Low-voltage diac?

N

Neil Preston

Guest
Is there available a DIAC with breakover voltage ratings in the 5-15V range?
Or an equivalent device?

All I've seen so far are in the 50-60v range.

I wish to make a sensitive triac trigger to detect certain fault conditions
on an AC signal, and I need the negative resistance characteristics typical
of a diac, but at much lower threshhold voltage. It must also be
bidirectional.

Thanks,
Neil
 
"Neil Preston" <npreston@nospamgeocities.com> wrote in message
news:3IKAd.7273$iC4.496@newssvr30.news.prodigy.com...
Is there available a DIAC with breakover voltage ratings in the 5-15V
range?
Or an equivalent device?

All I've seen so far are in the 50-60v range.

I wish to make a sensitive triac trigger to detect certain fault
conditions
on an AC signal, and I need the negative resistance characteristics
typical
of a diac, but at much lower threshhold voltage. It must also be
bidirectional.

Thanks,
Neil
Click to expand...
Some DIACs are rated for 30V, but that's not as low as what you asked
for.

Maybe you should use a more complicated circuit like a PUT.
 
"Neil Preston" <npreston@nospamgeocities.com> wrote in
news:3IKAd.7273$iC4.496@newssvr30.news.prodigy.com:

Is there available a DIAC with breakover voltage ratings in the 5-15V
range? Or an equivalent device?

All I've seen so far are in the 50-60v range.

I wish to make a sensitive triac trigger to detect certain fault
conditions on an AC signal, and I need the negative resistance
characteristics typical of a diac, but at much lower threshhold
voltage. It must also be bidirectional.

Thanks,
Neil
Click to expand...
How about an MBS4992 (Motorola) ?
M
 
Neil Preston schrieb:
Is there available a DIAC with breakover voltage ratings in the 5-15V range?
Or an equivalent device?

All I've seen so far are in the 50-60v range.

Maybe 2 zeners connected "back-to-back" could work; "breakover"-voltage
Click to expand...
would be [Uz + 0.7] V.

HTH

Reinhard
 
On Thu, 30 Dec 2004 17:06:20 +0100, Reinhard Zwirner
<reinhard_zwirner@web.de> wrote:

Neil Preston schrieb:

Is there available a DIAC with breakover voltage ratings in the 5-15V range?
Or an equivalent device?

All I've seen so far are in the 50-60v range.

Maybe 2 zeners connected "back-to-back" could work; "breakover"-voltage
would be [Uz + 0.7] V.
Click to expand...
The original message read "... and I need the negative resistance
characteristics ..." :)

Your solution will mimic a low voltage diac but won't provide the
negative resistance characteristics.

--
Kind regards,
Gerard Bok
 
Gerard Bok wrote:

But either way: it's not a diac. (Rememer, the nice tiny device
that fires reliably, even in the absence of a soldering iron :)
Click to expand...
What about two zeners and a triac? That could be a nice diac :)



Thomas
 
On Fri, 31 Dec 2004 14:20:52 +0100, Zak <jute@zak.invalid> wrote:

Gerard Bok wrote:

But either way: it's not a diac. (Rememer, the nice tiny device
that fires reliably, even in the absence of a soldering iron :)

What about two zeners and a triac? That could be a nice diac :)
Click to expand...
Could well be. Provided that you get the triac fired on 12..15
volts.
--
Kind regards,
Gerard Bok
 
Gerard Bok schrieb:
On Thu, 30 Dec 2004 17:06:20 +0100, Reinhard Zwirner
reinhard_zwirner@web.de> wrote:

Neil Preston schrieb:

Is there available a DIAC with breakover voltage ratings in the 5-15V range?
Or an equivalent device?

All I've seen so far are in the 50-60v range.

Maybe 2 zeners connected "back-to-back" could work; "breakover"-voltage
would be [Uz + 0.7] V.

The original message read "... and I need the negative resistance
characteristics ..." :)

Your solution will mimic a low voltage diac but won't provide the
negative resistance characteristics.
Click to expand...
You're right; I've just read the first part of Neil's message <sigh>.
On the other hand I successfully built a low voltage dimmer with such
a "diac" a few years ago.

