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The photo below shows how the small IR-ToUHF Converter board fits inside a universal
remote control while at right is the companion
UHF-To-IR Converter.
By JOHN CLARKE
Add a UHF link to a
universal remote control
Remote control extenders are old hat. Now you can add this tiny
UHF module to your IR remote control and operate appliances
from anywhere inside or outside your home. As well as the tiny
module inside the remote, you also need our UHF-To-Infrared
Converter which is positioned close to the device to be controlled.
O
VER THE YEARS, we have produced several infrared remote
control extenders, the most recent
being in October 2006. That project
essentially received the IR signal from
any remote control and the signal was
then retransmitted using an IR LED
that was attached to a long lead. This
could be placed closer to the appliance
being controlled (eg, in another room).
More recently, there have been
UHF remote control extenders. These
receive the pulsed IR signal from the
remote control and then re-radiate it at
2.4GHz. You then have a UHF receiver
elsewhere in your home which picks
up the 2.4GHz signal and converts it
back to infrared pulses to be received
by the appliance being controlled.
Both approaches make sense but
why not have a remote control that
64 Silicon Chip
works at both infrared and UHF, rather
than having a separate transmitter
unit? So that is what this project is
about. You build a tiny UHF module
into the remote control and power it
from the remote’s AA cells; there’s no
external remote transmitter and power
supply to worry about.
Of course, you still need a UHF
receiver/IR converter at the appliance
end and that’s also described here.
This approach is so much more
convenient than past remote control
extenders. For example, say you are
out on the balcony having a pleasant
lunch and the CD player is inside
providing background music. Want to
change a track and change the volume?
No need to wander back inside, find
the remote and then wander out again.
You just pick up the same hand-held
remote that you use inside and use it
where you are.
Both the UHF and infrared signals
are radiated simultaneously, so it does
not matter whether you are inside your
home or outdoors.
Sound like a good idea? We thought
so too and this project is the result.
We have designed a small PCB module that fits inside the remote control
case. You will need to check that it
will fit inside the remote control that
you want to convert. Some remote
controls will be too small or have very
little room inside the case but many
do have enough room, particularly
universal remotes.
What about current drain?
But what about the extra current that
will be drawn by the UHF module?
siliconchip.com.au
+3V
+
K
TO 3V
BATTERY
IN REMOTE
1 F
D1
1N4004
1k
MMC
4
A
–
1
Vdd
MCLR/GP3
GP5
100
X
1
OPTO1 4N25
2
Y
6
ANTENNA
2
1 F
3
IC1
GP4
PIC12F6756
I/P
GP1
47k
5
7
GP0
4
GP2
MMC
TX1
433MHz
TX
MODULE
DATA
5
Vss
1k
Vcc
8
ANT
GND
4N25
433MHz Tx MODULE
SC
2013
1N4004
IR-TO-UHF CONVERTER
A
K
ANT
Vcc
DATA
GND
3
6
1
Fig.1: the IR-To-UHF Converter circuit. The IR LED driver circuit in the remote feeds the 38kHz signal in via OPTO1 and
this drives pin 7 of PIC microcontroller IC1. The micro then powers and drives the 433MHz transmitter module (TX1).
Will it drain the cells by too much and
greatly reduce their life? No-one likes
having to continually replace batteries
in remote controls.
For this reason, we have been very
careful with this aspect and the current
drain is truly negligible. Typically, it
will be just a few nanoamps although
we measured one of our prototypes at
just 200 picoamps! That’s much less
than one thousandth of a microamp!
Compare that with the typical microamp or so drawn by a remote control
from its AA or AAA cells. Naturally,
more current is drawn from the battery
when transmitting both the IR and
UHF pulsed signal but it still does not
amount to much. In a typical universal remote, the average current while
transmitting increases from 10mA with
IR transmission alone to 12mA with
both IR and UHF transmission – an
increase of just 2mA.
