Author Topic: High voltage spike Generator  (Read 1827 times)

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Offline Monostable

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High voltage spike Generator
« on: April 18, 2016, 08:13:46 pm »
Hello everyone !

This weekend I got my hands on a toroidal transformer with unknown characteristic except that it was made to be used with 110v 400Hz.
It has a primary and two secondary (as drawn below)
Since I don't have an easy access to 110v 400Hz it was a bit useless to me, so I though why not try to generate some voltage spikes.
So I connected the primary in series with a mosfet (IRF540) to my DC power supply, set the voltage at 3V and a current limit at around 50mA.
I then connected the gate of the mosfet to function generator and made it output a square wave (0-5V@400Hz).

And sure enough when I touched the secondary I felt a little tingling.
I tried to measure it with a multimeter it just displayed 23V AC, so I tried hooked it to my analog scope with a x10 probe and sure enough It displayed a spike at 200V around the rising edge of the square wave.
So I increased a bit the current limit and the spike's voltage increased, I went to 600V and then decided to stop because I felt that I would blow up my scope's input.


I have several questions :
  • Is it safe for my DC power supply to that ?
  • How can I safely measure the voltage spike without damaging my oscilloscope
  • At which point does the voltage become dangerous for a human ?
 

Offline danadak

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Re: High voltage spike Generator
« Reply #1 on: April 18, 2016, 08:39:34 pm »
Is it safe for my DC power supply to that ?

No, unless you install diode or zener clamps on output.

How can I safely measure the voltage spike without damaging my oscilloscope

Create your own 100X probe with a V divider, but of equal concern is survivability of the MOSFET,
exceeding its ratings.

At which point does the voltage become dangerous for a human ?

https://en.wikipedia.org/wiki/Electric_shock

Regards, Dana.
Love Cypress PSOC, ATTiny, Bit Slice, OpAmps, Oscilloscopes, and Analog Gurus like Pease, Miller, Widlar, Dobkin, obsessed with being an engineer
 

Offline Monostable

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Re: High voltage spike Generator
« Reply #2 on: April 19, 2016, 12:00:50 am »
But wouldn't putting a free will diode reduce the voltage spike on the secondary that I am trying to create ?
But I don't think I'll be playing around with high voltage anymore, it scares me a bit.

Although I did some calculation and I am only drawing (3V/0.05A)w or 0.15w.
And if I'm outputting from the secondary 600V (peak) the system can only deliver (0.15w/600V) which is 250µA (assuming there are no losses in the conversion).
Although the TRMS value on the DMM was 23V so that would be 6mA.

Are my calculation correct to estimate the output capability ?
 

Offline T3sl4co1l

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Re: High voltage spike Generator
« Reply #3 on: April 19, 2016, 12:16:53 pm »
Is it safe for my DC power supply to that ?

No, unless you install diode or zener clamps on output.

Why no?

What good will a diode do?

Exercise: analyze the circuit and demonstrate that these are useless. :)

Quote
At which point does the voltage become dangerous for a human ?

https://en.wikipedia.org/wiki/Electric_shock

This doesn't say anything about pulses, though.

If the pulse is short, you might not feel it, but it can still cause problems.  Best not to touch it in the first place...

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 


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