Re: Tesla Coil Tuner

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

On 20 May 2005, at 20:45, Tesla list wrote:

> Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi Paul,
>
> The modern CMOS version of the old 70's style 555 timer is really VERY
> different and very often NOT just a drop in replacement.  There were
> many warnings at the time, but they got forgotten...  The CMOS version
> has a number of new tricks and lost a few old ones.  The 50%
> oscillator circuit is a nice "new trick" ;-))  One should contrast and
> compare the data sheets to get the coolest version for a specific
> application.  They probably should have made a whole new part number,
> but the "sales guys made them do it"...  It is really funny to watch
> some guy plug the CMOS  version into a $30,000 power supply that uses
> it as the main oscillator and see the power supply cremate itself
> :o)))

And of course the old bipolar 555 used to crowbar its supply when it
switched. Awful design.

Malcolm

> The meter's inductance will probably be significant at say 200kHz.
> Thus, "fiddling around" with the resistances will be needed.  But that
> should be real easy stuff to fix.  Get the meter to go to full scale
> into a short for the full range of frequencies....  Just use a little
> potentiometer to "fix it" ;-)
>
> Cheers,
>
>          Terry
>
>
>
> At 06:15 PM 5/20/2005, you wrote:
> >Terry,
> >Good news. I got my TCT working and borrowed a frequency counter to
> >calibrate the pot scale. It puts out from 43 kHz to 640 kHz. Reading
> >directly across the output to ground, I get 3.2 vDC. The output
> >deflects my meter nicely. I left the bipolar diode in place and just
> >fed the output from the LED directly into the meter. I do need to do
> >some figuring and adjust the meter with the correct shunt and/or
> >resistor.
> >
> >Thanks a lot for all of your comments and advice. Despite my
> >misfires, this has turned out perfectly and I am very pleased.
> >
> >I do have to admit that it took me almost 10 hours to complete this
> >project. It is extremely difficult to solder between my vision and
> >shaky hands. It required a lot of trying and then retrying with
> >considerable cleanup of misplaced solder. I think it looks pretty
> >good as well. I wish my son hadn't broken my digital camera for me. I
> >would like to show some pics. Regards. Paul Think Positive
> >
>
>
>