Unusual functions of cheap parts
 

In article ,
Paul Keinanen wrote:

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).

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 ;-)

Unusual functions of cheap parts
 

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.

Unusual functions of cheap parts
 

On Fri, 25 Nov 2005 20:48:19 GMT, Al wrote:

In article ,
Paul Keinanen wrote:

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).

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.

Unusual functions of cheap parts
 

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

Unusual functions of cheap parts
 

A simple 1.0 K Ohm or so carbon film resistor placed across the
line makes a very nice display after a couple of seconds. They also
make a handy fuse to trigger a little firecracker when used as a
"surprise" for some unsuspecting technician placed across his load
behind the workbench when he turns it on in the morning.

boB
K7IQ

Unusual functions of cheap parts
 

In article ,
Al wrote:

In article ,
Paul Keinanen wrote:

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).

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.

Unusual functions of cheap parts
 

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"

Unusual functions of cheap parts
 

On Fri, 25 Nov 2005 12:29:52 -0800, Roy Lewallen
wrote:

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?

Certainly.

I used arc welding glasses when conducing these experiments.

Some trivia:

In the silent film era, actors had eye problems due to the UV
radiation from arc studio lamps.

Most of the usable illumination from the arc lights is actually from
the glowing carbon electrodes.

"Automatic arc lights" used a solenoid in series with the arc to keep
the distance constant between the poles regardless of carbon electrode
burnout. I assume that if this is to be used with a AC arc light, both
the moving coil as well as the static coil should carry the arc
current.

Paul OH3LWR

Unusual functions of cheap parts
 

Frithiof Andreas Jensen wrote:

"Henry Kiefer" skrev i en meddelelse
...


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.


E.G the CMOS 4007. See the old handbooks for a '100dB
amplifier' based on a RCA chip - there was a wiring
error in that old description - IIRC it was 3800? -
whatever, the 4007 is the same chip.

Murray vk4aok

Unusual functions of cheap parts
 

On Sat, 26 Nov 2005 21:19:18 +1000, Murray wrote:

Frithiof Andreas Jensen wrote:

E.G the CMOS 4007. See the old handbooks for a '100dB
amplifier' based on a RCA chip - there was a wiring
error in that old description - IIRC it was 3800? -
whatever, the 4007 is the same chip.

The Motorola McMOS handbook (2nd edition 1974) warns about this usage
by pointing out that by cascading three such AC coupled stages, the
last stage will be saturated by the noise from the first stage.

Paul OH3LWR

Unusual functions of cheap parts
 

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


Take one P channel Jfet and one N channel Jfet and connect them
in series so the two sources are together, connect the gate of
each transistor to the other one's drain. This is known as a lambda
connection, and if you plot the voltage vs current from drain to drain
you will see a negative resistance region, usually around 3v
(depending on the transistors). The circuit will work as a tunnel
diode oscillator up to 100-200mhz.

Unusual functions of cheap parts
 

Unusual functions of cheap parts
 

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.

Unusual functions of cheap parts
 

"Si Ballenger" wrote in message
...
On Fri, 25 Nov 2005 20:48:19 GMT, Al wrote:

In article ,
Paul Keinanen wrote:

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).

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.

Exactly-when I was a kid we made them like this all the time. As I
recall, it came from "700 scientific experiments, with
illustrations"...

Unusual functions of cheap parts
 

On Fri, 25 Nov 2005 22:13:38 -0500, Phil Hobbs
wrote:

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

I've used a light bulb in series with a rectifier to charge a car
battery (just make sure that line ground goes to chassis ground ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

Unusual functions of cheap parts
 

John Devereux wrote in
:

ehsjr 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).

To save power, use the LEDs of a backlight to measure the ambient light
to decide to switch the backlight on or not.

M.
--
Bitte auf antworten.

Unusual functions of cheap parts
 

On Sat, 26 Nov 2005 11:56:55 +0200, Paul Keinanen
wrote:

On Fri, 25 Nov 2005 12:29:52 -0800, Roy Lewallen
wrote:

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?

Certainly.

I used arc welding glasses when conducing these experiments.

Some trivia:

In the silent film era, actors had eye problems due to the UV
radiation from arc studio lamps.

Most of the usable illumination from the arc lights is actually from
the glowing carbon electrodes.

"Automatic arc lights" used a solenoid in series with the arc to keep
the distance constant between the poles regardless of carbon electrode
burnout. I assume that if this is to be used with a AC arc light, both
the moving coil as well as the static coil should carry the arc
current.

Paul OH3LWR

We worked with a company that was developing an xray imager, and was
buying very expensive electrically conductive glass (gigohms per
square sort of range.) They discovered that certain welding glass was
identical and about 1/20 the price.

