Re: leader strike photo idea - Tesla coil spark current meter

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Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Peter,

Cool idea!!

I have burnt out LEDs doing this in the past but they "still 
light"!!  In fact, a "burnt out" LED lights fine under high 
voltage.  So it may seem like the LEDs work but if you go to power 
them up normally they might look dead.  However, if the LED still 
"works" who cares ;-))

I did look at the LM3914 circuit today but the LM3914 starts to pull 
off at 20kHz and is totally gone at 50kHz.  If one wants to do a 
linear bar graph, it would probably have to be made out of discrete 
comparators and such.  I might still look into that since it would be 
so cool ;-))

Cheers,

        Terry


At 08:30 AM 9/25/2006, you wrote:
> I have made a current meter covering a theoretical 6 orders of 
> magnitude using a simple resistor/LED chain.
> Circuit diagram here
> http://tesladownunder.com/HVpolarityVU1Schematic.jpg
> Pic here in action
> http://tesladownunder.com/HVpolarityVU1.jpg
> Also would you believe that a red LED could take such abuse and 
> still run with a 2 inch spark directly onto it (without reverse 
> protection).  Well for a few minutes at least on my ignition coil setup.
> http://tesladownunder.com/HVpolarityLEDSingle.jpg
>
> Peter
>
>
> > Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
> > Hi Jim,
> > I am working on an LM3914 bar graph "scope" to do this.  The only 
> > thing I don't know is how fast the LM3914 will operate.  It might 
> > have to go to near 1MHz!!
> > Cheers,
> >         Terry