Altronics.................................77-80
Dave Thompson........................ 111
Digi-Key Electronics...................... 3
element14..................................... 7
Emona Instruments.................. IBC
Hare & Forbes............................... 9
Jaycar.............................. IFC,53-60
Keith Rippon Kit Assembly....... 111
Lazer Security........................... 111
LD Electronics........................... 111
LEDsales................................... 111
Microchip Technology.................. 5
Mouser Electronics..................OBC
Ocean Controls........................... 11
Silicon Chip Shop............ 106-107
The Loudspeaker Kit.com.......... 10
Tronixlabs.................................. 111
Wagner Electronics..................... 97
way to modify it to run by default
using 15.5 as the target ratio. Would
this require changing the wideband
sensor? (P. F., Willoughby, NSW)
● The sensor actually measures the
lambda value, and the air/fuel ratio
is calculated from that.
That means the same sensor and
controller will work fine regardless of
whether you are using petrol or LPG. It
will show a lambda of 1.0 if the mixture is stoichiometric, irrespective
of the actual air:fuel ratio of the fuel
being burned.
Oxygen sensors measure whether
the exhaust has excess oxygen (lean)
or no oxygen and unburnt fuel (rich)
or completely burnt fuel with no oxygen leftover (stoichiometric). The sensor does not actually measure the air/
fuel ratio directly.
If you want to display the air/fuel
ratio rather than the lambda value, the
unit needs to know the stoichiometric ratio for the fuel you are currently
using. The problem is that the fuel type
could change.
Since you usually use LPG, you
could just set that to 15.5:1 and realise that the readings displayed when
running on petrol will be 5.5% too
high. But the engine won’t care since
112
Silicon Chip
Running appliances
from higher voltages
I would like to request assistance
regarding a Panasonic hair dryer made
in Japan. It is labelled as 100V 1200W.
Can I run this from 110V AC? I can plug
it into a 110V outlet, but in the long
run, the motor will fail. Could I use a
Triac-based circuit? Thank you very
much. (D. H., Taipei, Taiwan)
● One method is to use a transformer
to reduce the mains voltage, as in our
Mains Moderator project (March 2011;
siliconchip.com.au/Article/937). The
secondary windings are wired in series
with the primary but out-of-phase.
The result is that the secondary voltage is subtracted from the original
mains voltage before being applied
to the load.
That circuit was designed for the
Australian mains voltage, nominally
230V AC. But the same applies to your
110V supply if you use a suitably-rated
transformer with a 10V or 12V tapping to reduce the mains voltage by
that amount.
Note that the 1200W hair dryer
draws up to 12A (assuming most of the
load is the resistive heater element),
so the transformer would need to have
a secondary current rating of at least
12A. That’s a large transformer.
An alternative is to use two strings
of around 10 diodes, one set for either
mains polarity, to drop the 10V. But
the diodes would need to be rated for
12A and preferably 20A, meaning they
would need to be substantial devices.
Either circuit would need to be
installed in a suitable Earthed enclosure with the correct input and output
plugs and sockets. The diodes would
need heatsinking to the case and isolated electrically.
You could use a phase controller
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it’s using the lambda value.
Note that the air/fuel ratio also varies depending on the fuel grade. So it’s
better just to show the lambda value
as it will always be correct.
with a Triac. We don’t have a circuit
that would work at 110V AC, as our
designs are for 230V AC and wouldn’t
be powered sufficiently. Also, most of
our designs are rated for 10A rather
than the 12A required for the hair
dryer. Also note that the Triac would
reduce the RMS voltage, but the peak
of the 110V waveform would still be
applied to the motor.
If you can get a 110V AC rated
Triac-based dimmer that can handle 12A or more, you could use that.
But we think you might find it easier
(and possibly cheaper) to purchase a
110V-rated hair dryer.
Is Playmaster 136 up to
modern standards?
I would like to know if the Playmaster 136 preamp could be used in
an Ultra Low Distortion Amplifier,
primarily because I’m running out of
funds and would like to still be able
to use my record player. (M. G. M.,
Trott Park, SA)
● The Playmaster 136 is from the
1970s era and has a poor signal-tonoise ratio and high distortion compared to anything we have published
recently. You could use it, but it
wouldn’t be doing the amplifier justice.
Given your limited budget, consider
building the Ultra Low Noise Remote
Controlled Stereo Preamp (March &
April 2019; siliconchip.au/Series/333)
without the input switcher and using
a standard 16mm potentiometer in
place of the motorised pot. You can
then omit the microcontroller, 5V
regulator and all components in that
section. You could still use our PCB.
That would give you a preamp
with excellent performance that you
could probably build for around $40
(depending on where you get the parts,
which exact parts you use etc).
It doesn’t have a built-in RIAA preamp but you can get an external RIAA
premap for your turntable from Jaycar
for $21.95 (Cat AC1649).
SC
500W Power Amplifier pt2, May 2022: inductor L1 is wound using 13.5
turns of 1.25mm diameter wire, not 30.5 turns of 1mm diameter as stated
in two places on p64 & p65. Around 900mm of wire will be consumed.
Model Railway Semaphore Signal, April 2022: trimpots VR1 & VR2 are
1kW, not 10kW as shown in Fig.8 on p56.
Next Issue: the July 2022 issue is due on sale in newsagents by Monday,
June 27th. Expect postal delivery of subscription copies in Australia
between June 27th and July 11th.
Australia's electronics magazine
siliconchip.com.au
