Making a voltage sensor to drive a linear solenoid.

Thread Starter

russ079

Joined Apr 10, 2016
4
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
 

Alec_t

Joined Sep 17, 2013
14,263
Does the generator also have a low-voltage output (e.g. 12V, 24V)? If so, it might be easier/safer to monitor that.
 

Thread Starter

russ079

Joined Apr 10, 2016
4
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
 

shortbus

Joined Sep 30, 2009
10,045
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
 

Thread Starter

russ079

Joined Apr 10, 2016
4
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/
 

MrSoftware

Joined Oct 29, 2013
2,186
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.
 
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