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Looking to outsource schematic design. — Parallax Forums

Looking to outsource schematic design.

computer guycomputer guy Posts: 1,113
edited 2012-05-18 22:24 in General Discussion
Hello Everyone,

It has been a while since I have posted on the Parallax forums, so many of you may not know me.

I have been concentrating more on my second passion (software development) and recently the need for some hardware has come up.
In simple terms what I need is a circuit and related spin/asm code that can monitor the volume of liquid in a clear bag (sensors can be mounted to the outside of the bag, but not the inside).
The volume level then needs to be sent over bluetooth to a paired device.

The entire thing needs to be as small as humanly possible so try to design with smd components in mind.

I am willing to pay for any components used for prototyping and for time.

The plan is to then test your solution and if it meets my requirements, produce it.

Budget is $500AUD.



Kind regards,
Anthony Myatt
www.anthonymyatt.net

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-05-18 07:06
    Setting aside the micro-controller and sensor aspects, there is some physical construction involved. With that in mind, the question is how much volume - 10ml or 10 liters? And at what level of error tolerance? Will the material be a gas, a liquid, or some sort of bulk solid?

    At the end of the day without more details, one could waste quite a bit of time working on something that is absolutely useless to you.

    Occasionally we get request here for something that the developer really doesn't want to disclose much about. If that is your concern, you might just seek people that are willing to sign a proper non-disclosure agreement and you have a resume of past successes. There is really no reason to have to discuss the project in detail on this forum.
  • computer guycomputer guy Posts: 1,113
    edited 2012-05-18 08:14
    Loopy Byteloose wrote: »
    Setting aside the micro-controller and sensor aspects, there is some physical construction involved. With that in mind, the question is how much volume - 10ml or 10 liters? And at what level of error tolerance? Will the material be a gas, a liquid, or some sort of bulk solid?

    At the end of the day without more details, one could waste quite a bit of time working on something that is absolutely useless to you.

    Occasionally we get request here for something that the developer really doesn't want to disclose much about. If that is your concern, you might just seek people that are willing to sign a proper non-disclosure agreement and you have a resume of past successes. There is really no reason to have to discuss the project in detail on this forum.

    Thank you for your reply.

    The bag has a maximum volume of 750mL.
    The sensor really only NEEDS to tell if the bag is full but some increments between empty and full would be nice.
    It will be a liquid that varies from clear to dark yellow.

    If anyone shows a great deal of interest I would be more than happy to provide more details after a NDA is signed.
  • FranklinFranklin Posts: 4,747
    edited 2012-05-18 10:00
    I've seen in either N&V or Circuit Cellar a cap sense sensor for a drink bladder in a pack. They used foil on the outside to get the readings.
  • kwinnkwinn Posts: 8,697
    edited 2012-05-18 11:03
    If this is similar to an IV bag or milk bag on an automated fill line you could use one or more load cells to weigh the contents. If liquids of different densities are bagged then density must be taken into account.
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-05-18 12:19
    Or measure mass by vibrating it and measure either frequency or acceleration.

    Duane J
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2012-05-18 16:16
    It will be a liquid that varies from clear to dark yellow. The bag has a maximum volume of 750mL.

    Can you weigh your urine collection bag?

    If so, one can think of a small box with hooks on either end and a load cell inside, plus battery, electronics etc.

    I'm struggling to think of other sensors that would work besides weight. I'll ponder this some more.
  • xanaduxanadu Posts: 3,347
    edited 2012-05-18 16:41
    You could possibly use a hall effect sensor opposite a magnet, and some basic analog circuit with an output to an LED or Spk.

    I'm thinking make a bag for the bag to go into, and mount everything inside the external bag.
  • computer guycomputer guy Posts: 1,113
    edited 2012-05-18 18:31
    For arguments sake, lets say this is a camel pack. (I will provide actual details once someone has accepted the project).
    The bag can not be weighed as it is wearable.

    The bag expands when filled.

    The capacitance idea and hall effect sensor sound like good ideas. Can anyone prove the concept though?

    I'm putting this out for tender.

    If you have an idea, please PM me with:

    1. How you plan to do it
    2. Any testing you have done with your idea
    3. How much you want to complete the project from idea to working prototype


    -Anthony
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-05-18 19:30
    Hi Anthony;

    A 2 plate capacitor basically flexible and one on each side of the bag
    can be used to measure the volume in the bag.

    The capacitance between the plates is dependent on the spacing along with the
    dielectric constant of the stuff, presumably an aqueous based liquid, in the bag.
    This will need some calibration to be reasonably accurate.

    The Prop can measure capacitance quite accurately.

    BTW, $500 doesn't even come close to the cost of the circuit design, PC-board design,
    software, and regulatory requirements for a fully fledged commercial design. Sorry %^(

    If it's a "Medical" product the cost is several times higher.
    If it's a "Life Rated" product the cost is a lot more, if Parallax will even allow you to use their parts.

    Duane J
  • frank freedmanfrank freedman Posts: 1,983
    edited 2012-05-18 20:14
    What do you define as full? Just a predefined level in the bag or a level and a maximum predetermined level? I will send you an idea if you can provide this detail.

    FF
  • computer guycomputer guy Posts: 1,113
    edited 2012-05-18 20:24
    frank freedman wrote: »
    What do you define as full? Just a predefined level in the bag or a level and a maximum predetermined level? I will send you an idea if you can provide this detail.

    FF

    The bag holds about 1 litre, but 750mL is "full". So it needs to sense that it is at or above 750mL and then when it has dropped below this level again.
    Duane C. Johnson wrote: »
    Hi Anthony;

    A 2 plate capacitor basically flexible and one on each side of the bag
    can be used to measure the volume in the bag.

    The capacitance between the plates is dependent on the spacing along with the
    dielectric constant of the stuff, presumably an aqueous based liquid, in the bag.
    This will need some calibration to be reasonably accurate.

    The Prop can measure capacitance quite accurately.

    BTW, $500 doesn't even come close to the cost of the circuit design, PC-board design,
    software, and regulatory requirements for a fully fledged commercial design. Sorry %^(

    If it's a "Medical" product the cost is several times higher.
    If it's a "Life Rated" product the cost is a lot more, if Parallax will even allow you to use their parts.

    Duane J

    I am more than happy to go over the $500 budget if someone can provide a solution and a reasonable price.
    I am after schematic, software and working prototype only. PCB design and regulatory requirements/licensing I can do.

    From previous projects I believe the prototyping can be done for around $250 or less in parts.
  • FranklinFranklin Posts: 4,747
    edited 2012-05-18 21:29
    The article I was referring to was Circuit Cellar issue 164 (Mar 2004) page 28.by Richard Wotiz.
  • computer guycomputer guy Posts: 1,113
    edited 2012-05-18 22:24
    Hello Franklin,

    I couldn't find a digital copy of the article but I did manage to find his notes.
    An interesting design and a possible solution.
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