TECHFORUM
READER-TO-READER
>>> QUESTIONS
buffers into individual files and keep
recording.
Heating Element Control Circuit
coil modes and various loading values;
78 RPM records need many different
equalization techniques.
I’m looking for a control circuit
(120 AC) for an electric smoker
heating element that doesn't have the
wide temperature swings a normal
thermostat controller has. It would
need to be rated to at least 15 amps.
For example, using a 210-220F range:
I thought about using MP4 DVR
units or digital cameras with video
record capability, but each has their
own shortcomings. Any ideas?
#8103 John Duncan
Indianapolis, IN
Here is something a bit easier on
the wallet: www.ramseyelectronics
.com/cgi-bin/commerce.exe?preadd=
action&key=US100.
MSN Direct
1. Below 210F — Heating element is
at full power.
2. Between 210-220F — Power
ramps down as the temperature nears
220F.
My coffee maker works off the
MSN Direct signal. Two more years
and MS turns it off. Is there a way to
build the FM generator with the time
in the signal so my coffee maker can
at least wake me up with coffee
already brewed?
If you’re really interested in building
a product from scratch, see www.semi
conductorstore.com/cart/pc/viewPrd.a
sp?idproduct=42808. Here is what you
asked for, a kit: www.hagtech.com/pdf/
ripper.pdf. There are a lot of choices.
Ron Dozier
Wilmington, DE
3. Above 220F — Heating element is
off or at the lowest power setting.
#8101 Curt Timmerman
Big Lake, AK
#8104
Jimmy Rogers
Jacksonville Beach, FL
ADC To Control Motor Speed
How does the ADC circuit control
the speed of a motor?
>>> ANSWERS
[#3102 - March 2010]
#2 In order to transcribe phonograph
disks to digital computer files, you will
need two devices: an analog-signal
stereo preamplifer with an RIAA transfer
characteristic and a stereo analog-to-USB
converter. The project ought not to cost
you a mint.
I know that it samples the EMF
from the motor and feeds it back via a
comparator. If it is going too fast, how
do you slow it down? I just built a
motor control module that can control
or feed back the EMF from 001 to
255. I would expect that it goes
through a DAC circuit and feed
back to the motor. But how? The
motor circuit has two connections:
a) PortB bit 0: Turns on the motor.
b) PortA bit 1: Feedback circuit that
samples the EMF voltage.
Convert Old Record
Player To Record To USB
I have a stack of records from the
‘50s, ‘60s, and ‘70s, and two record players. I saw a device in a store that would
record your records to USB. Can't I build
my own? Any suggestions?
A review of seven inexpensive preamplifiers — priced from $13.50 to $77.99
— can be found at www.audioxpress.com
/reviews/media/403hansen2090.pdf.
The reviewers did not seem to find a
linear relationship between price and
quality. The RIAA preamplifier transfer
characteristic is needed to compensate
for the nonlinear output-voltage-with-frequency characteristic of the magnetic
phonograph transducer.
When I press 010, it slows it down;
when I press 000, it slows it down more
but it is still running — why?
#8102 Frank Gutierrez
Clovis, CA
Automotive Black Box
#1 This depends on how much you
value your time and how much of an
audiophile you are. Remember that
software may be needed to remove
pops and create tracks, as well. For
approximately $30, you can buy a
device, software, and an RIAA preamp.
Is it worth it? See www.zzounds.com/
item--BEHUFO202. If you value your
audio, an RIAA preamp can cost you
big bucks such as the one found at
www.audiophileproducts.com/korora.
It includes moving magnet and moving
The stereo analog-to-USB converter
function can be provided by an EasyCap
model SINOSV3529 which can be had
for about $15. It will not only convert
stereo audio signals but it can also convert analog video signals having a composite video input and an S-video input
with NTSC or PAL format compatibility.
Peter Goodwin
Rockport, MA
I’m trying to design an automotive
black box that will record four
cameras facing the front, rear, and All questions AND answers are submitted by readers and NO GUARANTEES
each side in a 'ring buffer' fashion onto
Flash memory. The buffer would not
by Nuts & Volts readers and are intended WHATSOEVER are made by the publisher.
to promote the exchange of ideas and The implementation of any answer printed
need to be very large; five minutes
provide assistance for solving technical in this column may require varying degrees
problems. Questions are subject to of technical experience and should only be
would work. When a button is pushed
editing and will be published on a attemptedbyqualifiedindividuals.
or some other external trigger occurs, space available basis if deemed suitable Always use common sense and good
the box would save the four recording by the publisher. Answers are submitted judgment!
78 August 2010
