Unusual functions of cheap parts

[Henry Kiefer]

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

 

[Stefan Heimers]

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

I never tried it myself, but I heard that some people abused opened memory
chips as cameras, back when CCD camera chips were too expensive for
hobbyists.

http://www.classiccmp.org/pipermail/cctalk/2004-May/042581.html

http://groups.google.com/group/comp...+chips+used+as+camera&rnum=6#f84b0f2d5c0b6da7

 

[Jorgen Lund-Nielsen]

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

 

[R.Freitag]

Henry Kiefer wrote:
[...]

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

Take away the hat of a 2N3055 and use it as a light sensor (sensitive).

Robert

 

[John Larkin]

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

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

 

[CA]

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

The LM317 as a radio transmitter

http://web.telia.com/~u85920178/tx/317-tx.htm

 

[John Larkin]

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

 

[Jim Thompson]

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. [snip]

Best regards -
Henry

That's an interesting use of the 1N4007. I've not tried that, what
kind of off capacitance do you get?

...Jim Thompson

 

[Boris Mohar]

Cadmium sulphide ( CdS ) LDR as a Beta radiation detector. Not sensitive to
Gamma radiation which can be an advantage because it will detect Beta in
presence of Gamma. You have to paint it black. Horrible temperature
sensitivity but you can use another CdS as reference.



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place

 

[John Larkin]

The LM317 as a radio transmitter

http://web.telia.com/~u85920178/tx/317-tx.htm

Cool. 3T regulators, 317 and LM1117 types, can be neat power amps, for
driving unipolar loads like motors and such. Sort of a follower with a
largish offset.

Hmmm, an LM1117 followed by a monster darlington becomes a
super-follower with roughly zero offset.

John

 

[John Larkin]

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

 

[Phil Hobbs]

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.

Okay, so I'm intrigued already. I have all the hardware available--two
1N4007s and a 3 kV adjustable power supply! How do I build one?

Cheers,

Phil Hobbs

 

[John Larkin]

Okay, so I'm intrigued already. I have all the hardware available--two
1N4007s and a 3 kV adjustable power supply! How do I build one?

Cheers,

Phil Hobbs

Google "Grekhov diode." A lot of the papers are for members only, but
this one gives the general idea:

http://www.ece.jhu.edu/~pps/ECE777/ADMAT/CircDev/Pulse-GENERATORS-SHAPERS/sub-nano-pulse1.pdf

Grekhov discovered both the DSRD and the plasma avalanche effects in
cheap power diodes. The core of the DSRD effect is that, if a PIN
diode is forward biased for not too many nanoseconds, the carriers
don't have time to float all around the place so the charge profile is
good for a nice reverse snap. HP did the same thing in their classic
1430 12-GHz sampling head, circa 1965 roughly.

This box used the DSRD effect, in a semiconductor that one would not
expect to be used in an application like this...

http://www.highlandtechnology.com/DSS/T220DS.html

We bias the snap diode +48 volts (yes, forward direction) for about 80
ns before we turn the drive around for the snap. It was originally
designed for use in a LEAP atom probe.

John

 

[Robert Obermayer]

Hi,

2N3055: one-time trigger diode with abt. 160v triggering voltage
[had some ones of unknown state left from a PSU that blew one of 5
transistors, replaced them with MJ15003]

various, sometimes expensive components: firecrackers, smoke bombs,
lamps (most of the time unintended )

old EPROMs: Lamp.Find some pins with low resistance and apply .5-2A.

the IC/transistor that was broken and took you some hours to find the
trouble:
Get 1-5 large caps (like 12 000µF 350V), charge them, and apply the
voltage to the part with a very large relay.
LOUD!

 

[Roy Lewallen]

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

 

[Jon Yaeger]

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.

Jon

 

[ehsjr]

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

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

 

[Bob Monsen]

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.

One of the MIT EE course videos on the web shows a demonstration of AC
across a pickle... it is an interesting effect. Not sure how the pickle
tastes afterward. Cooking hotdogs with AC is similar, but the pickle gives
off a much nicer translucent flickering glow. Very pretty.

---
Regards,
Bob Monsen

The question of the ultimate foundations and the ultimate meaning of
mathematics remains open; we do not know in what direction it will find its
final solution or even whether a final objective answer can be expected at
all. "Mathematizing" may well be a creative activity of man, like language
or music, of primary originality, whose historical decisions defy complete
objective rationalization.
- Hermann Weyl in 1944

 

[Pooh Bear]

TO-220 bipolar transistors make nice temperature sensors.

I like that trick. Esp the isolated tab type.

Graham

 

[Ban]

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.