30V pulse from transistor-inductor circuit

Thread Starter

kyle7119

Joined Feb 11, 2011
84
I am trying to use to simulate this pulse:

TachOscillogram.jpg

I have designed the following circuit in LTSpice. However, I am struggling to get a larger voltage out of it. What can I add or adjust to get to 30V?

( I am measuring the voltage directly above L1 )

pulse.JPG

pulses.JPG
 

AlbertHall

Joined Jun 4, 2014
9,666
Put the inductor in series with the drain of the transistor, not the source.
What's the purpose of the diode?
It does nothing as shown.
Moving the inductor will be able to produce a large positive going spike, but the negative spike will still be limited to the supply voltage.
 

AlbertHall

Joined Jun 4, 2014
9,666
To get 30V positive and negative going spikes, start with a 30V peak-to-peak square wave and feed that through a capacitor to a resistor to ground. You will the desired spikes across the resistor with the width of the spikes being set by the RC time constant.
 

Alec_t

Joined Sep 17, 2013
11,164
.... and here's another option, which matches the oscillogram traces reasonably well for different rpms and load resistance.
Pulser.PNG
 

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Thread Starter

kyle7119

Joined Feb 11, 2011
84
For what purpose? If it's for automotive use, then the negative-going pulse portions are probably ignored/suppressed, so there's little point in generating those.
I built an engine monitor board for an experimental aircraft (using a Rotax 912 engine). I want to verify the tachometer "filter" circuit before I actually plug it into the aircraft. The circuit is supposed to limit the pulse to 5V. It works in steady state mode, but I want to verify it against high-voltage transients, both positive and negative.

D7 = BAT54S
D8 = PMEG4020ETP
D9 = PDZVTR4.3B

circuit.jpg

tach.JPG
 
Last edited:

eetech00

Joined Jun 8, 2013
1,869
Hmmm...Is this what your looking for?

PulserDriver_Mosfet_Test.png

The output shown is at 100Hz(6000RPM) but also works at 8.33Hz(500RPM). I'm thinking the clock generator could be made using a NE555 timer chip.

eT
 

Thread Starter

kyle7119

Joined Feb 11, 2011
84
Hmmm...Is this what your looking for?

The output shown is at 100Hz(6000RPM) but also works at 8.33Hz(500RPM). I'm thinking the clock generator could be made using a NE555 timer chip.

eT
Thanks for the circuit, it gave me some ideas.

Here is a circuit that does the same thing with a +/- 12V supply. However, I'm still trying to figure out how to do this (1) without the -12V supply and (2) without the bipolar square wave

working.JPG trace.JPG
 
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