Science Fair Help - Sensors....

Discussion in 'Homework Help' started by andr3co4, Feb 12, 2013.

  1. andr3co4

    Thread Starter New Member

    Feb 12, 2013
    Hey guys i am new to this forum and i am a complete noob in electronics and hoped if i could find some info on how to do this science fair project.
    It is basically an ice detector and uses some simple stuff. Instead I want to make it a water detector that is attached to a mobility cane so it serves as an water detector for the blind to avoid mishaps in places just after the rain or rather puddles that show up due to car washes etc etc. I just have got a mobility cane. I hope you guys can tell me alternative circuits and components which are much easier to find.
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    The thing is that i have a hard time finding this stuff and wasted all my time searching for components and i also dont understand a thing about electronics but i am very interested. My project is due next week and i live in the UAE but i have to go to Abu Dhabi which is the nearest city to find components and i live 200 km away and since the shops are closed on Friday I gotta go on Saturday to get the components and do it over night and it is due next Sunday.
    My teacher said that i need a multimeter to calibrate the sensor to find the certain reference voltage and then tweak the comparator until i find the perfect balance. But since i am a noob i dont understand a thing and i have no idea how to present it.Presentation is not much of a worry. but I dont know how the circuit works
    I cannot do anything until Saturday.
    Much help is needed here and fast....I hope i dont come off as a dumb idiot here...
    BTW Radioshack in the UAE seems to be closed since a year....
  2. andr3co4

    Thread Starter New Member

    Feb 12, 2013
    K...I specified down to the things i need help with rather than u guys figuring out for me...
    1. I need help if there are any alternatives to the components that are easier to find...
    2.The items are LM324 comparator chip....a A2TPMI334 thermophile sensor and a piezzo buzzer....and a circuit board and banana wires....My teacher told me to calibrate the voltage for the he told me to connect the multimeter to the sensor and find the minimum measurements or the average measurements measuring water and then a dry object countless times Once found the reference voltage (correct term i believe?) and then play around with the comparator until i find the sweet spot which allows the current to pass through since this comparator is also an amplifier ....the current is boosted to over 2.5 volts i believe and then sent to the buzzer which beeps if the current is over 2.5 volts but doesnt respond if it is less than that....My question is that how do i tweak the voltage as the comparator chip doesnt seem to have a knob or some sort to tweak it.....
    My last question as of now is how do i put it together...i mean do i have to add any resistors or any components in between? Do i use the banana cords to connect the sensor to the comparator etc..
    I may ask more questions as soon as they pop up in my brain
    Thanks in advance and i am sorry for the long read...:)
    PS I am 13 years old and in middle school....if you guys can help me to something that is of my level
  3. WBahn


    Mar 31, 2012
    The LM324 is not a comparator, it is an operational amplifier. You may be using it as a comparator and it may work well enough for your needs, but keep in mind that a true comparator may work better if it turns out the LM324 isn't good enough.

    It sounds like you are asking us to design your circuit for you. At only 13 years old, that may not be too unreasonable, but is that considered acceptable for entry as YOUR project into a competitive science fair?

    How is it that you are expecting/hoping that an infrared temperature sensor is going to be able to distinguish between wet and not wet? Where did the notion of using a thermopille sensor come from? How do you plan to program the sensor (this is a pretty sophisticated sensor and has on-board digital signal processing capabilities)?

    I don't know how successful you can hope your project to be given that you really haven't started and you have less than a week to bring it all together. But, do the best you can and even if it doesn't go well you will learn a lot of valuable things.

    Best of luck!
    andr3co4 likes this.
  4. andr3co4

    Thread Starter New Member

    Feb 12, 2013
    Yes you are right i cant ask u guys for my science fair project...thats all fair..btw i did find the circuit....but the only help i need is that is it possible to change the purpose of the sensor from ice to water....Thanks so much for your reply ....:)
  5. t06afre

    AAC Fanatic!

    May 11, 2009
    Well we may give you some pointers in your project. As start post your circuit diagram.
  6. andr3co4

    Thread Starter New Member

    Feb 12, 2013