need help ASAP for science fair

Discussion in 'The Projects Forum' started by khadeejabaqui, Feb 21, 2016.

  1. khadeejabaqui

    Thread Starter New Member

    Jan 25, 2016
    9
    0
    HI
    We were able to successfully complete this project. We have Science fair on Monday.When we did the last trial ,we realised that the pump starts without the conductivity sensor and Potentiometer,and the pump does not stop.After troubleshooting we could concluded that MOSFET may be shorted so we replaced it.IN Radio shack we could only find LM317T and 7812.We are not clear about the terminals .
    http://www.sciencebuddies.org/science-f ... p040.shtml
    The circuit did not work with first MOSFET.With the second MOSFET we tried our best guess for the terminals.The pumped was initially off.After adjusting the potentionmteter,we could normalized by placing both tubes in vinegar.The main problem is after putting the pipes in baking soda and vinegar,the pump did not start by itself in order for baking soda to flow in vinegar to neutralize the solution.Also based on the terminals we guessed ,we also changed the connection based on S,D, and G.
    Its due Monday.We can not demonstrate like this.Please help us.Its not possible for us to get same MOSFET at such short notice.Please guide us with the MOSFET terminals and why we are not getting the results.How should we manage ?Also I think we need help with the concept of conductivity sensor.What else can we change?
    Please help us ASAP.
     
  2. Ramussons

    Active Member

    May 3, 2013
    557
    92
    I don't think anybody can give any advice without a schematic :(
     
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    I don't understand, you clearly have access to the internet, so why are you guessing pin-outs? You know that LM317T and 7812 are not Mosfets?
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    As said the LM317 and 7812 are not mosfets but voltage regulators.
    Show us the schematic and the numbers of the intended mosfet.

    I looked at the procedure on the give page:
    http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBio_p040.shtml#procedure
    I have the idea that the design is not really good.
    The mosfet can stay in linear mode and become hot, as no heatsink is used on the given page.
    The mosfet type can be found on the materials page:
    http://www.sciencebuddies.org/science-fair-projects/project_ideas/HumBio_p040.shtml#materials


    ALWAYS look in the datasheet when you are using components.
    The STP16NF06L (as given in the material list) has the following connections:

    STP16NF06L_shortdata.png

    I found an older thread with the same project:
    http://forum.allaboutcircuits.com/threads/artificial-pancreas.119444/

    In there you can also find a schematic.

    Bertus
     
  5. khadeejabaqui

    Thread Starter New Member

    Jan 25, 2016
    9
    0
    Can anyone please help me locate the same products on Fry's.There are so many similar products.I could not distinguish between them.I wold really appreciate the help.
    Thanks
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    I have looked at frys, but they seem to sell the horrible NTE components.
    NTE does not make the components themselves, but rebrands some from other companies.
    A lot of times the specs are off, as the sell a NTE part for a whole series of numbers of the other companies.

    Better find a store that sells REAL components.

    Bertus
     
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