Unusual functions of cheap parts

[Ban]

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

 

[Frithiof Andreas Jensen]

"Henry Kiefer" <otc_friend@gmx.net> wrote in message
news:4385b3b1$1$27887$9b4e6d93@newsread4.arcor-online.net...

Do you know of other interesting devices or circuits good for misuse?

LED's work both ways, as a light emitter and a photodiode.

The inbuilt colour filter can be used to distinguish between Grass and Not
grass f.ex. by comparing output from a red and a green LED using white light
as illumination.

Back when fiber was ex$$$pensive one often saw clever circuitry using two
transmitters to form a duplex connection over a single fiber.

The USD 10 solar powered garden lamps will, with a little persuation, yield
a nice solar cell well below the price of a similar unit in the shops -
and - two 600 mAh NiMh batteries and a grotty circuit for switching the LED.

 

[John Devereux]

ehsjr <ehsjr@bellatlantic.net> writes:

Henry Kiefer wrote:
Do you know of other interesting devices or circuits good for misuse?
Best regards -
Henry

An LED as a shunt regulator. Also, as a varicap.
Ed

Also a photodetector that is insensitive to long wavelengths (because
of the high bandgap).


--

John Devereux

 

[Jorgen Lund-Nielsen]

John Larkin wrote:

On Thu, 24 Nov 2005 18:30:06 +0100, Jorgen Lund-Nielsen
jorgen.lund-nielsen@xxxxxxxxxxxxdesy.de> wrote:


Henry Kiefer wrote:

Hi all -

After my first thread going from "standard" cheap parts for up to vhf
frequency to a discussion about the usefulness of Spice simulator...... I
try it another time hopefully get attention of frustrated co-readers:

For example the rechtifier diode 1N4007 can be used as a rf switching diode,
for example as rx/tx-switch. This is because it is a pin structure diode.
This type is cheap and you can get it almost everywhere. It shows good
performance for the price. Surely for high-end you should do it with another
type tuned to the application it is made for. But anyway it works in some
circuits.

Do you know of other interesting devices or circuits good for misuse?

Best regards -
Henry

Tuner Switching Diodes like the european BA244 (NOT PIN-Diodes!) work
well as medium fast Step Recovery Diodes.



Tell me about it. I tried some pins to see if they would snap, and
they turn out to have incredibly mushy reverse recovery, Slop Recovery
Diodes.

I'll have to try the varicaps.

John

Hello John,

I wrote: NOT PIN - Diodes - as they wouldn't snap.

i mean Band Switching diodes for TV-Tuners like the BA244 and the BA682.

BA682 Datasheet:

http://www.vishay.com/docs/85530/85530.pdf

- and they snap! Try it!

Jorgen
dj0ud

 

[Jorgen Lund-Nielsen]

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

 

As an addition to the various mentions of common diodes as varactors
there is a well publicized British design for a frequency tripler that
will put out 2 watts at 1.3 GHz and uses five 1N914's in parallel.

I once built an HF transceiver that used CMOS logic chips for all
functions except an audio low noise amp and a voltage regulator...with
further thought those two could likely be done with CMOS logic too.

 

[RST Engineering]

And by varying the reverse bias through a current source (or moderately
large fixed resistor) you can make them into nifty phase shifters.

Jim

I wrote: NOT PIN - Diodes - as they wouldn't snap.

i mean Band Switching diodes for TV-Tuners like the BA244 and the BA682.

BA682 Datasheet:

http://www.vishay.com/docs/85530/85530.pdf

- and they snap! Try it!

Jorgen
dj0ud

 

[Frithiof Andreas Jensen]

"Henry Kiefer" <otc_friend@gmx.net> skrev i en meddelelse
news:4385b3b1$1$27887$9b4e6d93@newsread4.arcor-online.net...

Do you know of other interesting devices or circuits good for misuse?

Unbuffered logic gates can make a really bad but still useful analogue
amplifier by adding feedback and bias.

