Hydrogen Gas Sensor Circuit

Discussion in 'The Projects Forum' started by varsity_villain, Aug 11, 2008.

  1. varsity_villain

    varsity_villain Thread Starter New Member

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    Hi all,
    I wan to design an analog circuit which can detect the concentration of the hydrogen and display it in LCD. the idea of the circuit is, it will detect an input from a gas sensor and the input will be used to calculate the concentration of the gas and will show the output in LCD.
    So i need to design the circuit where it can detect the input from sensor. I dnt know how to start design the circuit. Anyone can help on this?? Any suggested analog circuit diagram???

    realy need ur help guyz....
  2. jpanhalt

    jpanhalt E-book Developer

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    Is the hydrogen mixed with other gases? Which gases? What concentrations of hydrogen do you need to detect? What pressures?

    In other words, you need to give more information about the conditions in which it will be operating.

    Have you done any search yourself for information? Commercial units are readily available. Here and here are just two of many found under "hydrogen detector."

    Also, Wikipedia has a nice article on hydrogen detection.

    What is your level of experience in electronics and microcontroller programming?

    John
  3. kender

    kender Active Member

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    If you've identified the sensor, whose output you need to measure, could you post a link to its datasheet? To help you design a circuit, we need to know the sensor that you have.
    Last edited: Sep 3, 2008
  4. kammenos

    kammenos Active Member

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    Sensor -> microcontroller -> LCD...

    Simple answer for simple question. Please be more specific
  5. varsity_villain

    varsity_villain Thread Starter New Member

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    The idea of the design is

    sensor > analog circuit > lcd

    analog circuit:
    input > integrator stage > comparator stage > output

    so i have to design the analog circuit with the idea given to me. the sensor should only detect hydrogen gas and send the input as voltage to analog circuit. since the sensor will be fabricated by another group so i dont know the datasheet of the sensor. Basically the sensor is fabricated using SnO2 material. So any suggestion on how i can start design the analog circuit???
  6. blocco a spirale

    blocco a spirale Active Member

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    You've got to know the specs of the sensor.

    What output voltage range are we looking at? microvolts? Volts? offset? How does the output relate to the concentration of gas?
  7. thingmaker3

    thingmaker3 Retired Moderator

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    If you at least know the required range of your display, you can work on a display driver. Once the stats on the sensor are available, you can design the signal conditioner.

    If you don't know the required range of the display, you'll be able to work on something else entirely until your other group can give you some numbers.
  8. varsity_villain

    varsity_villain Thread Starter New Member

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    hi,
    is there anyone can suggest any circuit that i can construct to test the concentration of the hydrogen?? so far i found a light integrator circuit as my reference. do u think i can use light integrator circuit diagram to construct hydrogen circuit???
    after had discussion with the group who will fabricate the hydrogen sensor, they said the output which can be produce from sensor is in mvolt or micro volt. so they wan my analog circuit can amplify the output and determine the concentration.

    how i can construct the circuit?? from my understanding, i think i can use op-amp 741 as integrator and as a comparator. i juz dont understand how i wan use the op-amp with other components to came out with the analog circuit.

    from,
    confused...
    Last edited: Nov 12, 2008
  9. thingmaker3

    thingmaker3 Retired Moderator

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    The 741 is a relatively old amp. You may be disappointed with its performance.

    If you want a dual supply op amp, consider the TL084. If you want a single supply op amp, consider the OPA377.

    Many other choices are available as well.

    This might be of help: http://www.allaboutcircuits.com/vol_3/chpt_8/index.html
  10. varsity_villain

    varsity_villain Thread Starter New Member

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    ok, if i wan to construct the circuit i need a reference. can u suggest any circuit diagram or tutorial were i can learn to build the analog circuit. i dont know from where to start. any suggestion please?
  11. jpanhalt

    jpanhalt E-book Developer

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    You have yet to say whether any other gases are present and which ones. If it is pure hydrogen, all you need to do is monitor pressure and temperature to know concentration in moles/liter.

    John
  12. Papabravo

    Papabravo AAC Fanatic!

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    I would recommend that you start by reading the datasheet for the TL084

    http://focus.ti.com/lit/ds/symlink/tl084.pdf

    Then I would peruse the TI website for application notes like

    http://focus.ti.com/lit/an/sloa020a/sloa020a.pdf

    Lastly you probably need a college level textbook on analog design

    http://www.amazon.com/Analog-Circui...=sr_1_1?ie=UTF8&s=books&qid=1226762321&sr=1-1

    http://www.amazon.com/Analog-Circui...=sr_1_1?ie=UTF8&s=books&qid=1226762321&sr=1-1

    You might also want to give some thought to doing a better job of defining your requirments. We cannot just trot out a circuit because the number of possibilities certainly exceeds Graham's number. The only way to reduce the number of possibilities is to refine your requirements so that candidate circuits can be evaluated against those requirements.
  13. thingmaker3

    thingmaker3 Retired Moderator

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    The input is still unspecified. "Millivolts or microvolts" is not a specification.

    If you don't know your expected input range, and won't tell your expected output range, no one in the universe can help you.
  14. Bernard

    Bernard Senior Member

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    Figaro Engineering of Japan makes a line of oxidizable gas sensors. Output voltages[AC or DC ] with a 4k load resistor run from 0 to 50 V with 100V supply, at an H2 consintration of 3000 PPM.They require a lo V heater supply.
  15. varsity_villain

    varsity_villain Thread Starter New Member

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  16. varsity_villain

    varsity_villain Thread Starter New Member

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    can i use this circuit to test the hydrogen gas concentraton?? please guide me more to construct more reliable circuit. 10q.
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