Selection of Potentiometer value

[Paresh Chauhan]

Can any one help to as to how to select the potentiometer of correct rating.

I have 22,3 V (max) of supply from solar panel which is connected to zener diode circuit with parallel resistor of 1 k ohm to zener diode (3.0V) and parallel to zener diode is another resistor of 820 ohm which is connected to the photo transistor (BPX38-3 OSO) with Vce = 50 V, Vbe= 7 V maximum values. Between the ground and the emmitter of the photo transistor i have to connect the potentiometer which control the sensitivity of my photo Transistor to supply voltage to the gate terminal of MOSFET with Vgs= 16 V and Vds = 100 V which is connected to the actuator which is to be controlled with the phototransistor.

 

[Nigel Goodwin]

Sorry, but the circuit makes no sense, and that's not how you use a potentiometer.

 

[audioguru]

The base of the phototransistor is grounded then it does nothing.
The 3.3V zener diode might be smoking because its current is too high.
The maximum gate voltage of the Mosfet will be only 2.7V where the Mosfet barely turns on) if the base if the phototransistor is disconnected from ground.

 

[Paresh Chauhan]

The base of the phototransistor is grounded then it does nothing.
The 3.3V zener diode might be smoking because its current is too high.
The maximum gate voltage of the Mosfet will be only 2.7V where the Mosfet barely turns on) if the base if the phototransistor is disconnected from ground.

the base of transistor is not grounded it mistake from my side

 

[Paresh Chauhan]

Sorry, but the circuit makes no sense, and that's not how you use a potentiometer.

to connect the potentiometer i took some reference from online only. why do you think the circuit wont work

 

[Nigel Goodwin]

to connect the potentiometer i took some reference from online only. why do you think the circuit wont work

It's just shorting the emitter to ground, not doing anything useful to the circuit at all.

But the whole drawing (I wouldn't call it a 'circuit') makes little sense, what is it even supposed to do?.