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