Since remote controls only draw
significant current while buttons are
being pressed, the overall extra current
drain with UHF transmission added
+3V
is unimportant. The AA or AAA cells
will still last their shelf life (years).
The companion UHF-To-IR Convert
er is housed in a small plastic case.
At one end of the case it has a red
acknowledge LED as well as an IR
LED to retransmit the received UHF
signal as an IR signal. As well, there
is a 3.5mm socket to allow connection
of an external IR LED (ie, via a cable).
The converter runs from a 9-12V DC
plugpack and it draws a maximum of
50mA when transmitting, so any 9-12V
DC plugpack will be suitable.
Circuit details
Fig.1 shows the circuit of the IRTo-UHF Converter to be built into the
remote control. It uses an optocoupler
(OPTO1), a PIC12F675 microcontroller (IC1) and a tiny UHF transmitter
module (TX1) which runs at 433MHz.
As stated, it’s powered from the remote’s two AA (or AAA) cells (ie, 3V).
The optocoupler is needed to allow for any of the possible LED drive
arrangements and provides isolation
+3V
X
A
(b)
K
Y
X
X
A
2.7
(TYP.)
(a)
from the rest of the circuit. The various
possibilities are shown in Fig.2. The
input of the optocoupler connects, via
a 100Ω resistor, across the IR LED drive
circuit on the remote control’s PCB.
For example, in the Altronics
A-1012 universal remote, the IR LED
drive is as depicted in Fig.2(a). In this
case, the “X” terminal input to the
optocoupler connects to the +3V supply rail and the “Y” terminal connects
to the cathode of the IR LED.
For arrangements such as Fig.2(b),
the +3V positive rail is easily accessible but the LED driver output needs to
be picked off the series resistor itself.
You may need to lift out the remote’s
PCB to access this resistor.
The optocoupler’s internal transistor is connected as an emitter follower,
with its base tied to the emitter with a
47kΩ resistor to speed up switching.
The resistor effectively discharges the
transistor’s base each time the opto’s
internal IR diode stops emitting (ie,
at the end of each pulse in the 38kHz
signal burst). This allows the transis-
X
A
K
(c)
2.7
(TYP.)
Y
2.7
(TYP.)
(d)
K
2.7
(TYP.)
A
K
Y
Y
Fig.2: the four possible IR LED driver arrangements in a remote control. The signal drive to the IR-To-UHF Converter
must be taken from the points labelled “X” and “Y” (see text for determining the configuration of your remote).
siliconchip.com.au
July 2013 65
OUT
ANTENNA
1k
ANT
Vcc
433MHz
RX
MODULE
GND
4
DATA
2
CARRIER
ADJUST
VR1
10k
433MHz Rx MODULE
MIN
MCLR/GP3
1
Vdd
GP0
GP5
GP4
GP2
100 F
16V
A
220
A
(ACK)
LED2
K
220
5
Vss
8
MAX
9–12V
DC IN
1k
7
IC1
6
PIC12F675- GP1
I/P
3
CON1
A
K
IN
GND
100 F
16V
100nF
RX1
D1 1N4004
REG1 78L05
+5V
CON2
EXTERNAL
IR LED
(IR LED)
LED1
SC
2013
Vcc
DATA
DATA
GND
ANT
GND
GND
Vcc
K
LEDS
UHF-TO-IR CONVERTER
1N4004
A
K
K
A
78L05
GND
IN
OUT
Fig.3: the UHF-To-IR Converter circuit picks up the transmitted 433MHz signal using RX1 and feeds it to PIC
microcontroller IC1. IC1 in turn drives an infrared LED (LED1) and an acknowledge LED (LED2).
tor to switch off faster than if its base
were left floating.
The opto’s emitter signal is applied
to the GP0 input (pin 7) of microcontroller IC1. With no 38kHz signal burst
present at pin 7, IC2 is in sleep mode.
Its GP1, GP2, GP4 & GP5 outputs are
all low, so transmitter TX1 is off and
the circuit draws minimal power at
around 12nA.
