Electronics Forum / Basics / February 2007

I want to build this PWM circuit, and I have no
100k pot. Can I substitute a 10k pot and a 1uf
cap for timing, or are there other things I
need to consider in this circuit?

When a system is driven by a wave at its resonant frequency, how does
the shape of the wave come into play?  For instance, will a square
wave at a resonant frequency have the same effect as a sine wave at
that frequency?

After listening to the RF interference radiated from a PDA on a
portable radio it got me to thinking. When pulses are sent down a wire
the wire will radiate RF. A lamp cord plugged into the wall radiates
RF. But does a wire carrying DC doesn't radiate RF, does it? What is

Greetings All,
I have a setup where I'm using Allegro P/N 5804B
(http://www.allegromicro.com/datafile/archive/5804.pdfto )drive a
stepper motor. It works well and can handle higher current than the

i have a Control Transformer with 240V on the primary, with 24VAC out the
secondary. My question is what would happen if i try to use this as a power
transformer using only 110/120V on the primary?

I have a 12 volt dc 690 rpm permanent magnet motor that I'm wanting to
use as a wind generator. The problem is that when I spin the shaft at
15 to 20 mph it produces 30 to 45 dc volts. I would like to regulate
it down to a constant 14 volts or figure out how to convert it to ac

Let's say you have a closed loop power control system that is making
adjustments every second proportional to the error from a target.
Also,
the readings it gets are delayed by ten seconds.  For what values of

I have bought some AA Nimh batteries and find that they are vary
slightly bigger than standard alkalines. I'm talking about a
millimetre or two and not much more, but it's enough to make them an
extremely tight fit in devices that have two batteries stacked on top

i was wondering whether a pc monitor bought from America would work in
the UK.
thanks.

Just bought a generator and it failed within two hours of usage. Mfg. say
maybe capacitor and will ship a new one. But am not sure. I have a voltmeter
with capacitor readings. Know how to test for resistance and voltage but
never tried to test a capacitor. I know the circuit should ...

I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal.  I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the

I have these 110VAC single phase small AC motors which are driving a
bunch of gears and other parts. Every now and then they will jam up
for one reason or another.  They will sit there and fry and I will
have to change the motor out.  So my question is can I put a in-line

1) is there a resource on the 'net that has
diagrams of the various semiconductor case types?
I mean like the old TO-series stuff, to the new
SMT cases. I'm trying to ID an old part I found,

is there any possibility that I can measure AC power line voltage
using PICmicro A/D?
Can some one gives me some direction? Can it be done?
I would like to measure AC voltage directly connecting to A/D pin with

I need some help.
After several years retired and many more years away from cobbling together TTL and field
programmable parts,
I'm trying to get my hands dirty again on a project.