proportional amplifier to control dc valve

Discussion in 'General Electronics Chat' started by mah, Dec 28, 2014.

  1. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    i want your ideas to do a circuit that amplify input signal 0-10 V to 5-24 v to control a 24 v proportional dc valve

    Mod edit: The Completed Projects Forum is for Completed Projects only. It is meant to allow members to show plans for projects they built so other members can duplicate them if desired. New threads are also automatically moderated per Moderator review for this reason. Your thread does not belong in this forum, and was moved here.
     
    Last edited by a moderator: Dec 28, 2014
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,542
    2,369
    What current is the valve coil?
    Max.
     
  3. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    1.5 Amp is the max.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,542
    2,369
    I would look at using something like the OPA551, it is good for ±30v swing at 300ma so you would need a NPN/PNP push-pull output to drive the valve.
    Max.
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Or you can use one of the high-current opamps from here.
     
  6. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    oh GOD up to 50A it must be very expensive type of opamp.
     
  7. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    but why should i use this type of opamp? why couldn't use it to drive mosfet that could hold high current instead of opamp?
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    You didn't look far enough down the page. Apex sells some 3A ones.

    In a previous life, I bought hundreds of that type of opamp from Apex.
     
  9. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    excuse me ,
    excuse me,i don't get you
     
  10. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Look up PA74, PA74A, PA75, or PA76 on the Apex web site.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,542
    2,369
    TI will send you a couple free samples of OPA551!
    Max.
     
  12. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    Last edited: Dec 28, 2014
  13. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    but the npn /pnp can't drive 1 A to the valve.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,542
    2,369
    I meant a couple of discrete bi-polar devices to increase the output capacity.
    Max.
     
  15. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    what do you mean by a couple? how to do it ? would you clarify with a picture?
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,542
    2,369
    Like so.
    upload_2014-12-28_13-27-11.png

    Max.
     
  17. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    The normal way of controlling this kind of valve is to drive it with a current that is proportional to the input control voltage, not a voltage proportional to the input.
     
  18. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    this will operate as a voltage follower. when there is positve output the npn will work and connects +v to the valve then 1A passed and blow up the npn
     
  19. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,542
    2,369
    That is basically the method I used in #16, in CNC applications where ±10vdc analogue is the source.
    Feedback via encoder.
    The circuit shown has been around for a long time used in EDM machines etc.
    You can limit the maximum freq by resistor in the collectors if needed, or on the output.
    Max.
     
    Last edited: Dec 28, 2014
  20. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    did you see the operation in the link ? i want to do something like this.i don't mind to do it with current but also the valve shouldn't mind
     
Loading...