monostable multivibrator problem

crutschow said:

A BJT with a voltage rating of at least 150V, for example a 2N5550. The design of the circuit depends upon the capacitance of the load.

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how to connect the bjt which point goes to the output of 555, which one is the output and which one goes to the transformer?

The transformer and variac generate 100VDC from the mains using a diode bridge and filter capacitor. The output of the 555 drives the transistor base through a resistor. This 100V goes through another resistor to the transistor collector with the emitter going to ground. That's what generate the desired pulse at the transistor collector. To determine the resistor values requires the value of the load capacitance.

Common Base Bjt , Sir . And links to each part by r-series .

Load may be the motor and how ... ?

crutschow said:

The transformer and variac generate 100VDC from the mains using a diode bridge and filter capacitor. The output of the 555 drives the transistor base through a resistor. This 100V goes through another resistor to the transistor collector with the emitter going to ground. That's what generate the desired pulse at the transistor collector. To determine the resistor values requires the value of the load capacitance.

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so this is my simulation after I replace the plate and the distance with a normal capacitor....



and C1 = 0.20905 pF
C2 = 0.21942 pF
C3 =12.48558 pF

so with this load capacitance what is the value of the resistor? is there any calculation for choosing the resistor?

by the way, I tried to search 2n5550, but apparently it's already discontinued in here. Is there any subtitution for that transistor?

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phongphanp said:

Load may be the motor and how ... ?

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The load is not a motor... but two plates separate 1 m apart like shown below



So finally after struggling I got the most close that I ever got this is the circuits



and this is the signal



But I can't got any faster than that. I think it's because the trigger is not fast enough to go all the way down.

So my problem right now is how to increase it to 100V at least. Any suggestion guys regarding the resistor value