At the onset of signal at pin 7, IC1
wakes up and sets its GP1, GP4 &
GP5 outputs high (3V) to power up
the UHF transmitter (TX1). IC1 also
demodulates the 38kHz signal, so
that the output at pin 5 is identical to
the original modulation on the 38kHz
bursts.
TX1 transmits the UHF signal using a 170mm antenna which is just a
length of hook-up wire. After a period
of 600ms with no 38kHz signal, power
to TX1 is removed with GP1, GP4 &
GP5 going low.
Using a microcontroller might seem
like overkill for the circuit. However,
it was chosen simply because it can be
put to sleep and thereby draw negligible current from the remote control’s
cells. Any other approach, such as using a couple of CMOS timers (eg, 7555),
would have much higher current drain
than the remote control itself.
UHF-To-IR Converter
The modulated UHF signal needs
to be detected and converted back to
a stream of infrared pulses to control
the appliance being operated. For
that we need the separate UHF-To-IR
Converter referred to above.
The converter circuit is shown in
Fig.3 and comprises UHF receiver
RX1, another PIC12F675 microcontroller (IC1) and an IR LED (LED1).
The whole circuit is powered from
9-12V DC.
The UHF receiver is powered continuously, so that it is ready to receive a
transmission from the IR-To-UHF Con-
Measuring The Standby Current
How do we measure a standby current of only 12nA? After all, this is far below
the current ranges of any digital multimeter.
The procedure is to feed the supply to the circuit via a 100kΩ resistor but with a
switch connected across it to allow the circuit to be powered up normally; it does
draw more current at power up. Then, after a second or so when the micro has
gone to sleep, the switch is opened and the voltage across the resistor is measured.
For 12nA, the voltage measured across the 100kΩ resistor is 1.2mV.
66 Silicon Chip
verter in the hand-held remote. With
no signal present, the data output from
the UHF receiver is just random noise
with an amplitude of 5V. In this state,
the receiver operates at maximum gain,
due to its automatic gain control (AGC).
When a UHF signal is received, the
AGC reduces the receiver’s sensitivity
so that the detected signal is essentially noise-free. This is fed to the GP5
input (pin 2) of PIC micro IC1.
To determine if a signal is valid,
IC1 checks for periods where the data
line from the UHF receiver is at 0V for
at least 8ms. This indicates that the
AGC has reduced the sensitivity of
the receiver and that a transmission
is occurring. The 8ms periods also
indicate breaks between successive
bursts of 433MHz signal.
IC1 drives the IR LED (LED1) and
siliconchip.com.au
This view shows how the IR-To-UHF Converter board is mounted and wired
inside the Altronics A-1012 universal infrared remote control. The PCB
assembly should also fit inside many other universal remotes.
0V
+3V
4004
D1
13170151
IC1
OPTO1
4N25
1k
47k
PIC12F675
ANT
K
433MHz Tx
MODULE
100
A
C 2013
TX1
1k
1 F
IR to UHF
CONVERTER
+ 1 F
–
X
Y
TO IR LED
DRIVER CIRCUIT
IN REMOTE
ANTENNA:
170mm LONG
an Acknowledge LED (LED2) from
its GP1, GP2 & GP0 outputs; ie, GP0
drives LED2, while GP1 & GP2 drive
LED1. Note that the acknowledge LED
does not simply follow the data signal
level; it is only intended as a visible
confirmation that a valid signal is being received.
A second output is provided via a
3.5mm jack socket (CON2) for an external IR LED (if necessary). This LED can
be wired to a 3.5mm jack plug on the end
of a cable to allow the LED to be attached
or mounted near to the IR receiver of the
appliance(s) being operated.
The GP4 input of IC1 monitors the
voltage set by trimpot VR1 which is
across the 5V supply rail. Its wiper
voltage is converted to a digital value
within IC1, allowing the IR carrier
frequency to be adjusted to suit the
particular infrared receiver in the
appliance under IR control. The adjustment range is from 33.33kHz to
47.66kHz in 10 steps.