John

Unusual functions of cheap parts
 

1n914/4148 as silicon temperature sensor. (forward bias)

I used a 1n4007 as a temperature sensor to repair a water bed
heater.

What is the rest of the circuit you used?

--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

Unusual functions of cheap parts
 

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

Unusual functions of cheap parts
 

Jim Thompson wrote:
On Fri, 25 Nov 2005 22:13:38 -0500, Phil Hobbs
wrote:


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


I've used a light bulb in series with a rectifier to charge a car
battery (just make sure that line ground goes to chassis ground ;-)

...Jim Thompson


Going the other direction, I used the elements from a toaster as a load to
discharge wet-cell lead-acid batteries. It was a discharge/charge cycling test.

John

Unusual functions of cheap parts
 

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 Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

Unusual functions of cheap parts
 

A metal case of a crystal should never soldered!! This may break the
oscillation characteristics. At least you must know what you're doing here.
This type of built-in failure mode is often seen in products.
Otherwise it is interesting!

Another error with crystals is to ultrasonic the populated pcb. With the
right sonic frequency the crystals comes in resonance - cracking of parts or
wires!

- Henry


"RST Engineering" schrieb im Newsbeitrag
...
Take a crystal for which you need a constant temperature. Solder the
cathode of a cheap diode (1N4148 etc.) to the crystal case. Solder one
end
of a moderately low value half-watt resistor to the case. Bring out the
anode of the diode, the free end of the resistor, and the crystal case on
wire leads and encapsulate the crystal-diode-resistor in heat shrink. Use
the diode as your temperature sensor, the resistor as your heating
element,
an opamp/driver transistor as the comparator/amplifier and bingo, the
world's cheapest crystal oven. Bang-bang or linear, your choice.

Jim



eh Henry Kiefer wrote:
Hi all -


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

Best regards -
Henry

Unusual functions of cheap parts
 

As a youngster I played with TTL DIP-ICs in my chamber and my parents next
room felt that the tv was going crazy. The pins had long wires...

- Henry

schrieb im Newsbeitrag
oups.com...
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.

Unusual functions of cheap parts
 

The 4007 is the classic crystal oscillator circuit.
Don't forget the temperature characteristics!

- Henry

"Murray" schrieb im Newsbeitrag
...
Frithiof Andreas Jensen wrote:

"Henry Kiefer" skrev i en meddelelse
...


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.


E.G the CMOS 4007. See the old handbooks for a '100dB
amplifier' based on a RCA chip - there was a wiring
error in that old description - IIRC it was 3800? -
whatever, the 4007 is the same chip.

Murray vk4aok

Unusual functions of cheap parts
 

That is not new to me but thanks!
Is the oscillator useful at 150MegHz? Modulable? Maybe I can make
transmitter...
Tell us more, please.

cu -
Henry


"wa2mze(spamless)" schrieb im Newsbeitrag
. ..
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


Take one P channel Jfet and one N channel Jfet and connect them
in series so the two sources are together, connect the gate of
each transistor to the other one's drain. This is known as a lambda
connection, and if you plot the voltage vs current from drain to drain
you will see a negative resistance region, usually around 3v
(depending on the transistors). The circuit will work as a tunnel
diode oscillator up to 100-200mhz.

Unusual functions of cheap parts
 

Don't forget the LED as an low-noise zener diode with integrated function
control. Some high-fidelity enthusiasts use this in good audio amplifiers.

- Henry

"ehsjr" schrieb im Newsbeitrag
news:R3thf.9922$BU2.983@trndny01...
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



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

Unusual functions of cheap parts
 

There even exists LED specially taylored to the needs of doing duplex
operation.

- Henry


"Frithiof Andreas Jensen"
schrieb im Newsbeitrag ...

"Henry Kiefer" wrote in message
...

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.

Unusual functions of cheap parts
 

Bob Pease of National Semi mentioned a ONE AND ONLY transistor circuit
above/under voltage rail converter (with detailed theory). I cannot remember
the details. But interesting if sometime a slightly voltage behind the power
rail is needed. For example to power a CMOS Opamp now doing rail-input.

- Henry

Unusual functions of cheap parts
 

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
wrote:


"Henry Kiefer" wrote in message
...

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

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


And optocouplers can do interesting things:

Very simple high-voltage opamp, up to 400 volts p-p.

Isolated totem-pole driver, from a few volts up to 400.

Current limiter.

Low-leakage diode, sort of like an LED painted black.

John

Unusual functions of cheap parts
 

In article ,
Henry Kiefer wrote:
Don't forget the LED as an low-noise zener diode with integrated function
control. Some high-fidelity enthusiasts use this in good audio amplifiers.

