Making a voltage sensor to drive a linear solenoid.

Discussion in 'General Electronics Chat' started by russ079, Apr 10, 2016.

  1. russ079

    Thread Starter New Member

    Apr 10, 2016
    4
    0
    Hiya, Im a newbie and after some help. My electronic knowledge is very limited. Basically Ive got a 25kva generator that was designed to run off the pto shaft on a tractor. Ive made it into a stand alone unit with a engine on. What Im after is a board to control to the throttle on the diesel pump.Basically Ive set to engine to run at 1500rpm and the generator makes 415v , and it powers up to about 12kva fine. But when drawing higher current it labours the engine, slightly lowering the revs and only making 350v. A small increase on on the throttle brings it back to 415v.

    What I need is a board to sense the voltage from the generator either single phase or 3 - 240v or 415v, and to be able to set a desired voltage within a threshold maybe +/- 5v. And then the board drives a linear actuator, to move the throttle arm forward and back slightly to keep the correct voltage. It would be nice if it sensed over voltage, and cut the circuit to the diesel solenoid, so it kills the engine if anything went wrong. Ideally all to work off 12v dc so I could power it from the engines battery.

    Any helps or ideas to achieve this would be greatly appreciated. If someone is willing to build me one, Id be happy to buy it off them.

    Thanks
    Russ
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,773
    1,103
    Does the generator also have a low-voltage output (e.g. 12V, 24V)? If so, it might be easier/safer to monitor that.
     
  3. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,004
    1,523
    Doesn't your engine have a governor on it? Or is it out of a car or truck.
     
  4. russ079

    Thread Starter New Member

    Apr 10, 2016
    4
    0
    The engine is out a landrover, the generator does have a green lamp on it for indicating correct voltage I'll test that to see what it is. Cheers
     
  5. russ079

    Thread Starter New Member

    Apr 10, 2016
    4
    0
    Tested the green light for correct voltage earlier and it was 5.2v
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,004
    1,523
    Never done what your wanting, but this is how I would try to do it. A window comparator using the voltage from the "green light" as Vin. With a corresponding higher and lower voltage for the reference voltages. Also a linear stepper motor instead of a linear actuator. The linear stepper is easier to control position with, because it moves in smaller increments than a linear actuator. The throttle control shouldn't need to move in a large swing of movement, to control the RPM's. There are many inexpensive stepper drivers on Ebay that would also be needed. Or you could adapt a mechanical governor from a tractor or other diesel engine to your engine.

    A link to one brand of linear stepper. Don't be scared of the prices, Ebay has them less expensive. http://www.haydonkerk.com/LinearActuatorProducts/StepperMotorLinearActuators/tabid/66/Default.aspx
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,773
    1,103
    Does that voltage vary proportionally with engine rpm?
     
    shortbus likes this.
  8. russ079

    Thread Starter New Member

    Apr 10, 2016
    4
    0
    Yes the voltage is proportional to the engine rpm. Thats why when the engines loaded i need to keep the revs constant.

    Thanks shortbus, that was very helpful. Ive ordered a stepper motor and driver. I looked at comparators but all ones on ebay were 2/3 weeks wait from Hong Kong. Ive found a simple circuit that works that works similar to the comparator, So going to pick up the bits and try to control the stepper from the output for the 3 lights.

    http://electronicsproject.org/ac-mains-voltage-indicator/
     
  9. crutschow

    Expert

    Mar 14, 2008
    12,991
    3,227
    What stepper motor and driver did you order?
     
  10. MrSoftware

    Member

    Oct 29, 2013
    497
    122
    Instead of watching the voltage, what if you watched the engine RPM instead? This will keep your frequency right, and if the frequency is good but the voltage sags a lot then the generator is probably overloaded. You might be able to use a sensor on the shaft, such as a hall effect sensor, and an arduino to count the shaft frequency. The same arduino could control a servo that controls the throttle. Now you can make adjustments to how it works in code.
     
Loading...