Electronics Forum / Basics / May 2007

I just showed my son (13yrs) logic gates, and, or, nand, nor, xor, etc.
I'd like a few simple problems to solve using logic gates. Something he
needs to think about to make the logic work.
He will use http://www.uoregon.edu/~bsmith4/simcir121/simcir.html

I have a lamp near my bed that is controlled by touching a part of the
metal. I like it. Each touch brightness until it then turns off. However, it
has started turning on in the middle of the night. Anyone know what cause
might be? Does something wear out and need to be replaced?

if I build by my self a USB cable by 4 seperate coaxial cable
together , it's can work over 5 meter?

The usual explanation of a feedback oscillator goes like this. ""We have an
Amplifier 'A(w)', a feedback circuit 'B(w)'. An initial input v=Ke(jwt)
produses an output A(w)*B(w)*Ke(jwt) which in turn produces an output
(AB)^2 * Ke(jwt) ...... => If the signal is to be sustained ...

I'd like to tin one side of a 5/16" square copper bar so that it can
be soldered to a PCB.  A soldering iron isn't doing the trick, even
with lots of flux.  Any ideas?
Don

I found a book I would recommend to anyone who has an interest in
electronics.  The title is "Much Ado About Almost Nothing", a history of
electricity and electronics.  It has a novel approach in that it follows the
path of the electron (which is the "almost nothing" in the title).

I need to build a compact transformerless high voltage supply that
will run off of 120VAC mains and produce at least 2000-4000 (AC or DC)
volts with very low current. I figure what would be best is the
"Walton-Cockroft voltage multiplier"

Hi, I am having a little microwave experiment, and I want to shield some
 cracks from leaking microwaves. A friend said to me that a paper-type
called "mica" is used for such reasons in microwave ovens. Actually what
he told me is that it allows microwaves to pass through, but ...

Does anyone know what kinda motors that most drills use? I was thinking it
was a torque motor but not sure.
Also, for DC motors can I get away with changing the voltage to a lower
setting to increase the torque or do I run a huge risk of burning up the

I am trying to make a 5V mini relay switch when the HDMI indicator LED
in my DVD player lights up.
I have unsuccesfully tried to trigger the mini relay (5V, 40mA) via an
optocoupler (4N33 - infrared/darlington) "piggybagged" on the

I was just wondering if anyone knows what the analog video signals
going from the computer to the monitor look like or what they are
called.
Also, is there a microcontroller that could generate such signals?

I was hoping to get some decent info from this group, but the SNR is
way too high !
Are there many trolls here ?

I'll be needed to create a simple remote control system soon and I'm curious
as to my options(and I have no experience with rf).  I'm looking at rf pics
as they seem very simple but one thing I'm worried about is the range which
is, I guess, around 20-30 feet maybe(only ...

If you sort the thread below by date, using google. There is a post by
Moosefet at 109. It isn't showing up. The post number [109] and the
name [Moosefet] are there but the post isn't showing.
http://groups.google.com/group/sci.electronics ...

Group-
Not sure if there's anyone out there who has any experience with car
radios.  Specifically, have a '99 Chevy S-10 with a Delco AM/FM/CD
player installed.  There is a 9-pin connector on the back which is used