You must have quite slow fuses in 110 V land if you can do a reliable
ignition without blowing the fuse. For 230 V operation, I would
suggest using a current limiting resistor (such as a large heater) or
an inductance (such as fluorescent light ballast) during the ignition.
When there is a solid arc, the current limiter can be shorted out.

Paul


Did you know that a carbon arc acts as a negative resistance? Run the
arc on DC and put an LC tuned circuit in series with the arc (coil of
heavy copper tubing) and you have a powerful oscillator.

On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger wrote:

Take apart a couple of D cell carbon-zinc batteries.

Wash off the carbon rods. Put each in a wooden clothes pin and connect the
attached ends to the mains voltage (US customers only, please).

Tap the free ends of the rods together. Move them apart as necessary. Very
bright! Much brighter than you are.

I put mine in series with Mom's iron, but the thermostat kept turning
it off.
--
Cheers!
Rich
------
"I don't drink water; fish **** in it."
-- W.C. Fields

Am Mon, 28 Nov 2005 22:14:17 GMT schrieb Rich the Newsgroup Wacko
:

On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger wrote:

Take apart a couple of D cell carbon-zinc batteries.

Wash off the carbon rods. Put each in a wooden clothes pin and connect
the
attached ends to the mains voltage (US customers only, please).

Tap the free ends of the rods together. Move them apart as necessary.
Very
bright! Much brighter than you are.

I put mine in series with Mom's iron, but the thermostat kept turning
it off.
One time I used an old Iron as a dummy-load for a 230V/1kW TRIAC power
control circuit (we had it in the lab for improvised BGA soldering). To
"satisfy" the thermostat I used a 30cm room fan.


--
Martin

hi,

sorry if you didnt like everything, but sometimes some voilence against
parts that cost you half a day of time and gave you a bad headache while
troubleshooting is necessary...

For more useful things, FETs actually can work as quite useful
one-component HF oscillators if wires and connection points are properly
chosen.With a second transistor one can build a working shortrange AM
transmitter.

A rather useful (works perfectly for SMPS uses) AC current probe for a
scope can be made by using a small UI cored RFI filter coil from a
monitor, connecting its windings in series and terminating with a 1ohm
resistor, to which a coax cable with BNC connector is soldered to.
The wire you want to measure the current in simply is fed trough the
core one time.
This only gives quantitative measurements unless calibrated but can be
very useful if you cant afford a real current probe.

The known resonant royer circiut used for CCFL inverters can be used for
larger inverters if appropriate parts are chosen, and can produce some
high frequency/high voltage with a transformer from a old TV (with no
internal rectifier).
This has its uses, besides connecting it to a old light bulb that works
as plasma globe or connecting both outputs to a large neon bulb
[Bienenkorbglimmlampe], which simply looks very nice but also produces
lots of RFI, so dont run it for too long.

FET gate drivers make nice TTL output stages for function generators, as
these can drive rather high currents and are fairly robust.

If a slowly, steadily changing linear voltage is necessary (for ex.
confirming the linearity of something) a 10turn precicion pot copuled
with a slow syncronous motor (a old microwave oven has a nice 2.5u/min
one) by some tape (so it slips/breaks when the pot is at its endpoint)
works nicely.

Zener diodes work fine as varicaps, at least at HF. The lower the zener
voltage and higher the power dissipation rating, the higher the C. As
someone else mentioned, transistor emitter-base junctions can be used as
either zeners (typical zener voltage around 5 volts) or varicaps.

A zener can be used as a broadband noise source. I've had the best luck
with zeners of 10 - 15 volt breakdown, with around 100 uA current. Some
are noisier than others, and they often have a critical current where
the noise is the greatest.

Tektronix used selected transistors to generate high voltage (~100
volts) fast steps (~100 ps rise time if I recall correctly) by
avalanching the collector. Some fraction of some common transistor types
worked satisfactorily in this application.

