62 March 2017
READER - TO - READER TECHFORUM
Getting Started With High Voltage
I would like to experiment with
high voltage projects, but all my
experience in building power supplies
is for low voltage (typically 5 or 12
volts). I’d love a schematic for a high
voltage power supply that could
produce between 0 and 250 volts
safely. Also, any safety pointers for
getting started would be appreciated.
#3171 Ed Warren
Reliable Voltage Source
I am designing a battery powered
circuit that requires a very reliable
voltage source. I was considering
using a zener diode in series with a
resistor across the power source and
then tapping it at the diode/resistor
for the power point, but it seems
this would be very wasteful for the
battery. Would I be better off with a
linear regulator like an LM317 and
if so, would it create as accurate a
#3172 Gilbert Kreps
I need help with a circuit design
to flash a 10W laser diode at 14 Hz.
A crystal controlled 555 IC is too
variable due to temperature, and must
No microcontrollers please; too
complex and require coding. I need a
simple discrete design.
The problem is laser diodes are
pulsed with a tiny duty cycle, so they
must be pulsed at high PRF to create
the 1/28 second ON cycle. Probably
100 kHz for 1/28 second, off for 1/28
second, repeat ...
It may require multiple laser
diodes, interleaved ON pulses to
smooth out the 14 Hz ON cycle.
I basically want to emulate as
close as possible the 14 Hz square
To top it off, this needs to run off
the “dirty” rectified 6-12 VDC from a
As an alternative, instead of laser
diodes, an array of LEDs, perhaps 6
x 6 ( 36 LEDs) may be acceptable to
simplify down to just a 14 Hz crystal
controlled strobe timer.
The whole thing needs to fit in a
garage door opener sized box.
#3173 Tom Uryga
Surround Sound Questions
I recently upgraded from an older
two-channel stereo system to a 5.1
surround sound receiver. I have left,
right, center, and sub woofer speakers
set up at the front of the room, but
no easy way to run wire for the rear
What’s the best DIY wireless
method to get my surround sound to
the back of the room?
Does someone have a schematic
for a stereo transmitter/receiver
that I could build? Would using a
combination wired and wireless setup
have any issues with syncing the front
and rear channels?
#3174 Dustin Quintanilla
San Luis Obispo, CA
[#11161 - November 2016]
After the recent “forced” update
to Windows 10, I am so frustrated I’m
thinking of downsizing to the smallest,
simplest computer I can manage.
Has anyone successfully replaced
a desktop PC with a Raspberry Pi?
#1 I know some people who use
Pis as their main computer. However,
be aware that they are designed to
“Raspberry Pi” version supplied),
and they are not designed for heavy-duty use (i.e., games, audio/video
processing, etc.). If all you need is a
basic machine for Open Office and
light web use (i.e., check email), then
a Pi could be what you want. Do a
web search regarding Raspberry Pi
accessories (there are many!) and
application use to further see if a Pi
based machine is for you.
#2 As much as I am liking my new
Raspberry Pi 3, I am not ready to
ditch my (Windows) computers and
go all Pi. The OS seems very skinny
on error handling. One ends up in the
command line all too quickly. While
the included LibreOffice performs
okay, I feel a much better choice is
Ubuntu if making the switch from
Windows. Or, consider a refurbished
Windows 7 machine which are
plentiful. The Pi does quite fine for
web browsing, but when it hiccups
things get obtuse very fast.
#3 I attempted to use a Pi for
a desktop and it works, sort of. It
was okay for web surfing but had
some trouble with videos and other
complex pages. Almost everything
had some limitation. It worked great
as an Internet radio streaming device
though, and that is where it lives now.
You also have to have a monitor
with an HDMI or composite video
(with an adapter with Pi 3) input, and
by the time you buy all the pieces you
need to make it work, you have spent
a few bob.
Linux is the solution. Linux Mint
I have been basically Windows