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How to stablize the voltage of LPG (Propane) Gas Sensor Module (#27932)? — Parallax Forums

How to stablize the voltage of LPG (Propane) Gas Sensor Module (#27932)?

ladladladladladlad Posts: 6
edited 2012-06-17 00:38 in Accessories
As said in the title, how do i stablize the voltage at TP1 and TP2 , the voltage at tt point keep increasing over time.

Comments

  • ladladladladladlad Posts: 6
    edited 2012-06-12 19:53
    please hlp!!

    and could someone explain tis

    For a 3.3V microcontroller such as the PropellerTM chip, a 3.9 kΩ (10 kΩ could be used) resistor would berequired from the ALR output to the Propeller chip input pin. For the Propeller to control the heater
    switch input (HSW) you would need an NPN switching transistor, such as a 2N3904 and a 1 kΩ resistor.
  • kwinnkwinn Posts: 8,697
    edited 2012-06-12 21:19
    As said in the title, how do i stablize the voltage at TP1 and TP2 , the voltage at tt point keep increasing over time.
    TP1 is the output signal and TP2 is ground. That signal indicates the gas concentration.
    For a 3.3V microcontroller such as the Propeller TM*chip, a 3.9 kΩ*(10 kΩ*could be used) resistor would be required from the ALR output to the Propeller chip input pin.
    The gas sensor runs from 5V so the alarm (ALR) output is 5V. The propeller uses 3.3V so putting 5V directly in to one of it's pins would damage it. A resistor from 3.9K to 10K is needed to prevent damage.
    For the Propeller to control the heater switch input (HSW) you would need an NPN switching transistor, such as a 2N3904 and a 1 kΩ*resistor.
    Adding this transistor and resistor to the circuit allows a microcontroller such as the Propeller to turn the heater on and off as needed.
  • ladladladladladlad Posts: 6
    edited 2012-06-12 23:34
    kwinn wrote: »
    TP1 is the output signal and TP2 is ground. That signal indicates the gas concentration.

    thanks for the reply :), is there anyway to stablize the voltage at TP 1 and TP 2, cause even if there is no gas, the voltage at this point increase significantly.
  • kwinnkwinn Posts: 8,697
    edited 2012-06-13 20:20
    The only thing I can suggest is that you do what the data sheet suggests:

    "As mentioned above R3 allows you to change the span/range of the voltage divider formed by the gas sensor and R3 which is the bottom leg of the divider, electrically speaking. Adjusting R3 to lower values will make the gas sensor less sensitive but more stable. Avoid setting R3 below 200 ohms as at this point you will be close to shorting the output to ground. Setting R3 to higher values will make the gas sensor more responsive, but without a minimum load it will become unstable after a certain point."

    And that you follow the steps and timing of the Basic Stamp demo program in the data sheet.
  • ladladladladladlad Posts: 6
    edited 2012-06-14 23:36
    kwinn wrote: »
    The only thing I can suggest is that you do what the data sheet suggests:

    "As mentioned above R3 allows you to change the span/range of the voltage divider formed by the gas sensor and R3 which is the bottom leg of the divider, electrically speaking. Adjusting R3 to lower values will make the gas sensor less sensitive but more stable. Avoid setting R3 below 200 ohms as at this point you will be close to shorting the output to ground. Setting R3 to higher values will make the gas sensor more responsive, but without a minimum load it will become unstable after a certain point."

    And that you follow the steps and timing of the Basic Stamp demo program in the data sheet.

    thx for the reply, the only problem for me , is that i do not have a basic stamp module to do it, i only have the sensor module and a msp430.
  • kwinnkwinn Posts: 8,697
    edited 2012-06-17 00:38
    ladladlad wrote: »
    thx for the reply, the only problem for me , is that i do not have a basic stamp module to do it, i only have the sensor module and a msp430.

    You don't really need a basic stamp to do this. You can use the basic program steps as a guide to create a similar program for the msp430 or any other microcontroller.
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