1N914 type diodes can be used as step recovery diodes to generate a step
with about a ns risetime -- maybe faster with a chip component and some
care. This could be the basis of a broadband harmonic generator.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Zener diodes work fine as varicaps, at least at HF. The lower the
zener voltage and higher the power dissipation rating, the higher the
C. As someone else mentioned, transistor emitter-base junctions can
be used as either zeners (typical zener voltage around 5 volts) or
varicaps.
A zener can be used as a broadband noise source. I've had the best
luck with zeners of 10 - 15 volt breakdown, with around 100 uA
current. Some are noisier than others, and they often have a critical
current where the noise is the greatest.

Tektronix used selected transistors to generate high voltage (~100
volts) fast steps (~100 ps rise time if I recall correctly) by
avalanching the collector. Some fraction of some common transistor
types worked satisfactorily in this application.

1N914 type diodes can be used as step recovery diodes to generate a
step with about a ns risetime -- maybe faster with a chip component
and some care. This could be the basis of a broadband harmonic
generator.
Roy Lewallen, W7EL

At a leading Ultrasonic flaw detector company we used simple low frequency
Motorola sot23 transistors in avalance mode for making a nice pulse
generator for 100MHz probes. These were better than the Zetex avalance
specified transistors.
--
ciao Ban
Apricale, Italy

Ban wrote:

Roy Lewallen wrote:

Zener diodes work fine as varicaps, at least at HF. The lower the
zener voltage and higher the power dissipation rating, the higher the
C. As someone else mentioned, transistor emitter-base junctions can
be used as either zeners (typical zener voltage around 5 volts) or
varicaps.
A zener can be used as a broadband noise source. I've had the best
luck with zeners of 10 - 15 volt breakdown, with around 100 uA
current. Some are noisier than others, and they often have a critical
current where the noise is the greatest.

Tektronix used selected transistors to generate high voltage (~100
volts) fast steps (~100 ps rise time if I recall correctly) by
avalanching the collector. Some fraction of some common transistor
types worked satisfactorily in this application.

1N914 type diodes can be used as step recovery diodes to generate a
step with about a ns risetime -- maybe faster with a chip component
and some care. This could be the basis of a broadband harmonic
generator.
Roy Lewallen, W7EL


At a leading Ultrasonic flaw detector company we used simple low frequency
Motorola sot23 transistors in avalance mode for making a nice pulse
generator for 100MHz probes. These were better than the Zetex avalance
specified transistors.

2N2369 for fast pulses.
2N2222 and even 2N2219 works, but a bit slower and they requiring more
voltage to avalance, but still 1nS rt
The Zetex are slower but can deliver much more current (up to 60A, ZTX
415 family).

Jorgen

Hello Jorgen,

Jorgen Lund-Nielsen wrote:

[.....]
2N2369 for fast pulses.

btw, do you know a standard complementary pnp-transistor for the 2N2369,
such like 2N3905 but with higher ft and less feedback capacitance? It
seems that the manufactorers have almost no data on their internet pages.

mfg. Winfried

On Sat, 26 Nov 2005 21:41:06 +0100, Winfried Salomon
wrote:

Hello Jorgen,

Jorgen Lund-Nielsen wrote:

[.....]
2N2369 for fast pulses.

btw, do you know a standard complementary pnp-transistor for the 2N2369,
such like 2N3905 but with higher ft and less feedback capacitance? It
seems that the manufactorers have almost no data on their internet pages.

mfg. Winfried

A 2N2369 is a gold-doped NPN, gold-doped to kill storage time and
improve recovery from saturation. I don't recall any PNP device with
gold-doping... or the equivalent.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Winfried Salomon wrote:
Hello Jorgen,

Jorgen Lund-Nielsen wrote:

[.....]

2N2369 for fast pulses.


btw, do you know a standard complementary pnp-transistor for the 2N2369,
such like 2N3905 but with higher ft and less feedback capacitance? It
seems that the manufactorers have almost no data on their internet pages.

mfg. Winfried

Maybe 2N4261 ? Have not looked into the datasheet, but as i remember,
i have seen them sometimes in complementary with the 2N2369

Jorgen