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•
Unfortunately, the maximum rate
is determined by the TFDS4500
module, which you correctly state at
115.2kbps.
We may publish something faster
in the future (MIR and/or FIR) but we
can’t give any guarantees. If you’re
keen to upgrade soon, you might consider a commercial solution.
Microgram Computers often advertise IR add-ons – check them out at
www.mgram.com.au
Ammeter has
stopped working
I recently constructed the 80A Automotive Ammeter from the June 2002
issue and it was working well. However, it now fails to give any correct
indication of current levels.
When I attempted to re-calibrate
the unit at the ‘zero’ current level, the
‘CAL’ LEDs light but on removal of the
shorting plug, the indication goes to
‘OL’. Attempts to calibrate at other
levels bring either totally erroneous
(high) readings or the ‘OL’ indication
again.
The ammeter is an important part
of my domestic solar system. I gather
it should work satisfactorily in this
situation? (R. T., Darbys Falls, NSW).
• Perhaps there is a short in the Hall
effect wiring or the Hall sensor is not
working. Check that the Hall effect unit
is receiving its 5V supply and that its
output is around 2.5V.
Alternatively, there may be a problem with the LM358 and associated
components. Check its supply and
that the output is a varying voltage,
indicating that the conversion process
is working.
Operating the turbo
timer from 24V
Is it possible to operate the turbo
timer (SILICON CHIP, November 1998)
on 24V DC. If so, what mods do I need
to make? (G. S., via email).
• It is possible to operate the turbo
timer from 24V. Change the 33Ω resis-
tor to ZD1 to a 680Ω 1 W resistor and
change ZD1 to a 15V 1 W zener. Also,
change the 10kΩ resistor connecting
between ground and the 1.8kΩ resistor
to 1kΩ.
Also the relays will need a series
resistor with the 12V relay coil to limit
the voltage across their coils. Measure
the coil resistance in ohms and use a
5W resistor of the same value in series
SC
with the coils.
Notes & Errata
Whistle & Point Cable Tracer, October 2002: the pinout diagram for
the C8050 package (circuit, page 54)
is incorrect. The C8050 collector
& emitter pins are reversed with
respect to common general-purpose
TO-92 transistors like the BC549.
5A Speed Control, October 2002:
the 100nF capacitor shown on the
PC board diagram on page 17 should
be 47nF to agree with the circuit on
the same page.
Note also that the pinout diagram
for the MCR100 on the circuit is
wrong with regard to the Anode
and Gate pins. The gate is the centre
pin of the package as it is with the
C103B however the A and K pins
are swapped.
40W Fluorescent Inverter, September 2002: due to tolerance variations
within the L6574 (IC3), it is recommended that the maximum current
delivered to the fluorescent tube be
adjusted using a trimpot. The 100kΩ
resistor connecting between pin 2
of IC3 and the top of the dimming
potentiometer (VR1) should be
replaced with a 50kΩ trimpot and
www.siliconchip.com.au
series 82kΩ resistor. The 1.2Ω resistor between the source of Q4 and
ground should be changed to 2.2Ω
to allow the full dimming range
available from VR1.
Using the current measuring setup of Fig.8, the trimpot should be
adjusted for the 370mV, corresponding to 3.7A when the dimming pot
(VR1) is turned fully clockwise.
Note that this adjustment should
be made after the inverter has been
running for some time and is fully
warmed up. Once adjusted, the
trimpot and 82kΩ resistor can be
swapped for a single resistor that
is the same value as the total series
combination.
When testing the current (using
the setup of Fig.8), it is important
not to have the 0.1Ω 5W resistor in
series with the supply for any appreciable length of time as the current drawn will begin to increase.
To prevent this, short out the 0.1Ω
resistor (with a clip lead) when not
making the measurement. Remove
the clip lead briefly to make the
current measurement.
In addition, use heavy gauge wire
rated at 7.5A or more to connect the
inverter to the 12V battery.
The lower cost MTP3055E Mos
fets can be substituted for the
STP60NE06 devices used for Q1
and Q2.
The Dick Smith Electronics
D-5375 ferrite core is also suitable
for L2 and requires 100 turns of wire
(50 turns on each half) instead of the
84 total shown in Fig.6.
4-Channel UHF Remote Control,
July 2002: the circuit diagram on
page 20 is incorrect. On the PC
board overlay diagram, the col
lectors of all four transistors (Q1Q4) connect first to 2.2kΩ resistors,
then to their respective LEDs.
However, the resistors and LEDs
are swapped on the circuit diagram.
MP3 Jukebox, September/October
2001: since publication of this
project, version 2 of the Winamp
software has been superseded by
version 3. Unfortunately, Winamp
version 3 is not suitable for use with
the MP3 Jukebox. However, the last
release of version 2 (v2.8.1) can be
downloaded from http://classic.
SC
winamp.com
December 2002 93
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