It also works for this:
Vcc
!/c
--/\/\/\---+------!
! !\e
V !
--- ----/\/\/--+--- too load
! !
--------------------

You get a current limit and an indicator light.


--
--
forging knowledge

Unusual functions of cheap parts
 

Can you give details?

- Henry


"John Larkin" schrieb im
Newsbeitrag ...
On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
wrote:


"Henry Kiefer" wrote in message
...

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

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


And optocouplers can do interesting things:

Very simple high-voltage opamp, up to 400 volts p-p.

Isolated totem-pole driver, from a few volts up to 400.

Current limiter.

Low-leakage diode, sort of like an LED painted black.

John

Unusual functions of cheap parts
 

On Sun, 27 Nov 2005 00:54:27 +0100, "Henry Kiefer"
wrote:

Can you give details?

- Henry


"John Larkin" schrieb im
Newsbeitrag ...
On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
wrote:


"Henry Kiefer" wrote in message
...

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

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


And optocouplers can do interesting things:

Very simple high-voltage opamp, up to 400 volts p-p.

Isolated totem-pole driver, from a few volts up to 400.

Current limiter.

Low-leakage diode, sort of like an LED painted black.

John



I posted some opamp schematics to abse a while back. I guess I could
do it again if they're no longer available.

The others chould be fairly obvious.

John

Unusual functions of cheap parts
 

On Sat, 26 Nov 2005 15:41:27 -0800, John Larkin
wrote:

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
wrote:


"Henry Kiefer" wrote in message
...

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

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


And optocouplers can do interesting things:

Very simple high-voltage opamp, up to 400 volts p-p.

Isolated totem-pole driver, from a few volts up to 400.

Current limiter.

Low-leakage diode, sort of like an LED painted black.

John

A latch.

--

Boris Mohar

Unusual functions of cheap parts
 

Am 25 Nov 2005 06:28:21 -0800 schrieb :

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.

At least the audio amp, this is nice to build with some Inverters (4069)
with resistive Feedback.


--
Martin

Unusual functions of cheap parts
 

Am Fri, 25 Nov 2005 22:13:38 -0500 schrieb 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.

An electric arc with just 3V from two D-cells? I thought the arc needs at
lesat 20V burning voltage.

--
Martin

Unusual functions of cheap parts
 

Martin wrote:
Am Fri, 25 Nov 2005 22:13:38 -0500 schrieb 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.

An electric arc with just 3V from two D-cells? I thought the arc needs
at lesat 20V burning voltage.


It ran off 120 V. Parse the sentence as "two D-cell-carbon arc lamp." An
earlier poster talked about building AC-powered arc lamps using the carbon
rods from dry cells.

Cheers,

Phil Hobbs

Unusual functions of cheap parts
 

On Sat, 26 Nov 2005 21:40:53 -0500, Boris Mohar
wrote:

On Sat, 26 Nov 2005 15:41:27 -0800, John Larkin
wrote:

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
wrote:


"Henry Kiefer" wrote in message
r-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.


And optocouplers can do interesting things:

Very simple high-voltage opamp, up to 400 volts p-p.

Isolated totem-pole driver, from a few volts up to 400.

Current limiter.

Low-leakage diode, sort of like an LED painted black.

John

A latch.


Right, if CTR 1.

John

Unusual functions of cheap parts
 

Am Sat, 26 Nov 2005 16:16:27 +0000 (UTC) schrieb Matthias Weingart
:

John Devereux wrote in
:

ehsjr 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).

To save power, use the LEDs of a backlight to measure the ambient light
to decide to switch the backlight on or not.

But how to decide to switch it off? I think there you have to sample -
switch of for a short time and test. This could give a flickering
backlight.

--
Martin

Unusual functions of cheap parts
 

In article ,
Henry Kiefer wrote:
Bob Pease of National Semi mentioned a ONE AND ONLY transistor circuit
above/under voltage rail converter (with detailed theory). I cannot remember
the details. But interesting if sometime a slightly voltage behind the power
rail is needed. For example to power a CMOS Opamp now doing rail-input.

For a good discussion of Bob Pease's "April Fool" negative voltage
generator, see:

http://www.edaboard.com/viewtopic.php?p=423522

Unfortunately you have to log in to the site to see the drawings & photos.

I don't think it produces nearly enough current to power an opamp.

Unusual functions of cheap parts
 

When I was a teenager and my brothers started bothering me with their loud
TV, I took a 220V relay, put one of the coil leads through its normally
closed contact group, and plugged the relay into the mains behind the wall
where the TV was. Made an exelent TVI/RFI generator, I thought the TV is
going to blow up.


"Henry Kiefer" wrote in message
...
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