustable squelch knob. When the event to be monitored activated it would generate a louder noise overriding the squelch control and notify the "receiving unit" via speaker the sound generated by the event mechanism. To far fetched? Have I broken all the rules of electronics?
     
  17. Papabravo

    Expert

    Feb 24, 2006
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    You mean by quieting, that the incoming signal, a modulated carrier, swamps any noise in the receiver's passband.
     
  18. Papabravo

    Expert

    Feb 24, 2006
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    No, I don't think so. You've just asked a series of questions to determine the feasibility of an idea. You haven't stepped in anything yet.
    RF or Radio Frequency devices use a variety of methods to combine an information signal with a carrier signal in a transmitter. In the receiver there are circuits that recover a replica of the information signal. Each of the methods has advantages and disadvantages.

    Baby monitors, public service radios, and VHF amateur radios use a method called FM for Frequency Modulation. You can read more about it here:

    http://en.wikipedia.org/wiki/Frequency_modulation
     
  19. Steve S.

    Thread Starter New Member

    Dec 8, 2014
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    I will read and continue my education in this field.

    I am semi retired and look forward to learning something new.
     
  20. Papabravo

    Expert

    Feb 24, 2006
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    I'd be interested to know if you find one with the feature you're looking for.
     
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