92 Silicon chip Australia’s electronics magazine siliconchip.com.au
Alternatively, VR2 could have an in-
termittent wiper. The problem could
also be with the jack socket, CON2.
Make sure the pins make a connection
on both sides of the PCB. A problem
there can cause the loudspeaker con-
nection, via the switch contacts in the
socket, to be intermittent.
Modifying CLASSiC-D
for different transformer
I have built your CLASSiC-D Class-
D amplifier module from the Novem-
ber & December 2012 issues (www.
siliconchip.com.au/Series/17).
I am running it from a power sup-
ply which I built using a 30-0-30VAC
300VA toroidal torrid transformer.
This seems to power the CLASSiC-D
amplifier module OK, even though it
has ±42V rails rather than the speci-
fied ±50V.
Should I change any of the compo-
nent values to better suit the lower sup-
ply voltages? (B. C., Melbourne, Vic)
- As you have discovered, the am-
plifier will work OK with the compo-
nents designed for ±50V DC supply
rails, with your slightly lower ±42V
DC supply rails.
However, you could make the fol-
lowing component changes to opti-
mise its performance with your par-
ticular power supply:
Rf: 5.1kW; R2A, R2B, R3A, R3B:
3.9kW 1W; R4: 33kW; R5: 3.3kW; R6:
7.5kW, R7: 8.2kW, R8: 2kW, R9: 5.6kW,
R10: 470 W 1W; ZD5: 56V 1W; ZD6:
33V 1WDriveway Monitor not
always reliable at range
I recently built your latest Drive-
way Monitor (July and August 2015;
siliconchip.com.au/Series/288) using
the Altronics K4035 kit.
I am very impressed with its perfor-
mance. However, from time to time,
passing cars are not detected, and I
find the lack of any status indications
on either box quite frustrating.
When cars are missed, I first check
that the receiver has power, but if
that is OK, I have the 60m walk with
a screwdriver to get the lid off the de-
tector to check what I can there.
I can’t help thinking it would be of
great benefit to add a periodic status
transmission from the detector which
the receiver would pick up and blink
its green or red LEDs to indicate that
communications are either good or
bad.
It may also be possible to re-transmit
the last message in case it was missed
(but the receiver would need a way to
avoid sounding the alarm twice). Do
you think this could be a candidate fora future software update?
Since there is a hill in the middle of
the 60m distance from the entrance to
our driveway to our house, I have had
to drill holes in the boxes to extend the
antennas to a full wavelength.
Unfortunately, it’s difficult to orien-
tate the antennas of the two units in
the same plane. And despite the longer
antennas, I am still having this recep-
tion reliability problem.
In your Weatherduino Pro2 Wire-
less Weather Station project (March-
June 2015; siliconchip.com.au/Se-
ries/285), you used 433MHz antennas
purchased from eBay for the same fre-
quency. Would such antennas help me
achieve more consistent reception? (P.
B., Craignish, Qld)- It would be possible to send a peri-
odic transmission as a way of checking
that the RF link is working. We will
look into adding that to the software.
We’re planning to publish a solar-pow-
ered repeater design which you could
place at the top of your hill to solve
the line-of-sight problem.
Note that missed vehicles could be
the result of the vehicle being too far
from the Driveway Monitor. Make sure
that the detector is placed on a narrow
part of the driveway and as close to the
edge as possible.
Purpose-designed 433MHz anten-
nas probably would give better results
We intend to sail to New Zealand
later this month. Once there, I am
going to order a kit for your Ultra-
sonic Anti-Fouling MkII design (May
and June 2017; siliconchip.com.au/
Series/312) from Jaycar, including
the additional parts for a second
transducer.
I have a question concerning the
lengths of the transducer cables. Can
a transducer cable be shortened?
Based on reading the article, I have
already figured out where to locate
the transducers and the control box.
The cable run to the aft transducer
is likely to be less than two metres
(although I haven’t measured it ex-
actly yet).
Given that the transducer cable
carries AC, coiling the excess wire
is likely not an option. My question- can the cable be shortened? What
about replacing the plug?
Ultrasonic anti-fouling must have
a future role to play in reducing
the amount of toxins being leached
from our hulls into the marine en-
vironment.
But there are significant sub-
merged parts of a vessel that do not
benefit from the anti-fouling action
of the kit as sold – the drive train:
shaft/sail drive and propeller. These
parts are “insulated” from the hull
by rubber blocks and diaphragms.
Do you know whether the de-
signers of the current kit envisage a
low powered version, with a small-
er transducer? Such a transducer
could be bolted to an engine and/
or a sail drive. (D. P., Noumea, New
Caledonia)- The excess transducer wire length
is usually coiled up and tucked
away. The wire coiling does not af-
fect operation.
Ultrasonic Anti-Fouling lead length and protecting drive components
You can reduce the wire length
and reattach the end connector in-
stead but it’s extra work.
We haven’t produced a smaller
ultrasonic anti-fouling unit to cater
for unprotected parts of a boat such
as the propeller or rudder.
It has been found that the ultra-
sonic vibration of the boat hull does
protect these parts anyway, due to
the transmission of the ultrasonic
waves through the water.
Boats fitted with the Ultrasonic
Anti-Fouling unit do still need to be
occasionally hauled out of the wa-
ter for marine growth to be scraped
off but the intervals usually are
much longer than without it, and
the growth is not usually anywhere
near as bad.
You are right that this should lead
to a significant reduction in toxins
being released into seawater.