Advertising Index
Altronics.................................29-32
Blackmagic Design....................... 7
Dave Thompson........................ 103
DigiKey Electronics....................... 3
Emona Instruments.................. IBC
Hare & Forbes............................. 11
Jaycar.................. IFC, 12-13, 44-45
Keith Rippon Kit Assembly....... 103
Lazer Security........................... 103
LD Electronics........................... 103
LEDsales................................... 103
Microchip Technology.............OBC
Mouser Electronics....................... 4
OurPCB Australia.......................... 5
PCBWay......................................... 9
PMD Way................................... 103
SC Micromite Explore 40............ 56
SC Mains Sequencer................ 103
Silicon Chip Shop.................97-99
Silicon Chip Songbird................ 52
Silicon Chip Subscriptions........ 53
The Loudspeaker Kit.com.......... 10
Wagner Electronics..................... 85
YUKI KP-480 machine.............. 103
we don’t think that is possible unless
the clock provided by the master is
quite slow.
For example, we used a Raspberry
Pi Pico running at 133MHz+ to create
an I2C monitor device to capture the
output of an I2C OLED, to emulate
its display. Even then, the I2C master
needed to be slowed substantially to
capture the data successfully.
The immediate output behaviour is
normal since the Interface Board delivers the data as soon as it is received.
Something like the Arduino IDE’s
serial monitor will only send data
when the line ending is entered, so
that is an option if you want such
behaviour.
Protection diodes on
amplifier outputs
Regarding Electronic Australia’s
Playmaster and Silicon Chip’s audio
amplifiers, I am curious why there
are no back-EMF protective diodes
connected between the emitters and
collectors on the output transistors.
They are used with many commercial
amplifiers, including Naim, Denon etc.
I have assembled many EA and
Silicon Chip amplifiers over many
years for friends and myself. (D. B.,
via email)
● We have included such diodes in
most of our amplifiers since November 2012, when they were used in
the Classic-D amplifier (siliconchip.
au/Series/17). Since then, they can
be seen in the Ultra-LD Mk.4 amplifier from August 2015 (siliconchip.
au/Series/289), the SC200 in January
Errata and on-sale data for the next issue
2017 (siliconchip.au/Series/308) and
the 500W Amplifier from April 2022
(siliconchip.au/Series/380).
These diodes are necessary when
the amplifier is used to drive a transformer, as used for 70V and 100V line
connected loudspeakers. The diodes
are not strictly required while the
amplifier is operating within its linear
range, where the negative feedback has
control of the amplifier output.
Only when the amplifier is in clipping, where the output operation is
beyond the limits of feedback control, will the protection diodes come
into effect and clamp any back-EMF.
This only occurs when the amplifier
is used with a significantly inductive load.
Our earlier amplifiers without the
protection diodes were long-lasting
and reliable. Including these diodes
in later designs is part of the evolution
of semiconductor power amplifiers,
beginning in the Electronics Australia days in the 1960s.
With continued improvements
over the decades, our amplifiers have
become some of the best performers
ever published, rivalling the best commercial amplifiers.
Generally, including these diodes
doesn’t seem to hurt and they may
be beneficial in some circumstances.
Earlier amplifiers would have omitted them due to their cost, but these
days suitable diodes will not break
the bank, so we might as well specify them.
DIY inverters are no
longer worthwhile
Next Issue: the August 2025 issue is due on sale in newsagents by Monday, July
28th. Expect postal delivery of subscription copies in Australia between July 25th
and August 15th.
I saw advertisements in two old
issues of Silicon Chip for 24V DC to
240V AC inverter kits from Altronics.
I also found an old Rod Irving kit for
a 2kW 24V DC to 240V AC inverter
from 1992-1993. Are there more recent
projects for inverter kits? (R. S., Chifley, NSW)
● While it may have been worthwhile to build your own inverter back
in the early 1990s, today it definitely
isn’t. Basic commercial inverters can
be found under $30. A 150W inverter
will cost you around $50, while $99
will get you a 400-500W inverter. You
can get a 2kW inverter for under $200
from many sources.
Anything we design would cost
more than that in just parts, and you
SC
would still have to build it.
Australia's electronics magazine
siliconchip.com.au
Vintage Radio – Emerson 888, May 2025: there are two mistakes in the
redrawn circuit diagram (Fig.1). R6 is shown connected to the wrong end of
T2’s secondary; it should connect to the lower side that goes to the base of
TR2. Separately, the junction of C10 & R10 should connect to the base of TR3
(the bottom end of T3’s secondary), rather than the top of T3’s secondary.
Power LCR Meter, March & April 2025: in Fig.8 on p36 of the March issue, the
SI and SCK pins of IC5 are numbered incorrectly. SI is pin 6 and SCK is pin 5.
Mains Power-Up Sequencer, February, March & July 2024: if using the Mains
Detect Input feature, the 10μF electrolytic capacitor next to pin 4 of IC10
should be installed, even though it is in the Current Detection section. This
prevents false triggering due to EMI pickup.
Reciprocal Frequency Counter, July 2023: the lowest frequency the Counter
can measure is 2Hz, not 10mHz. Also, below 10Hz, its readings may not be
very accurate.
104
Silicon Chip
