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READER- TO-READER TECHFORUM
I would like to install a backup
alarm on my ‘07 Mazda Miata with
the Mazda jingle (ZOOM ZOOM). I
can get the jingle from You Tube but I
don't know if it's possible to erase the
sounds on a current backup alarm and
install the jingle, or build an entirely
new alarm. Are there any plans,
diagrams, etc., available?
#8111 John Mierta
Las Vegas, NV
Recycle Old Answering Machines
Is there anything I can do with
my old answering machines? Newer
electronic machines are available at
low prices and must have important
parts or uses!
Analog S Meter
I have a vintage Realistic DX-400
shortwave radio. The signal meter
finally gave out after all these years. I
would like a small circuit to fit in a
small confined space, using a 10
bargraph LED. The bargraph should fit
perfect in the small window where the
needle meter once was.
#8113 Frank S Barren Jr
I am moving from through hole
PCBs to surface-mount technology
and am looking for a nominally cost-effective way of doing reflow soldering. I would prefer a solution better
than a toaster oven. Are there inexpensive reflow ovens (under $1,000)
All questions AND answers are submitted
by Nuts & Volts readers and are intended
to promote the exchange of ideas and
provide assistance for solving technical
problems. Questions are subject to
editing and will be published on a
space available basis if deemed suitable
by the publisher. Answers are submitted
78 August 2011
that you can suggest or recommend? I
imagine this is something many Nuts
& Volts readers would love to know!
#8114 Joe Menard
Optical Speed Measurement
I want a camera-like device that
can measure the speed of a surface
that is passing by. The passing surface
is moving perpendicular to the focus
plane at some modest speed TBD by
sensor element speeds, I suppose. For
example, this little camera looks at a
piece spinning on the lathe and
reports "five meters/second surface
speed." To do this, the device has to
be able to detect the speed of a
moving image pattern falling on the
sensor array. If we can detect that, we
can calculate the speed of the actual
object using focal length and distance
of the surface. However, the light
readings from the sensor array
would need clever measurements to
determine the speed.
Scotts Valley, CA
[#4115 - April 2011]
LED/LCD Digital Counter
I am looking for a fairly large ( 6-8
or 10-12 inch high) LED or LCD, two
digit, digital display which could be
changed by using perhaps one button
to increase (by one at a time) and one
button to decrease the displayed value,
i.e., 00 to 99.
It also would be good to just use a
numbered keypad to enter the value.
Another useful feature would be
by readers and NO GUARANTEES
WHATSOEVER are made by the publisher.
The implementation of any answer printed
in this column may require varying degrees
of technical experience and should only be
attempted by qualified individuals.
Always use common sense and good
to turn on and off (flashing at a chosen
rate) the display to indicate urgency.
This is to be in an office area
where they are serving the public.
Most of you have been where there is
a service counter and you need to
"take a number" to secure your place in
line. Often, they will have a "Number
Being Served" display to show you
where you are in line.
Well, my application would be to
enable the employees (they can see
the display from a distance at their
desks) to view how many people are
currently waiting to be seen. If there
are not so many, the employee can
afford to give the customers a bit more
time if needed or if very busy, will have
to keep the visit as brief as possible.
Right now, they are using an old
mechanical flip-number type display
which is a rather awkward (and not too
state-of-the-art method) way to do it.
An employee is continually jumping up
from their desk (interrupting their work
and time) to change the sign.
I would like to learn what the
circuit design could be and what
components are needed so I could
construct it myself.
Here is a circuit (Figure 1) that will
help prevent an employee from getting up to push buttons on the display
or running several feet of wire to a button controller. The circuit has been
designed and tested to work with a
$10 remote control car. Remove the
receiver from the car and disconnect
the motors and battery pack. Wire the
motor connections from the receiver
to the circuit. Each motor connection
has two wires and each wire supplies
a signal to the circuit. I used the for-ward/back motor connection for the
up/down counters and the right/left
connection for the reset/flash functions to make the remote easier to
understand and operate. Supply
power to the receiver with U1.
VR1 allows you to control how
fast you want the display to blink. The