Setting VR1 to its mid position gives
38kHz. Usually, 38kHz is satisfactory
but some remotes may require a different carrier frequency to this.
siliconchip.com.au
Fig.4: follow this parts
layout diagram to
build the IR-To-UHF
Converter. Power
comes from the
remote’s 3V supply,
while the input to
OPTO1 comes from the
remote’s IR LED driver
circuit (see Fig.2).
Main Features & Specifications
IR-To-UHF Converter
Transmission range to UHF receiver: >30m
Signal detect delay: 62μs for start and finish
UHF transmitter power down: 600ms from end of signal
Standby current: 12nA typical (12nA measured on prototype)
Operating current: unmodified IR hand-held remote = 10mA; with UHF transmission = 12mA total
UHF-To-IR Converter
Valid transmission: requires 8ms minimum quieting period
Acknowledge LED: 654ms time-out after a valid signal
Modulation frequency adjustment: 33.33-47.66kHz in 10 steps
Current consumption: 50mA during reception and transmission of an IR signal
IR transmission range: typically 2m to appliance receiver
Power is derived from a 9-12V DC
plugpack. This is fed in via diode D1
which provides reverse polarity protection. A 78L05 3-terminal regulator
then provides a 5V supply for RX1
and IC1.
IR-To-UHF converter assembly
Refer now to Fig.4 for the assembly
details on the IR-To-UHF Converter.
July 2013 67
23170151
100 F
78L05
100 F
IC1
A
A
220
220
Vcc
DATA
DATA
GND
VR1
10k
15107132
1k
PIC12F675
1k
ANT
GND
GND
Vcc
DC IN
LED2
ACK.
100nF
CON1
CARRIER
FREQUENCY
D1
4004
REG1
LED1
CON2
RX1
C 2013
UHF RECEIVER
toT IR
DEL RI O
r evLED
i e c eR F HU
ANTENNA: 170mm LONG
Fig.5: this parts layout diagram and the accompanying photo show the assembly details for the UHF-To-IR Converter.
Trimpot VR1 sets the output IR carrier frequency and should initially set mid-way to give a frequency close to 38kHz.
It’s built on a PCB coded 15107131
and measuring just 20 x 47mm.
Begin by checking the PCB for any
faults (rare), then start the assembly
by installing the resistors and diode
D1. Table 1 shows the resistor colour
codes but you should also check each
one using a digital multimeter. Make
sure the diode is installed with the
correct polarity.
The two capacitors go in next, followed by IC1 and optocoupler OPTO1.
Both IC1 & OPTO1 are soldered directly on the PCB since there is insufficient space in the remote control case
to allow sockets to be used.
Follow with the 433MHz UHF transmitter (TX1). This is installed parallel
to the PCB, so its leads have to be bent
down by 90° before soldering it in
place. It should be stood off the PCB
slightly so that it is about same height
above the PCB as the ICs. Once it’s in,
install the 170mm-long antenna wire.
Installation
The first step in the installation is
to open the remote control case. For
the Altronics A-1012, a screw within
the battery compartment must first be
removed, after which the two halves of
the case can be carefully prised apart
using a wide blade.
It’s then just a matter of installing
the power supply leads and the leads
that run from the remote’s IR driver
circuitry to the optocoupler. Note that
the supply leads must be run around
the edge of the case, so that they
don’t foul other parts when the case
Fig.6: these waveforms show the operation of the IR-To-UHF
Converter installed in the remote control. The yellow trace
shows the bursts of 38kHz applied to the IR LED. These are
coupled via the optocoupler to the microcontroller which
then sends pulses of the same length to turn on the 433MHz
transmitter (green trace). Scope timebase speed is 500μs/div.
68 Silicon Chip
is closed. If necessary, notches can be
cut into any internal plastic ribs and
the wires pressed into these notches.
Make sure that the supply leads
connect across the full 3V supply (and
not just across one cell) and be sure to
connect them the right way around.
