108 Silicon chip Australia’s electronics magazine siliconchip.com.au
The LCD panel interface is using
both hardware chip select lines for
SPI(1) and the GP23, pin 16 needed
for SDIO CMD/MOSI is used to drive
the LCD reset line.
I have seen hardware and software
for SPI(1) and for SDIO to communi-
cate with a second SD card and hard-
ware for it to communicate with SPI(2)
but no high-level software to commu-
nicate with the SD card using SPI(2). I
hope you can help. (J. N., Woorim, Qld)- Your first challenge in using the
LCD’s SD card slot with the Raspberry
Pi display breakout board used in the
Tide Chart project is that it isn’t actu-
ally wired up. See the circuit diagram
on page 62 of the July 2018 issue. You
will have to make the required connec-
tions between the LCD module and the
Raspberry Pi somehow.
You could free up one of the hard-
ware CS pins of SPI(1) by changing
which pins are used to drive the LCD
DC/RESET lines. Once you’ve re-rout-
ed the tracks, you just need to change
our Python code to use the new pins.
We aren’t sure exactly what you are
trying to do, but if you just want to
store some additional data, the easiest
way to do that is to copy it onto the
same micro SD card that contains the
Raspberry Pi operating system. If you
use a large enough card, the OS will
only take up a tiny percentage and all
the rest can be used for general pur-
pose storage.
If you must have the data stored on
a separate SD card, an easier solution
might be to plug a USB card reader
into the Raspberry Pi. They only cost
a couple of dollars, are pretty fast, and
the files will be readily available in a
separate volume as soon as Linux de-
tects that the card has been plugged in.
Python code should have no trouble
accessing the files either.
Attaching ultrasonic
transducers to hull
I have built your Ultrasonic Anti-
Fouling unit (May & June 2017;
siliconchip.com.au/Series/312) and
am finally getting around to install-
ing it.
The instructions say to put silicone
grease between the hull and transduc-
er. Does this mean that we specifically
have to use silicone grease or can we
use any hydraulic fluid that doesn’t
leak out? (D.A.X., Netherlands)- Anything that helps make a void-
in a blue moon, would carbon zinc be
better to prevent battery leakage? (A.
R., Newport, Vic)- Alkaline cells have a very long shelf
life due to low current leakage, so these
are still the best choice for emergency
backup. These cells typically only start
to leak when completely discharged.
It is wise to check the cells on occa-
sion, both to ensure they still have ca-
pacity and to look for possible electro-
lyte leakage.
Carbon-zinc cells have a shorter
shelf life due to a higher internal leak-
age current and have a lower capac-
ity than alkaline cells. But they are
acceptable for low-drain use as long
as they are fresh. These cells can also
leak electrolyte when discharged, ei-
ther through self-discharge or power
drain when in use.
On balance, alkaline cells are almost
always the better choice.
Can battery desulfator
be used while charging?
Silicon chip is a great magazine. I
look forward to my copy every month.
I just finished building two of your
MPPT Solar Charger and Lighting
Controller units from the February &
March 2016 issues (siliconchip.com.
au/Series/296).
Can I use a battery desulfation unit
like the Lead-acid Battery Zapper
from July 2005 (siliconchip.com.au/
Article/3118) or a Megapulse MkII
unit in conjunction with the MPPT
Charger without doing damage to
the controller’s circuitry? (K.W., Bal-
logie, Qld)- You should not connect a battery
desulfation unit to the battery while
the MPPT Charger is connected, as
it could damage the driving Mosfets
in the MPPT Charger. Desulfation is
a process that you only need now
and then; it is better to disconnect
the charger while doing that, then re-
connected it after you have finished.
Accessing SD card from
Raspberry Pi Tide Clock
I have built the Raspberry Pi Tide
Chart (July 2018; siliconchip.com.au/
Article/11142), and it is working satis-
factorily. I want to activate the SD card
reader on the LCD but am snookered
whichever way I turn. There seem to
be two ways to talk to an SD card, SPI
or SDIO.ing sources.
These signals should be DC-biased
using the analog ground connection
provided at pin 5 of CON8.
We included both SPI and UART in-
terfaces on CON8 so that a wide range
of different potential audio sources
could be added to the radio.
The radio software would need to
be modified to switch the multiplexer
and send the appropriate control sig-
nals; the changes required are quite
straightforward.
Can’t get dimmer
remote control to work
I built John Clarke’s recent dim-
mer design (Versatile Trailing Edge
Dimmer, February-March 2019;
siliconchip.com.au/Series/332).
When using the touch plate, it works
well. However, I cannot get the remote
control to work. I have tried two re-
motes and replaced batteries in both
and also checked my soldering around
IRD1 many times!
The 47W resistor and 100μF elec-
tro feeding IRD1’s pin 3 have both
been checked for value and leakage
and found to be OK. I would appre-
ciate any help to resolve this. Thank
you in advance. (N. H., Sanctuary
Point, NSW)
- Please check that you are using the
SF-COM14865 remote control and
have the Murata IML0688 Fresnel lens
over the infrared receiver. Is the cell
inserted with the correct orientation
in the remote control?
Also, make sure there are no solder
bridges on the dimmer PCB that could
cause the output of the IR receiver (pin
- to be shorted out.
Alkaline vs carbon zinc
cell leakage
On page 110 of the February 2019
issue, you wrote that “Alkaline cells
are more prone to chemical leakage
than the earlier carbon-zinc types”.
I am now confused as to what bat-
tery type I should buy for emergency
backup devices like radios and torch-
es, that I keep in case of power failures
at home and in my car. I seldom use
these pieces of gear and could forget
to check the batteries.
So should I buy carbon-zinc batter-
ies for these applications? I only buy
the best quality alkaline cells for eve-
rything, but for items that I use once