January 2018 63
masking tape over the lens of the
camera on his laptop. I think he’s
paranoid; he says he’s being safe. I’d
love opinions about which one of us
As they say, “Just because you're
paranoid, doesn’t mean that they
aren’t out to get you.”
#1 Actually, like your roommate,
I also keep tape over my camera
when I don’t intend on using it.
I’m not actually as worried about
someone hacking into it as I am
about accidentally turning it on
without knowing. It could be really
embarrassing to find out later that
your cam was on and someone was
watching via Skype or something
similar without you knowing.
Having someone hack into the
cam is certainly possible, but user
error is probably more likely. Either
way, why not be safe and blind the
camera when not needed.
#2 I hate to say it, but your
roommate is right.
As someone who builds gaming
computers for a living, I can tell you
that any computer that is connected
to the Internet can be subjected to
some sort of unauthorized access.
That’s why we have things like antivirus, firewalls, and other protective
With that being said, your
camera can very well be accessed
from the outside. Your roommate's
tape solution is common and works
effectively to keep unwanted eyes
from seeing what you’re doing.
However, you should know that if
someone has access to your camera,
they have access to your hard drives
You can make it harder for
someone to access your network by
having a WPK passcode instead of a
WEP passcode on your router, and
setting up a secondary computer as a
Hopefully I have answered your
[#10173 - October 2017]
Temperature Rise Of A Heatsink In
An Amateur Radio Transceiver
I recently did a “tear-down” of a
Baofeng BL- 8 battery eliminator (for
use with a UV82 dual-band tranceiver;
see www.hamguyparts.com, articles).
The tear-down revealed that the eight
volt battery eliminator actually used
2X L7808CV TO-220 voltage regulators
connected pin for pin in parallel,
which is somewhat unconventional.
Both regulators were mounted to
a common small ( 20 x 34 x 1.8 mm)
aluminum heatsink and all enclosed
within the plastic housing which was
sized to resemble the battery it was
In the ideal case, each regulator
would carry 1/2 the total maximum
current taken by the transceiver, which
is approx. 0.775 amps. Each regulator
produces a nominal 8.0 volt DC
output and has to dissipate approx 4. 6
watts of heat. The thermal resistance
of the TO220 package is 5°C per watt,
junction to case (or mounting base).
They are mounted dry, which
adds another 1°C per watt for
mounting the base to the heatsink.
Q1: What is the temperature rise in
the aluminum plate?
Q2: Since there is no direct path to
air, what further temperature rise may
take place inside the plastic housing?
I searched my hard disc and
found a chart for thermal resistance
vs. heat sink area for a 1.5 mm
thick heat sink; 1.8 mm is not much
different from 1.5 mm, so I will use
that. This chart ends at 500 sq cm,
so I will extend the line and estimate
that the thermal resistance is 2°C per
watt. I'm also assuming the thermal
resistance is in deg C/watt since it is
not otherwise labeled.
Since the dissipation is 4. 6 watts
per TO220 and there are two of
them, the power to the heatsink is 9. 2
watts. The heatsink area is 34 x 20 =
680 sq mm. The temperature rise in
the heatsink is: 2°C/watt x 9. 2 watts
= 18. 4°C. The temperature rise to the
junction of the TO220 is: 6 deg/watt
x 4. 6 watts = 27. 6°C. Adding these
together, the junction of the TO220
will be 46°C above the heatsink
temperature which will be above the
ambient of nominal 25°C.
It is not possible to estimate
the further rise of the heatsink due
to lack of air circulation without
more information such as size of the
enclosure, thickness of the plastic,
thermal resistance of the plastic, etc.
[#10174 - October 2017]
Should I Switch?
I’m torn between using 3. 3
and 5.0 volt components on my
microcontroller projects. Many
people seem to be moving to 3.3V,
but components don’t seem to be as
readily available as 5V components.
What are the advantages and
disadvantages of each?
#1 In my view, that is not really
an up-front issue. If I want to build a
logic circuit, I have an idea of what
I want it to do. Then, I start looking
for the required parts, making a list of
what parts would work, and some of
the basic specs such as its operating
voltage, cost, footprint, availability,
Sometimes most of the required
parts are only available in 3.3V, and
the decision is made. Sometimes they
are available in 3. 3 and 5V, but the
3.3V version is some difficult package
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