As shown in Fig.2, the IR LED can
be driven in several different ways,
depending on the remote control. This
will determine how the “X” & “Y” connections from the converter are wired
to the remote’s IR driver circuitry.
Fig.2(a) and the photos show the
connection for the Altronics A-1012
remote. You can determine how the
IR LED is connected in your particular
remote using a multimeter (DMM).
First, set the DMM to a low ohms
range, then short its leads together and
Fig.7: these are the same signals as in Fig.6 but at a timebase speed 10 times slower, at 5ms/div, to show the entire
data block being transmitted. Note that there is a delay of
about 50μs between the 38kHz bursts and the equivalent
pulse fed to the transmitter. This is processing delay in the
microcontroller.
siliconchip.com.au
The completed
board assembly
clips into the
integral side ribs
in the UB5 plastic
case. Note how the
IR LED (LED1) is
bent across the top
of the 3.5mm jack
socket.
check that it shows a 0Ω reading. Clean
the multimeter contacts if the reading
is above 0.5Ω. Now, with the two cells
removed from the remote, measure the
resistance between the anode of its IR
LED and the positive battery terminal.
The readings are interpreted as
follows:
(1) a reading of about 2-3Ω means that
circuit is as shown in Fig.2(a) – ie, the
limiting resistor is in series between
the supply and the IR LED;
(2) a 0Ω reading between the anode and
the positive terminal means a direct
connection like that shown in Fig.2(b).
If you get a high resistance reading, check the resistance between the
cathode of the IR LED and the negative
battery terminal. In this case, the readings indicate the following:
(3) a reading of about 2-3Ω means that
circuit is as shown in Fig.2(c)
(4) a 0Ω reading indicates the arrangement shown in Fig.2(d).
Once you’ve determined the configuration, it’s simply a matter of tracing
the connection from the IR LED to its
limiting resistor and then running the
leads back to the “X” & “Y” connections on the converter PCB. In practice,
this means that you have to take the
drive from across the IR LED and its
series limiting resistor. Be sure to get
the connections to the remote’s drive
circuit the right way around, otherwise
the converter won’t work.
UHF-To-IR Converter assembly
The companion UHF-To-IR Converter is built on a PCB coded 15107132
Fig.8: these waveforms demonstrate the reception and
conversion of the remote control’s 38kHz infrared pulses.
The yellow trace shows the remote’s 38kHz signal, the
green trace is the Acknowledge LED signal and the blue
trace shows the infrared pulses emitted from the UHF-ToInfrared Converter. The scope timebase speed it 500μs/div.
siliconchip.com.au
and measuring 79 x 47mm. This clips
neatly into a UB5 plastic utility box
measuring 83 x 54 x 31mm and a frontpanel label (78 x 49mm) is affixed to
the lid.
Fig.5 shows the parts layout on the
PCB. Install the resistors and diode
D1 first, taking care to ensure that the
latter is correctly orientated. The capacitors can then be fitted; make sure
that the two 100µF electrolytics go in
with the correct polarity.
REG1 can then be mounted, followed by the DC socket (CON1), the
3.5mm jack socket (CON2) and trimpot
VR1 (set it mid-way). That done, install
the UHF receiver (RX1), making sure
it goes in the right way around.
Installing the LEDs
Now for the two LEDs. LED1 must
be mounted at full lead length (25mm)
so that it can be later bent over and its
lens pushed through a hole in the side
of the box (above the 3.5mm socket).
LED2 is mounted with the top of its
lens 20mm above the PCB surface.
That’s done by pushing it down onto
a 15mm cardboard spacer inserted
between its leads before soldering it to
the PCB. Make sure the LED is orientated correctly, with its anode (longer)
lead going to the pad marked “A”.
Finally, complete the PCB assembly
by fitting a 170mm-long antenna wire.
