LMC6082 is a dual, I used the second
op-amp in a low-pass filter so the
average voltage can be measured.
The capacitors should be film type for
accurate results. The internal offset of
the op-amp is less than 1 mV, so I
assumed that was neglectable.
[11037 - November 2003]
Does anyone know of a simple
data logger I can use to record the
time and date of each instance a
switch is turned on and off and
keep it in memory?
coin cell that can easily be popped
out of its holder. Some, quite possibly
yours, will have a three-cell battery
which is soldered in place near the
edge of the motherboard. If this is the
case, then look for a small header
with three pins and a shorting plug
near the battery. Moving the shorting
plug to the opposite set of pins will
disconnect the battery from the
CMOS backup memory. In all cases,
be sure that the power to the
computer is off, otherwise the backup
memory will be powered from the
main supply and disconnecting it will
have no effect.
[110310 - November 2003]
I need a circuit that will track a
changing voltage (+0.1 to +0.9 V)
and allow me to use a
potentiometer to create an offset of
± 0 to 3 millivolts and adjust to an
average of 0.45 V. This circuit is to
track the output of an automotive
The H06-001-02 Hobo™ Data
Loggers from Onset will record up to
2,000 different changes (on/off) and
the time each happens. They require
the BoxCar 3. 7 (BC3.7-DL) software
to download the information. This
system was very user-friendly for me.
Both should be at www.digikey.
In this circuit (Figure 1), the
LM78L05 provides isolation from the
noise on the 12 V supply. The U1A
amplifier circuit has unity gain for the
input signal and the ± 5 volts that is
available at the pot. You should use
1% resistors for accurate results. The
MAX1681 is a + 5 to - 5 inverter; use
film or ceramic 1 mF caps. Since the
[12031 - December 2003]
What is the difference between
an S-video input and the plain old
video input on a television set?
NUTS & VOLTS
An S-video cable is a higher
grade of the plain old composite
video input. The difference between
the two is that S-video provides more
bandwidth to the TV set. There are
basicially two feeds coming in at
once, chrominance and luminance
(or color and brightness) and that's
why there are four pins.
When using S-video, there is
better picture quality. To put it in
easiest terms, a data path for color
and a path for brightness — where
composite video has to accomodate
for both and the picture sometimes
looks "washed out".
Video quality for home users is,
from best to worst: fiber, component
(RGB), S-video, composite video, and
RF (audio and video AKA cable feed).
[110311 - November 2003]
I want to build a current
Circle #34 on the Reader Service Card.