Q&A
www.dicomse.com.ar/
In case you want to do a work-around using present-day MCU/logic
chips, here is a pinout of the
MM5314N:
http://users.otenet.gr/~ath
sam/Data_Base/MM5314N_clock
_alarm.htm
(the hex file) from the Nuts & Volts
website, my computer can’t open it.
Do I need a special program or
software to view this file? I sure
would like to see the code, as I am
interested in building the project.
Brian
via Internet
Cassette To PC
Q. I have a collection of vinyl
records and cassette tapes that I
would like to copy over to my PC.
However, my system is an older,
bookshelf stereo with no line-in or
line-out jacks. It does have a 1/4 inch
headphone jack, though, which I
plan to use.
If possible, I would like to listen
to the music while copying. How
much power is needed by the line-in
input of the sound card and how
much is needed by the headphones?
Do I need a circuit to reduce the
headphone signal?
Dean Hansen
New Lisbon, WI
directly feed the sound card line
input as long as you have a compatible patch cable (1/4” to 3. 5 mm
stereo, in your case) and adjust the
playback system’s volume control to
provide a solid signal without distortion. No special electronics are
required.
All you have to do is tap into this
line for monitoring — but it has to be
done without pulling down the line
with low impedance earphones.
What I suggest is a low power headphone amplifier — like the LM4808 —
to isolate the headphones from the
sound card. The chip is available
from Digi-Key. A typical circuit is
shown in Figure 6.
I’ve adjusted the values for 4. 5
volt operation — three AA cell
batteries, which you can replace with
a 5 volt wall-wart. Also, note that I’m
using R1 for the volume control.
Adjust it to your needs; the lower the
resistance, the louder the sound. Of
course, you have to supply all the
cable breakouts and end connectors.
RadioShack should have what you
need.
A. I’ve been monitoring a CD-ROM chat room for a while now
and have learned a lot about the
transfer of record/tape to a PC’s hard
disk. One thing I learned is that you
can use the headphone jack to
Project Needs PIC
Burner
Q. In the April 2004 issue, there is
a project entitled “Hand-held
Messenger” that seems very interesting to me.
However, when I
try to download
the file that contains the code
for the micro
+ 4.5V
To PC
Sound Card
Figure 6
100k
3.9k
2.2uF
3.9k
+
100uF
+
R1
10
LM4808
Headphones
2.2uF
3.9k
+
+
100uF
+
1uF 100k 3.9k
LEFT RIGHT
Audio Line Monitor
From
Stereo
A. When programming a micro-controller (or a CPU, for that
matter), you first create a source
code file. This file contains all the
instructions in computer-ese (
probably assembly or Basic) that you
can modify — or just read. However,
the microcontroller can’t read
computer-ese. It has to work with
binary numbers.
So, the source code is converted
into hex format, which the chip
understands. This is done using
another program, called an assembler or compiler. Once converted to
hex, all you can see (using WordPad)
are long ASCII strings of 0 through 9,
and A through F. At this point, you
can’t change the program without
going back to the source code, making the changes, and generating a
new hex file. (Don’t write — I know!)
Just having the hex code isn’t
enough. To get the hex file into the
microcontroller, you need a burner.
This is a piece of hardware that the
controller chip plugs into and connects to the serial, parallel, or USB
port of your computer. When you
run the burner software, the hex file
is transferred to the microcontroller’s
memory. You’re now set. PIC programmers are plentiful and include
F
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NUTS & VOLTS
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v
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1.0k
4.22k
Figure 7
+ 12.6V
6
FB .01 2 3 Vin Bst
LM2678 1
Sw
GND
4
12uH
+ 6.3V
+
470uF
50WQ03FN
+
100uF
Car Battery Downverter
34
SEPTEMBER 2004