 

[John Larkin]

On Fri, 25 Nov 2005 12:46:17 +0100, Jorgen Lund-Nielsen
<jorgen.lund-nielsen@xxxxxxxxxxxxdesy.de> wrote:

John Larkin wrote:
On Thu, 24 Nov 2005 18:30:06 +0100, Jorgen Lund-Nielsen
jorgen.lund-nielsen@xxxxxxxxxxxxdesy.de> wrote:


Henry Kiefer wrote:

Hi all -

After my first thread going from "standard" cheap parts for up to vhf
frequency to a discussion about the usefulness of Spice simulator...... I
try it another time hopefully get attention of frustrated co-readers:

For example the rechtifier diode 1N4007 can be used as a rf switching diode,
for example as rx/tx-switch. This is because it is a pin structure diode.
This type is cheap and you can get it almost everywhere. It shows good
performance for the price. Surely for high-end you should do it with another
type tuned to the application it is made for. But anyway it works in some
circuits.

Do you know of other interesting devices or circuits good for misuse?

Best regards -
Henry

Tuner Switching Diodes like the european BA244 (NOT PIN-Diodes!) work
well as medium fast Step Recovery Diodes.



Tell me about it. I tried some pins to see if they would snap, and
they turn out to have incredibly mushy reverse recovery, Slop Recovery
Diodes.

I'll have to try the varicaps.

John

Hello John,

I wrote: NOT PIN - Diodes - as they wouldn't snap.

I got that!

i mean Band Switching diodes for TV-Tuners like the BA244 and the BA682.

BA682 Datasheet:

http://www.vishay.com/docs/85530/85530.pdf

- and they snap! Try it!

OK, I'll try some.


Thanks

John

 

[John Larkin]

On Fri, 25 Nov 2005 09:07:38 +0000, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

TO-220 bipolar transistors make nice temperature sensors.

I like that trick. Esp the isolated tab type.

Graham

There's also an LM35 in a TO-220 package! Ideal way to monitor a
heatsink.

John

 

[Paul Keinanen]

On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger <jono_1@bellsouth.net>
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).

The problem is that the carbon rod conducts heat quite well, so after
a while, any wooden object will catch fire .

Tap the free ends of the rods together. Move them apart as necessary.

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

 

[Ron G]

Our newspaper had an article on that.
Also, for model rockets, burning up an ordinary resistor can be used as a
super-cheap ignitor.
Best---
Ron

John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:361co1pavjfi56f0kmrm8phrtb64g2kmvo@4ax.com...

On Thu, 24 Nov 2005 18:30:06 +0100, Jorgen Lund-Nielsen
jorgen.lund-nielsen@xxxxxxxxxxxxdesy.de> wrote:

Henry Kiefer wrote:
Hi all -

After my first thread going from "standard" cheap parts for up to vhf
frequency to a discussion about the usefulness of Spice simulator......
I
try it another time hopefully get attention of frustrated co-readers:

For example the rechtifier diode 1N4007 can be used as a rf switching
diode,
for example as rx/tx-switch. This is because it is a pin structure
diode.
This type is cheap and you can get it almost everywhere. It shows good
performance for the price. Surely for high-end you should do it with
another
type tuned to the application it is made for. But anyway it works in
some
circuits.

Do you know of other interesting devices or circuits good for misuse?

Best regards -
Henry

Tuner Switching Diodes like the european BA244 (NOT PIN-Diodes!) work
well as medium fast Step Recovery Diodes.

Jorgen


I know a guy who uses surface-mount resistors as explosive detonators.

John

 

John Larkin wrote:

A 1N4007 can also be used as a drift step-recovery diode and as a
plasma avalanche diode. Together, two can generate a kilovolt edge
with a 100 ps risetime.

GAASfets make good fast analog switches; they behave pretty much like
jfets.

Wide-open LDO regulators make nice resettable fuses.

Ferrite beads do all sorts of interesting stuff.

Power mosfets make good heaters, and TO-220 bipolar transistors make
nice temperature sensors.

LVDS line receivers are surprisingly good comparators, and *fast*


I could go on...

John

tell us more John

NT

 

[Roy Lewallen]

Paul Keinanen wrote:

. . .
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.

Aren't you in danger of damaging your eyes from the UV emitted from the arc?

