the cost of energy is a concern. The
four scenes and off modes are
selected by a momentary contact
closure. The manufacturer solution is
to upgrade to digital control. Is there a
circuit design using a microcontroller
that could capture the state the
controller was in at the time of the
power failure and restore the
controller to the mode after power is
BASIC Stamp Help Needed
I am a beginner using a Parallax
BASIC Stamp kit #555-28158. How do
I wire seven LEDs and program them
to come on and off in certain orders
or patterns? Is it possible with this kit?
Long Range Wireless RS-232
How can a long range wireless
RS-232 link between two computers
be built? I'd be very interested in how
to get an effective range of 3-5 miles.
#11118 Todd Norvell
I was wondering if it would be
possible to cheaply build a system in
which I speak into a CB type radio,
and have the signal sent to a loudspeaker about 1,000 feet away or
slightly more? The current system I
have is a bullhorn, and I have to stand
a good distance back from the crowd
to accomplish my task. It kills my
voice. I was thinking if I could buy a
loudspeaker (what wattage?) and a set
of CBs that I should be able to modify
the other CB to feed into the amplified
loudspeaker so I can simply talk into it.
Surely there is a commercial
version, but I'd like to be able to do it
on the cheap if possible.
#11119 Daryl McIntire
used as a "Recording" light in a small
studio. Ideally, the sign would come
on fully for several seconds at first, and
then flash on and off slowly, ramping
the voltage to the display or LEDs up
and down, so as to create a soft blinking display.
#111110 Al Parry
“Suppose you want a microcontroller (MCU) to adjust the intensity of
LED light. You could use a motor to
turn a potentiometer that adjusts a
transistor's base current, but that
approach doesn't make sense, and
many MCUs offer a better way to
Those MCUs include at least one
pulse-width modulator (PWM) output.
This output creates a signal that varies
between, say, three volts and zero
volts at a preset pulse period, as
shown in Figure 2. Software varies the
pulse width. If the MCU creates a
PWM signal that looks like a square
wave, the voltage exists at three volts
for 50 percent of the time and at
ground for 50 percent of the time.
The MCU can adjust the pulse
width — thus it modulates the pulse
width — so you could have a series of
pulses at three volts for 10 percent of
the time and at ground 90 percent of
the time. The percentages of on and
off times always add to 100 percent.
If you use this signal to control a
transistor that operates as a switch,
the LED would turn on only 10% of
the time. Because your eye cannot
respond quickly enough to the
frequency of the pulses, the LED
simply appears dimmer.
You can use a MCU such as the
Microchip Technology PIC16F690 in
the PICDEM Lab Development Board
kit (DM163035) to generate a PWM
signal controlled by software. Then, a
program will vary the brightness of
one or more LEDs between off and
Here's an overview of how to use
the 16F690 PWM signal "generator."
This description applies only to this
MCU. Other MCUs also have PWM
sections, but require different settings.
>>>YOUR ELECTRONICS QUESTIONS
ANSWERED HERE BY N&V READERS<<<
[#10111 - October 2011]
What is the easiest or best way to
PWM a PIC16F690? I've seen Chuck
Hellebuyck's book, but he uses an
external pot to manually do it. I need
to do it in software.
I have posted an 11 page PWM
tutorial, complete with code for the
16F690 as it relates to driving an LED.
I hope this helps.
Following is an excerpt from Jon’s
excellent tutorial. Download and read
the full document for the complete
Building a "Recording"
I'd like a circuit to power LEDs or
an electro-luminescent display to be