The PCB assembly can now be completed by installing an 8-pin DIL socket
for IC1 but do not plug the PIC micro
in at this stage. That step comes later,
Fig.9: these waveforms are the same signals as in Fig.8 but
with a timebase speed 10 times faster to show more detail.
Note the rounding of the trailing edges of the transmitted
38kHz IR pulses (yellow trace) from the remote control
but the much cleaner signal being re-transmitted from the
UHF-To-Infrared Converter (blue trace).
July 2013 69
Modifying The 10-Channel
Remote Control Receiver
Simple changes let you install the IR receiver & the 433MHz UHF
receiver at the same time for use with both IR & UHF remotes
As good as it is, last month’s 10-Channel Remote Control Receiver can be
even more useful when teamed with an IR remote control that’s fitted with
the tiny IR-To-UHF Converter. A couple of modifications to the PCB and
some revised software for the microcontroller now allows it to be used
with both IR & UHF remote control signals.
By JOHN CLARKE
With the tiny UHF module installed in a remote, you can control
the modified 10-Channel Remote
Control Receiver via both IR and
UHF signals. When the remote control is within line of sight, the the
receiver works by relying on IR signals. However, if you are in another
room or outside your home, then the
link is via UHF and the operation
is seamless; there’s no need to do
anything to change modes.
Alternatively, you could have
two remotes to control the 10-Channel Remote Control Receiver, one
unmodified and one with the UHF
module installed. For example,
the receiver unit could be in your
workshop or garage (to operate the
doors perhaps) and you could have
the option of controlling it using an
unmodified IR unit located nearby or
via a modified unit with UHF from
inside the house.
The circuit changes required to
make this possible are quite simple.
The original circuit has both the IR
signal from IRD1 and the UHF signal
from RX1 being applied to the RB3
input of IC1. In practice, this meant
that you had to choose between installing either the infrared receiver
(IRD1) or the UHF receiver (RX1)
and install or remove the SET link
accordingly.
By contrast, the revised circuit
allows both IRD1 and RX1 to be installed and the micro automatically
selects between them. Fig.10 shows
the circuit details. As can be seen,
IRD1’s signal is applied to the RB3
input, while RX1’s signal is now
applied to the RB2 (SET) input. The
microcontroller separately checks
for signals from either path and
chooses the first valid signal.
after the power supply has been tested.
At the other end of the case, the
3.5mm socket hole is also centred
horizontally and is positioned 10.5mm
down from the lip. Again, use a pilot drill to start it, then enlarge it to
6.5mm.
The hole for LED1 is then drilled
3.5mm down from the lip directly
above the socket hole. Drill this hole
to 3mm, then drill a similar hole for
LED2 about 12mm to the right.
The PCB can now be clipped into
the slots in the side ribs of the box
(push the 3.5mm jack socket into its
hole first). Once it’s in place, the two
LEDs are then bent over and pushed
through their respective holes in the
adjacent end. Secure the assembly by
fitting the nut to the jack socket.
Finally, the front-panel label can be
downloaded (in PDF format) from www.
siliconchip.com.au (go to “Shop” and
then “Panel artwork”), printed out on
photo paper and affixed to the lid using
silicone or some other suitable adhesive.
The four corner holes for the case screws
are cut out using a sharp hobby knife.
Note: the panel artwork is free to
subscribers or if you purchase the PCB
from the SILICON CHIP Online shop,
Final assembly
The PCB simply clips into the integral ribs of the UB5 case. Before doing
this, you need to drill holes in the case
ends for the DC socket, the 3.5mm
socket and the two LEDs.
The DC socket hole can be drilled
first. This is positioned 6.5mm down
from the top lip of the base at the lefthand end and is centred horizontally.
Start this hole using a small pilot drill
to begin with, then carefully enlarge
it to 6.5mm using a tapered reamer.
70 Silicon Chip
Modifying the PCB
To modify the original PCB (coded
15106131), first cut the track that
leads from the DATA output of the
UHF receiver (RX1) at the point
where it connects to the track that
runs from IRD1’s pin 1 output to
pin 9 of IC1. Note that this track is
on the top side of the PCB. Do not
break the connection from pin 1 of
IRD1 to pin 9 of IC1.
