Fuel control

Discussion in 'The Projects Forum' started by chandu13, Oct 15, 2008.

  1. chandu13

    Thread Starter Member

    Oct 15, 2008
    22
    0
    Hay

    I need project help,I have to control the gas fuel control using proportional solenoid valve.
    I am using 1KHz PWM signal, TIP122 driver transistor & 1N4007 diode across the load for driving the proportional solenoid,Still am facing hystersis problem because of the back EMF.

    how to reduce hystersis problem to get constant gas flow for constant volatge using proportinal valve & how to nullify the back EMF

    Regards
    chandu
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    How much current is going through the TIP122?

    1N4007 rectifiers are rated for an average current of 1.0A, and have a Vf of 1.1V at that current. They are also slow to switch on and off.

    Try using Schottky diodes with a higher current rating, lower voltage rating.
     
  3. chandu13

    Thread Starter Member

    Oct 15, 2008
    22
    0
    Thanks for reply

    I am facing problem with proportional solenoid
    This is the data sheet of the valve http://www.dwyer-inst.com/PDF_files/SVP_iom.pdf
    In the data sheet he has not mentioned solenoid valve frequency range
    Whenever I used 1KHz PWM signal I am facing more histersis but no noise
    Whenever I used 100Hz PWM signal, histersis has reduced but valve is making noise
    Normally what will be the frequency range of proportional solenoid valves?
    Please need the suggestions & help

    Regards

    chandu
     
  4. raybo

    Member

    Oct 18, 2008
    22
    0
    I asume car 12v system depends on the ratios of the coils I imagine hi EMF a scottkey diode are faster and lower voltage drop also do not have the reverse breakdown probably reqiered so who knows. why voltage why not current control same control without the effects. but for the back EMF try an active clamp like and SCR.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    It wasn't necessary for them to specify a frequency range, since they specify the input signal to be from 0 to 24 volts DC, with a maximum current of 400mA.

    If you want to control it using PWM, I suggest that you need to insert an LC filter between your PWM generator and the solenoid; basically a buck regulator with a capacitor.
     
  6. chandu13

    Thread Starter Member

    Oct 15, 2008
    22
    0
    Hay

    Please suggest how to control the proportional solenoid valve for better control
    Shell I use direct DC voltage or DC voltage derived from the PWM signal using low pass filters
    What is the difference between DC voltage and DC voltage derived from the PWM signal using low pass filters?
    If I use DC voltage can I face back EMF problems?
    Please can you provide driver circuits for proportional solenoid valve or related site information

    Regards
    chandu
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If you read the data about the valve, you will understand that the valve is meant to be controlled with a DC voltage, not PWM. That is not going to be a successful approach.

    The valve opens proportionally to the magnitude of a DC voltage in the range of 0 - 24 volts applied to it.
     
  8. chandu13

    Thread Starter Member

    Oct 15, 2008
    22
    0
    Hay

    I have tested DC voltage in the range of 0 - 24 volts applied to proportional solenoid valve. Whenever I applied DC voltage to the solenoid I am facing the hystersis Problem. I kept diode across the load but am facing same problem.

    Regards
    chandu
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    How can you be having a problem with hysteresis when operating the valve with DC? As you increase the voltage, the valve should open more and more. It should hold the degree of open if the voltage is held constant. It is not meant to to be controlled with PWM.
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    What kind of gas are you controlling? Are you certain you don't have some sort of contamination (dirt, etc.) in the solenoid?
     
  11. chandu13

    Thread Starter Member

    Oct 15, 2008
    22
    0
    Hai

    I have tested proportional solenoid using variable power supply
    For testing I connected one end of the proportional valve to the 15-PSI constant pressure(air compressor) and one more end connected to the air rota meter range is 0-8LPM
    By supply the variable voltage (variable DC power supply) to the proportional valve I am measuring the flow rate using air rotometer.

    Vlotage Downscale (LPM) upscale (LPM)
    5.0V -----------0 --------------0
    5.5v -----------0-------------- 0
    6.0v -----------0-------------- 0
    6.5v -----------0-------------- 0.2
    7.0v -----------0-------------- 0.3
    7.5v -----------0.1 ------------0.4
    8.0v -----------0.3 ------------0.6
    8.5v -----------0.4 ------------1.3
    9.0v -----------0.8 ------------2.0
    9.5v -----------1.5 ------------2.6
    10.0v ----------2.4 ------------3.1
    10.5v ----------3.3-------------3.5
    11.0v ----------3.7-------------3.7

    Down scale reading I have taken while increasing the voltage from 5v-11v
    Up scale reading I have taken while decreasing the voltage from 11v-5v

    Ex: for 9.5v 1.5 2.6 error is 1.1

    I am facing this problem while using DC voltage

    Regards
    chandu
     
  12. beenthere

    Retired Moderator

    Apr 20, 2004
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    What happens if you go through the voltages up to the full 24?
     
  13. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Does your compressor have an air filter on the output? Solid particulates would probably cause what you are describing.
     
  14. chandu13

    Thread Starter Member

    Oct 15, 2008
    22
    0
    Hay

    Iam oprating solinide 0-12V ofter 12V the value will be saturate acording to the service manuval graph
    Iam using the filter on the output compressor & kept pressure 15 PSI constant

    Just I thinking in this way

    When ever I apllied DC volatge:
    current flows through coil, a magnetic field is set up around the coil when ever I incerse the voltage or decrese the volatge the back EMF is creating
    The back EMF will prasent in the coil and casing hystersis problams.how the back EMF will nullfi in the DC voltage

    When ever I apllied PWM signal:
    current flows through coil in the high pulse(1), a magnetic field is set up around the coil , the electric current will switched off in the low pulse (0), the magnetic field around the coil collapses through the diode

    Regards
    chandu
     
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