Greetinx

Reinhard
 
UJT inside a bridge?

Ah, what the heck. Use a PIC.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/
 
In article <41d55b9a.5603801@News.Individual.NET>,
Gerard Bok <bok118@zonnet.nl> wrote:
On Fri, 31 Dec 2004 14:20:52 +0100, Zak <jute@zak.invalid> wrote:

Gerard Bok wrote:

But either way: it's not a diac. (Rememer, the nice tiny device
that fires reliably, even in the absence of a soldering iron :)

What about two zeners and a triac? That could be a nice diac :)

Could well be. Provided that you get the triac fired on 12..15
volts.
Click to expand...
Sure, they usually have a max gate voltage of a volt or two. It looks
like a anti-parallel pair of diodes from gate to "cathode".

But, you'd have to use an SCR and a zener inside of a full wave bridge
because triacs are too slow and don't come unstuck at frequencies that
are too high. (Over a couple of hundred Hz, as I understand it).

Mark Zenier mzenier@eskimo.com Washington State resident
 
The MBS4992 looks like it would be perfect for my app. Unfortunately, it
appears to be no longer manufactured. Any suggestions for sources? (10-15
pcs.)


Neil

"Mike Diack" <moby@kcbbs.gen.middleearth> wrote in message
news:Xns95CFDD8011E90mobykcbbsgennz@203.96.92.12...
"Neil Preston" <npreston@nospamgeocities.com> wrote in
news:3IKAd.7273$iC4.496@newssvr30.news.prodigy.com:

Is there available a DIAC with breakover voltage ratings in the 5-15V
range? Or an equivalent device?

All I've seen so far are in the 50-60v range.

I wish to make a sensitive triac trigger to detect certain fault
conditions on an AC signal, and I need the negative resistance
characteristics typical of a diac, but at much lower threshhold
voltage. It must also be bidirectional.

Thanks,
Neil



How about an MBS4992 (Motorola) ?
M
Click to expand...
 
A bit of quick googling shows that the brokers (touts and shysters) are
sitting on mountains of them, but the regular supply lines are indeed
dry. I'm sort of amazed that these useful little widgets have gone on
the endangered species list. On semi still list them and Crown Audio are
still using them (in their CE series pro amps) so they gotta be out
there. Otherwise you could get creative with a bridge wrapped around a
little SCR (5060) and a couple of resistors. <sigh>
M


"Neil Preston" <npreston@nospamgeocities.com> wrote in
news:%BVCd.7280$F67.6246@newssvr12.news.prodigy.com:

The MBS4992 looks like it would be perfect for my app. Unfortunately,
it appears to be no longer manufactured. Any suggestions for sources?
(10-15 pcs.)


Neil

"Mike Diack" <moby@kcbbs.gen.middleearth> wrote in message
news:Xns95CFDD8011E90mobykcbbsgennz@203.96.92.12...
"Neil Preston" <npreston@nospamgeocities.com> wrote in
news:3IKAd.7273$iC4.496@newssvr30.news.prodigy.com:

Is there available a DIAC with breakover voltage ratings in the
5-15V range? Or an equivalent device?

All I've seen so far are in the 50-60v range.

I wish to make a sensitive triac trigger to detect certain fault
conditions on an AC signal, and I need the negative resistance
characteristics typical of a diac, but at much lower threshhold
voltage. It must also be bidirectional.

Thanks,
Neil



How about an MBS4992 (Motorola) ?
M
Click to expand...
 
Neil Preston wrote...
The MBS4992 looks like it would be perfect for my app. Unfortunately,
it appears to be no longer manufactured. Any suggestions for sources?
(10-15 pcs.)
Click to expand...
The MBS4992 was Motorola's version of GE's original 2n4992 SBS,
or Silicon-Bilateral Switch, which was widely second sourced.
Lot's of surplus places carry them, such as ampslab.com,
http://www.ampslab.com/trans_2n4992.htm


--
Thanks,
- Win
 
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