Electronics Forum / Basics / January 2007

I am interested in building an LED array with about 40 LEDs. They take
3.3 volts at 20mA.
Does it make sense to make 20 arrays of 2 in series with a 150 ohm
resistor, and connect all of those in parallel to a 9 volt battery?

I have a electronic load powersupply tester and was wondering how you
go about setting it up?  For a computer powersupply how would you set
it.   Do you set the resistance and for how much?  How do you figure
this out.  Just measure the inputs on the computer?   Does that give

Let's say an incandescent light bulb is controlled by a rheostat.  Does
a rheostat truly save power when set to low power?  Or, is the same
amount of current going through the rheostat regardless of the power
setting?

I am just starting out in electronics as a hobby.  I learnt Ohms law
i.e. V=I * R
Now just say I had a 1.5 Volt battery (AA cell) and an 1 ohm resistor
So given Ohms law - to find the current

I am trying to build a circuit that sets a few small DC outputs.  Some
of these will need to be tuned from negative to positive, pretty much
over the range from -1 V to 1 V.  I figured a variable voltage
regulator and a good pot would be able to do the trick, as we have both

I am building one of these http://plazma.kapsi.fi/diy/lanc_controller/
Its a LANC Controller (ie. remote control) for a Sony camcoder.
The project uses a PIC16F84A chip, which is a programmable
microcontroller.

I am looking to replace a transformer for a rechargeable razor which was
plugged into 220V by accident, not me the kid. It's marked
File:0326-3501-01
I/P 120V O/P 3.8V 110mA

Some people here kindly helped with a silly question. I have perhaps
another.
Trying to understand spice models to make a new model for ltspice. Not
understand so looked at existiing ones. Spice model to Fairchild

I m looking for some ideas of applications where I can use my old
batteries, before recycle them.  I allways get batteries with still some
power but who aren't good enough to do some usefull and reliable stuff.
I was heading to look at some charge pump chips ...

Logic Friday is a new freeware tool for combinational logic analysis,
minimization, and gate synthesis. You can enter a logic function as a truth
table, equation, or gate diagram and minimize it with espresso. You can
automatically generate a multi-level gate diagram using ...

What would happen if you connect 2 resistors together in series and
then connected a capacitor also in series (say to the end of the 2nd
resistor).  What will happen to the voltage divider?  This is a DC
circuit.

Hey everyone,
I am an undergrad in ECE and I am working on building the box for a
double vented 500W subwoofer.  I want to light up the inside with some
kind of blue light so that it shines out the side (thick clear

I am working on a PCB design for our test site, which contains 100pads
and more than ten RF circuits with more than 50 RF I/Os. We have 12
types of VDD and two types of GND on this chip. I am thinking about
using a 6 layer board, signal, GND1, VDD, VDD, GND2, signal. However it

This question arose from the typical "what do I do to protect an op-
amp when the input voltage is higher than supply?"
In a typical non-inverting configuration the answer seems straight
forward since the input will be at the non-inverting pin of the IC.  

I have a wood shop in my basement and would like to automate the
startup/shutdown of my dust collector unit.  It is a 220v unit plumbed
to 4 separate power tools (3 are 110v, 1 is 220v).  My ideal
configuration would be to have the dust collector start immeidately