Hey guys,
I am working on a project which is a load controller for a water turbine in stand-alone operation.
When the regular load is to low or the river is to fast, there is a power surplus which has to be dissipated. That's where the lamp comes in.
The microcontroller realizes that too much power is available and gives a signal to the mosfet to switch on. The power supply is realized by a capacitive power supply.
The problem is following: When I give a high signal (5V) to the Mosfet and it turns on the way it should. But if the signal is low (0V) the mosfet does not turn off. Instead the lamp is shining less bright. Even if put out the cable from the µC to the mosfet and hold it to the source/ground the light doesn't turn off.
When I put the grounds of the mosfet (at source and the ground at the 1k resistor) to a separate "ground 2" the mosfet shows the same behaviour BUT now I can remove the signal from the µC and the lamp is totally off.
The mosfet is working properly by the way. When test it all alone with a different ground it is working.
I think it has something to do with the grounds but when I measure the signal based on the ground with a differential probe on the oscilloscope, then there is the right signal at the mosfet.
My question is: Why does the mosfet behave like this and how can I make it work properly?
Sorry for my grammar, I am from germany
I am working on a project which is a load controller for a water turbine in stand-alone operation.
When the regular load is to low or the river is to fast, there is a power surplus which has to be dissipated. That's where the lamp comes in.
The microcontroller realizes that too much power is available and gives a signal to the mosfet to switch on. The power supply is realized by a capacitive power supply.
The problem is following: When I give a high signal (5V) to the Mosfet and it turns on the way it should. But if the signal is low (0V) the mosfet does not turn off. Instead the lamp is shining less bright. Even if put out the cable from the µC to the mosfet and hold it to the source/ground the light doesn't turn off.
When I put the grounds of the mosfet (at source and the ground at the 1k resistor) to a separate "ground 2" the mosfet shows the same behaviour BUT now I can remove the signal from the µC and the lamp is totally off.
The mosfet is working properly by the way. When test it all alone with a different ground it is working.
I think it has something to do with the grounds but when I measure the signal based on the ground with a differential probe on the oscilloscope, then there is the right signal at the mosfet.
My question is: Why does the mosfet behave like this and how can I make it work properly?
Sorry for my grammar, I am from germany
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