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'[EE]: My magical toy of wonderous mystery (transis'
2002\08\05@072438 by Kieren Johnstone

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Hi,
I thought I'd try an experiment based on a transistor; the transistor would switch an LED when two wires (one from +5V, other to base of transistor) were attached to a conductor of sorts.  It was cool, because you could hold one in one hand, the other in the other, and it would light up - two, even three people work holding hands :)  Anyway, I added another transistor, i.e. transistor 1 takes miniscule current, outputs small current, transistor 2 takes small current, outputs slightly larger etc. etc.
Anyway, I'm noticing weird results with 3 transistors.. the LED fluctuates in a dim state, even with the wires not touching.  Making *any sort* of contact with the wire connected to the primary transistor's base will light up the LED (quite brightly).  Don't even need to be near the +ve supply.  That's touching even the plastic insulation!
Anyway.. I don't know if this is called a transistor amp or what, but I was just wondering why it does this.. am I naturally generating current? :D

-Kieren

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2002\08\05@073714 by Dominic Stratten

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face
Congratulations - your first darlington transistor circuit :-)

Ahhhhh I remember back in the olden days .......

The reason you're probably getting an output with 3 transistors is a very
small leakage current from the 1'st transistor is amplified by the 2nd then
the 3rd to make your very small voltage into a rather larger one. try using
a very large (1 Mohm or greater) between the input and ground. This should
help stop any stray currents.


{Original Message removed}

2002\08\05@084953 by Olin Lathrop

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>>
Anyway, I'm noticing weird results with 3 transistors.. the LED fluctuates
in a dim state, even with the wires not touching.  Making *any sort* of
contact with the wire connected to the primary transistor's base will light
up the LED (quite brightly).  Don't even need to be near the +ve supply.
That's touching even the plastic insulation!
Anyway.. I don't know if this is called a transistor amp or what, but I was
just wondering why it does this.. am I naturally generating current? :D
<<

Your circuit now has such high gain that it is sensitive to signals picked
up from the environment, like 60Hz power line noise and radio stations.

Try this.  Make sure you are will insulated from everything else and touch
the wire.  The LED will light up because your body is much better at picking
up the stray signals than the little wire, and these stray signals are being
amplified.  Now touch circuit ground with the other hand.  The LED will
probably go off.  You may be able to adjust its brightness by how hard you
grip the ground connection.  Connecting your other hand to ground should
still work thru a small capacitor, like 100nF, proving that these are AC not
DC signals.

Another interesting thing to do would be to look at the waveforms after the
first transistor stage.


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2002\08\05@100550 by Shawn Mulligan

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Hey Kieren. Transistors are pretty cool, huh? -Shawn

>I thought I'd try an experiment based on a transistor;

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2002\08\05@135022 by Harold M Hallikainen
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On Mon, 5 Aug 2002 08:04:42 -0600 Shawn Mulligan
<spam_OUTmulliganshawnTakeThisOuTspamHOTMAIL.COM> writes:
> Hey Kieren. Transistors are pretty cool, huh? -Shawn
>

       Yes, they are! For an example of simple DC and AC circuit analysis of a
common emitter amplifier, see
http://www.hallikainen.org/cuesta/et113/CEamplifier.pdf .

Harold


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2002\08\05@153752 by Barry Gershenfeld

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>Anyway.. I don't know if this is called a transistor amp or what, but I was
just wondering why it does this.. am I naturally generating current? :D
>
>-Kieren

When you had one transistor, that was a transistor amp.  Two makes
a high-gain amp.  Three; now, that's called an oscillator :-)

Barry

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2002\08\05@170319 by Peter L. Peres

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It's called a darlington and it is sensitive enough that stray AC and
radio stations picked up by your body set it off. Try to power it from a
battery, go outside far from power lines and AM transmitters and touch it
again. It won't work.

Peter

On Mon, 5 Aug 2002, Kieren Johnstone wrote:

{Quote hidden}

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