This is only a preview of the July 2012 issue of Silicon Chip. You can view 27 of the 104 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "Soft Starter For Power Tools":
Items relevant to "Wideband Oxygen Sensor Controller Mk.2, Pt.2":
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Advertising Index
Altronics.................................. 72-75
Amateur Scientist CD................... 63
Bitscope......................................... 9
Electronex...................................... 5
Emona Instruments...................... 45
Futurlec.......................................... 6
Geoff Coppa............................... 103
Grantronics................................. 103
Hare & Forbes.......................... OBC
Ask SILICON CHIP
. . . continued from p102
viously you can’t measure the SPDIF
frequency directly as the clock and
data are encoded on the one signal and
would vary, depending on the data. (S.
G., Carnegie, Vic).
• You are right; computers will often
down-sample the audio to 44.1kHz/
48kHz 16-bit for various reasons. The
main one is so that several applications
can play sounds simultaneously and
these are mixed in software, at a fixed
sampling rate and bit depth.
Some sound drivers let you set/
query this information but you can
measure it at the DAC. The left/right
clock is output from the LRCKO pin of
IC3 (pin 10) and this is a square-wave
with a frequency equal to the sampling
rate. It connects to pin 10 on the digital
I/O header and thence to pin 4 of IC6
(PLRCK). You can measure this with
a frequency counter or scope.
Unfortunately, there is no easy point
to probe this line since it runs only on
the underside of the two PCBs. You
could solder a short length of solidcore wire to pin 10 of one of the 16-pin
IDC sockets and have it stick out from
under the board and you could then
measure the frequency, relative to a
convenient ground point such as a
regulator tab or power supply ground
terminal block screw. This short length
of wire should not interfere with the
operation as long as it doesn’t short
to anything.
There’s no easy way to tell whether
your sound card is outputting data
with a 16-bit or 24-bit resolution.
You can connect an oscilloscope or
logic probe to the serial audio bus
and monitor the serial clock and data
104 Silicon Chip
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PO Box 631, Hillarys, WA 6923
Ph: (08) 9307 7305 Fax: (08) 9307 7309
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High Profile Communications..... 103
Instant PCBs.............................. 103
Jaycar .............................. IFC,49-56
Keith Rippon............................... 103
Kitstop............................................ 6
LED Sales.................................. 103
Notes & Errata
Crystal DAC (February 2012):
the trimpots were specified as
500Ω but should in fact be 5kΩ.
This affects the circuit diagram,
PCB overlay and parts list. Also,
the labels for Q22 and Q23 are
swapped on the overlay diagram
(Fig.6, page 32).
Crazy Cricket/Freaky Frog (June
2012): the Jaycar buzzer part number is incorrectly listed in the parts
list. It should be AB-3440.
Wideband Oxygen Sensor Controller (June-August 2012): the
parts list in part 1 (June, p42)
includes two 3.5mm stereo jack
plugs. Delete these and substitute
two PCB-mount 3.5mm stereo
switched jack sockets.
lines. There are 32 serial clock pulses
per sample sent; if the audio data is
16-bit, the data line will always be zero
half the time whereas if it’s 24-bit, it
will be zero for eight pulses in a row,
ie, 25% of the time.
Finally, it may be possible to get a
general idea of the sampling rate from
the S/PDIF frequency, especially if you
are playing a silent file. The S/PDIF
frequency is typically somewhat proSC
portional to the sampling rate.
Low Energy Developments........ 103
Matrix Multimedia......................... 93
Microchip Technology................... 21
Mikroelektronika............................. 3
Oatley Electronics...................... IBC
Ocean Controls............................ 71
Quest Electronics....................... 103
Reality Design.............................. 10
Red Button Technologies............. 11
RF Modules................................ 104
Roc-Solid...................................... 43
Sesame Electronics................... 103
Silicon Chip Binders..................... 62
Silicon Chip Bookshop................. 95
Silicon Chip Order Form............... 97
Silicon Chip Partshop................... 96
Silicon Chip Subscriptions........... 89
Siomar Battery Engineering....... 103
Splat Controls............................. 103
Tenrod Australia............................. 7
Truscotts Electronic World.......... 103
Verbatim....................................... 41
Wiltronics........................................ 8
Worldwide Elect. Components... 104
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