Re: [TCML] Dan Mccauley, et al staccato PCB SC2026

[futuret@xxxxxxx]

Hi Jim,

Yes, it's floating, and yes I used it with (4) 833A tubes.  I don't
remember the resistor getting hot, but maybe I never checked
for that?   I drove the SCR directly from the 555 timer (through
the resistor).  Actually I probably never ran that coil for longer than
30 seconds at a time or so, due to its ferocious power.  I ran it
longer using staccato, and a few times while videotaping it.

Cheers,
John


-----Original Message-----
From: Jim Mora <wavetuner@xxxxxxxxx>
To: 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx>
Sent: Fri, Jun 26, 2009 12:21 am
Subject: RE: [TCML] Dan Mccauley, et al staccato PCB SC2026



Hi John,

The 50RIA120 is still available from Avnet. This iteration is 
manufactured
by Visnay and is RoHS compliant. It can handle 50-80amps and much more 
peak.
The peak off voltage is 1200 though. I guess this is ok because it is
floating? The relative gate voltage is about 1 volt with a 200-400ma 
latch
current. I will have to review the 555 specs to see if it can provide 
this
current without additional circuit assistance. I am told the 100ohm 
trigger
limit resistor gets hot even with a 1 or 2 883x coil.

Have you ever used this SCR with a (4)833x's? General suggestions 
welcome.

Thanks,
Jim Mora


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On 
Behalf
Of futuret@xxxxxxx
Sent: Thursday, June 25, 2009 5:44 PM
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] Dan Mccauley, et al staccato PCB SC2026

Hi Jim,

Apparently the SCR never sees the full plate voltage.  This
permits it to survive despite a 1200V or lower max voltage
rating.  SCR's are said to be more robust in general than
triacs.  Triacs don't offer any advantage.  I haven't had
any problem with turning off the SCR's.  They turn off
during the negative 60Hz half cycle.  I had problems with
triacs blowing out, but no problems with SCR's.  Of course
my SCR's had a much higher voltage and current rating,
so that's part of the reason.  I used an IR50RIA120 SCR,
but it was overkill actually.  This work was done a number
of years ago, so others may have more information/findings
at this time.

Cheers,
John


-----Original Message-----
From: Jim Mora <wavetuner@xxxxxxxxx>
To: 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx>
Sent: Thu, Jun 25, 2009 5:53 pm
Subject: [TCML] Dan Mccauley, et al staccato PCB SC2026



Hi All,

I am going to put together the group buy printed and silk screened PCB
and
staccato electronics circa 3-6-03 before I loose all the stuff. This
will be
to pulse a 4x 833C tube coil. It has been boxed since 2003 - parts from
DigiKey. Is there any mods, chages, or enhancements I should know about?

What would be a hearty SCR or triac selection for this application?
Will I
need an additional special driver for the gate? A suggested SCR or Triac
that will do this comfortably would be much appreciated! It would be
seeing
up to 4-5kv @ ~ 2.2amps to ground (all filaments/cathodes are common. I
have
heard problems of turning off the SCR once gated which is how they were
intended as I recall. Would a triac be a better choice?

Thanks, Jim Mora
________________________________________
"I do not think that the wireless waves I have discovered will have any
practical application"
Heinrich Hertz

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