Unusual functions of cheap parts

[John Larkin]

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
<frithiof.jensen@die_spammer_die.ericsson.com> wrote:

"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.

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

 

[Henry Kiefer]

forward biased!

- Henry

"Oliver Betz" <OBetz@despammed.com> schrieb im Newsbeitrag
news:438da5d3.276919038@z1.oliverbetz.de...

"Henry Kiefer" <otc_friend@gmx.net> wrote:

[...]

If you need a zener diode with very low noise you can use LEDs. That has
the

you mean forward biased? Reverse breakdown of most cheap LEDs is IIRC
around 100V.

Oliver
--
Oliver Betz, Muenchen (oliverbetz.de)

 

[Henry Kiefer]

Can you give details?

- Henry


"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> schrieb im
Newsbeitrag news:nasho1do5hpdjfa6iq5tjsqadruc4taqai@4ax.com...

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
frithiof.jensen@die_spammer_die.ericsson.com> wrote:


"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.


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

 

[John Larkin]

On Sun, 27 Nov 2005 00:54:27 +0100, "Henry Kiefer"
<otc_friend@gmx.net> wrote:

Can you give details?

- Henry


"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> schrieb im
Newsbeitrag news:nasho1do5hpdjfa6iq5tjsqadruc4taqai@4ax.com...
On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
frithiof.jensen@die_spammer_die.ericsson.com> wrote:


"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.


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

 

[Ken Smith]

In article <4388f068$1$27889$9b4e6d93@newsread4.arcor-online.net>,
Henry Kiefer <otc_friend@gmx.net> 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.


--
--
kensmith@rahul.net forging knowledge

 

[Boris Mohar]

On Sat, 26 Nov 2005 15:41:27 -0800, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
frithiof.jensen@die_spammer_die.ericsson.com> wrote:


"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.


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

 

[Martin]

Am 25 Nov 2005 06:28:21 -0800 schrieb <skavanagh72nospam@yahoo.ca>:

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

 

[Martin]

Am Fri, 25 Nov 2005 22:13:38 -0500 schrieb Phil Hobbs
<pcdhSpamMeSenseless@us.ibm.com>:

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

 

[Phil Hobbs]

Martin wrote:

Am Fri, 25 Nov 2005 22:13:38 -0500 schrieb Phil Hobbs
pcdhSpamMeSenseless@us.ibm.com>:

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

 

[John Larkin]

On Sat, 26 Nov 2005 21:40:53 -0500, Boris Mohar
<borism_-void-_@sympatico.ca> wrote:

On Sat, 26 Nov 2005 15:41:27 -0800, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen"
frithiof.jensen@die_spammer_die.ericsson.com> wrote:


"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.


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

 

[Martin]

Am Sat, 26 Nov 2005 16:16:27 +0000 (UTC) schrieb Matthias Weingart
<mwnews@pentax.boerde.de>:

John Devereux <jdREMOVE@THISdevereux.me.uk> wrote in
news:8764qh82fw.fsf@cordelia.devereux.me.uk:

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).

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

 

[David DiGiacomo]

In article <4388fc27$0$20854$9b4e6d93@newsread2.arcor-online.net>,
Henry Kiefer <otc_friend@gmx.net> 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.

 

[Matthias Weingart]

Martin <martin.lenz@gmx.at> wrote in
newsps0vsn10r8lri9x@news.gmx.at:

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.

Ok, you found the skeleton in the closet. You can not use
this method to switch it off - but it is not required in most cases.
Think of a cell phone - the backlight goes on every time you press a
key, and it is going off after 10 seconds.

M.
--
Bitte auf mwnews2@pentax.boerde.de antworten.

 

[Martin]

Am Sun, 27 Nov 2005 09:57:23 +0000 (UTC) schrieb Matthias Weingart
<mwnews@pentax.boerde.de>:

Martin <martin.lenz@gmx.at> wrote in
newsps0vsn10r8lri9x@news.gmx.at:

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.
Ok, you found the skeleton in the closet. You can not use
this method to switch it off - but it is not required in most cases.
Think of a cell phone - the backlight goes on every time you press a
key, and it is going off after 10 seconds.

OK, so you can decide to not switch it on and save some mAs.

--
Martin

 

[Fred Abse]

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

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

Known as "Klieg Eyes", (from "Klieg Lamp")

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)

 

[Fred Abse]

On Sat, 26 Nov 2005 10:16:23 -0500, wa2mze(spamless) wrote:

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.

Early marine transmitters did it that way.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)

 

Martin wrote:

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.

Most of the audio section was done that way. But the product detector
had low impedance output and the CMOS amp was too noisy at 50 ohms. A
transformer might have done the job but a common-base amp seemed more
practical and less prone to picking up hum.

Steve

 

[Martin]

Am Sat, 26 Nov 2005 22:35:18 -0500 schrieb Phil Hobbs
<pcdhSpamMeSenseless@us.ibm.com>:

Martin wrote:
Am Fri, 25 Nov 2005 22:13:38 -0500 schrieb Phil Hobbs
pcdhSpamMeSenseless@us.ibm.com>:

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.

OK I liked to do that myself, but not from our 230V mains power, but

with a transformer, 22V, and 30A short circuit.
--
Martin

 

[Winfried Salomon]

Hello Jim,

Jim Thompson wrote:
[...]

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.

[...]

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.

thank you, then I suppose the 2N3905 oder 2N2905 are fitting for a large
signal amplifier.

mfg. Winfried

 

[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.
--
Cheers!
Rich
------
"I don't drink water; fish fuck in it."
-- W.C. Fields