Electronics Forum / Basics / June 2007

Anyone know of a good relay board, that can be interfaced from a mcu
using either 1digital output (20ma max, or if need be I can include the
transistor) per relay, or simple serial comm at low baud rate.
Should run and trigger at 5VDC.

Video signals for NTSC, PAL, and SECAM television are transmitted on
AM carriers.
My question is, let's say I have a television set that is capable of
receiving and demodulating FM video carrier waves. What would I see on

applications?
phase modulation (PM(AM*FM)) -> actional modulation (AM(h) = h')
amplitude modulation (AM(v)) -> potential modulation (PM(u) = u')
frequency modulation (FM(f)) -> durential modulation (DM(t) = t')

I'm doing some work where we will need about 20 to 40 5V battery packs
and I'm trying to figure out exactly what to do...
Our restrictions include:
Getting 4.8V is probably okay, but 4.5V won't work -- we need to stay

I have a strobe light which has a xlr input for a 10v trigger.  I want
to get this to flash in time to some music, I thought i could make a
cuircuit which would high pass a audio signal so i just get the hi
hats / cymbols and use this to switch a 10v charge.  I dont have much

Can anyone suggest a source of Allegro's UCN 5804b translator/driver
chip (preferably in Australia but anywhere that will ship overseas is
ok).  I know this chip is no longer manufactured but I understand
sizeable stocks are being held.  I only need 3 of them!

my name is george (yioryos in greek) dimitriadis, and this is my first
post.
I would be grateful if everyone is interested to reply to my post and please
excuse me for any

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I have a line cord with black, white and green conductors. I wish to
use it to connect to a 250V plug. Except for the green ground, does it
matter which of the other two are connected to which terminal? The
screws do not have the bronze and chrome colored screws. Both are

Why are so many caps spec'ed as 0.047 uF or multiples thereof, thanks

When various textbooks explain the operation of a p-n junction or a
diode, they usually do not talk about metal contacts. That is usually
a separate topic. But let's consider the whole thing together since
this the only way the diode can operate and let's assume that both

A man named David Reid has figured out a way to melt small
quantities, up to .25 kg, of silver and other non-ferrous metals, in a
microwave oven. He describes his method here:
http://home.c2i.net/metaphor/mvpage.html

I used to have a Sony cassette recorder in the early 80s that if you
wore headphones and pressed record, you could literally here a pin
drop in the room. I took this apart back then and the circuit for this
used a 741 op amp chip. I have some of these and have found some

Why characteristic impedance of transmission line isn't important at
low frequencies (1000kHz) and it is one of the main parameters in RF?
At high frequencies if  a generator isn't matched  with the impedance
of the line the reflection of the power can damage the genarator, why

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