Roy Lewallen, W7EL

 

[Al]

In article <clieo1lq869ialc6um02omsfdt266dvr2c@4ax.com>,
Paul Keinanen <keinanen@sci.fi> wrote:

On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger <jono_1@bellsouth.net
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).

The problem is that the carbon rod conducts heat quite well, so after
a while, any wooden object will catch fire .

Tap the free ends of the rods together. Move them apart as necessary.

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

I would put a 100 watt lamp in series thereby limiting the current. I
would shave the ends down to points so they heated up rapidly. I put
them into a hollowed out fire brick and made a cheap furnace. Of course
don't look at it; it's like looking at the sun.

PS: I was 16 at the time ;-)

 

[Robert Obermayer]

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.

 

[Si Ballenger]

On Fri, 25 Nov 2005 20:48:19 GMT, Al <no.spam@wanted.com> wrote:

In article <clieo1lq869ialc6um02omsfdt266dvr2c@4ax.com>,
Paul Keinanen <keinanen@sci.fi> wrote:

On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger <jono_1@bellsouth.net
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).

The problem is that the carbon rod conducts heat quite well, so after
a while, any wooden object will catch fire .

Tap the free ends of the rods together. Move them apart as necessary.

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


I would put a 100 watt lamp in series thereby limiting the current. I
would shave the ends down to points so they heated up rapidly. I put
them into a hollowed out fire brick and made a cheap furnace. Of course
don't look at it; it's like looking at the sun.

The current limiter I saw used a glass pie pan with pieces copper
metal on each side with salty water as the electrolyte. It would
start to steam some when in operation. The furnace was a small
clay flower pot with holes in each side with the carbon rods
sticking inside until they touched.

 

[Phil Hobbs]

Si Ballenger wrote:

I would put a 100 watt lamp in series thereby limiting the current. I
would shave the ends down to points so they heated up rapidly. I put
them into a hollowed out fire brick and made a cheap furnace. Of course
don't look at it; it's like looking at the sun.


The current limiter I saw used a glass pie pan with pieces copper
metal on each side with salty water as the electrolyte. It would
start to steam some when in operation. The furnace was a small
clay flower pot with holes in each side with the carbon rods
sticking inside until they touched.

As a boy, I used an electric teakettle as a ballast for a two-D-cell carbon
arc lamp--worked great.

Cheers,

Phil Hobbs

 

[Ralph Barone]

In article <no.spam-94A7B5.15482025112005@news.verizon.net>,
Al <no.spam@wanted.com> wrote:

In article <clieo1lq869ialc6um02omsfdt266dvr2c@4ax.com>,
Paul Keinanen <keinanen@sci.fi> wrote:

On Thu, 24 Nov 2005 18:49:24 -0500, Jon Yaeger <jono_1@bellsouth.net
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).

The problem is that the carbon rod conducts heat quite well, so after
a while, any wooden object will catch fire .

Tap the free ends of the rods together. Move them apart as necessary.

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


I would put a 100 watt lamp in series thereby limiting the current. I
would shave the ends down to points so they heated up rapidly. I put
them into a hollowed out fire brick and made a cheap furnace. Of course
don't look at it; it's like looking at the sun.

PS: I was 16 at the time ;-)

I used a 0.5 or 0.7 mm pencil lead gently torqued down across the
terminals of a regulated DC power supply. Set the current limit very
low, crank the voltage up all the way and increase the current limit
until the center of the lead starts glowing red. Due to the heatsinking
effect of the binding posts, the lead will always heat up the most in
the center, then the carbon will start to evaporate and the remaining
lead will gradually neck down in the center until it is glowing white
hot. As soon as the lead breaks in the middle, you convert from
incandescent to carbon arc lamp, which usually surprises everybody
watching. The arc is good for about 5 seconds until the voltage drop
across the arc exceeds the capability of the power supply.

 

[**THE-RFI-EMI-GUY**]

I have also seen thermistors used as a self regulating thermal element
for a crystal oven.

Joe Leikhim K4SAT
"The RFI-EMI-GUY"

"Follow The Money"



Pooh Bear wrote:

John Larkin wrote:



TO-220 bipolar transistors make nice temperature sensors.



I like that trick. Esp the isolated tab type.

Graham

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

"Follow The Money"