That done, solder an insulated
wire link under the PCB between
the DATA output of RX1 and pin 8 of
IC1. The SET jumper must be left out.
Both IRD1 and RX1 need to be installed on the PCB for both reception
modes to be available. If you only
install one of these, the unused input
siliconchip.com.au
100
at pin 8 or pin 9 must be tied to ground. So, if IRD1 is
out of circuit, bridge pins 1 & 2 of IRD1’s pads. If RX1
is out of circuit, install the SET jumper.
100 F
16V
IRD1
IR
RECEIVER
10k
Modified PCB
9
RB1
RB3
IR
SHUNT
2
RB0
RA4
OPEN = IRD1 installed
CLOSED = IRD1 out
RX1
ANT
RA3
Vcc
433MHz
RX
MODULE
3
2
Revised software
Vdd
MCLR
1
A modified PCB, code 15106133, is also available that
includes the necessary track modifications.
Fig.11 shows the parts layout for this PCB. If both IRD1
and RX1 are installed, then both the IR SHUNT and UHF
SHUNT jumpers are left out. If either IRD1 or RX1 is left
out, then its associated shunt jumper must be installed.
14
4
3
7
6
The revised software for the microcontroller is coded
1510613B. It must be used regardless as to whether you
modify the original PCB or use the revised PCB design.
Note: this software is not suitable for use with the original
unmodified PCB.
The new software is available for download from
the SILICON CHIP website, while the revised PCB can be
purchased from the SILICON CHIP Online shop at www.
siliconchip.com.au The software is free to subscribers or
if you purchase the PCB, otherwise a small fee applies.
1
RA2
IC1
PIC16F88
18
-I/P
RA1
DATA
8
GND
11
OPEN = RX1installed
CLOSED = RX1 out
10
UHF
SHUNT
12
RB2
RA0
RB5
RA7
RB4
RA6
RB6
RB7
17
16
15
13
Vss
5
Fig.11 (below): the parts layout for the modified PCB. Be
sure to install the relevant SHUNT jumper if its receiver is
left out of circuit (see text).
CODE 2
315106133
3160151
C 2013
+ OUT0
+ OUT4
0V
+OUT9
433MHz Rx MODULE
100
1k
RX1
2
1k
1
1k
CODE
1k
1k
Shunt when
Receiver is
off PCB
SHUNT
UHF
1k
1k
1k
1k
100 F
100 F
100nF
IR
LED10
+ OUT8
IC3 ULN2003
1k
IC2 ULN2003
+12V
+ OUT7
100nF
D1
K
+ OUT6
100 F
A
ACK
+ OUT5
1k
1k
REG1
7805
+ OUT3
GND
DATA
DATA
Vcc
CON1
Fig.10 (above): the revised
front-end circuit for the
10-Channel Remote Control
Receiver. The outputs from
IRD1 & RX1 are now fed to
separate inputs in IC1 and
the micro automatically
selects between them.
CON2
+ OUT2
10k
& CODE2 OUT = TV
IN, CODE2 OUT = SAT1
OUT, CODE2 IN = SAT2
& CODE2 IN = CD PLAYER
4004
CODE1
CODE1
CODE1
CODE1
+ OUT1
10-CHANNEL
REVIE CEREMOTE
R ET O MERECEIVER
R LE N NA H C- 0 1
IC1 PIC16F88-I/P
CODE 1
ACK.
ANT.
Vcc
GND
GND
ANT
A
LED0
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
LED9
LED10
IRD1
Table 1: Resistor Colour Codes
o
o
o
o
o
No.
1
4
2
1
Value
47kΩ
1kΩ
220Ω
100Ω
otherwise a small fee applies.
Testing
To test the unit, first check that IC1
has not been installed. That done,
apply power and check there is 5V
between pins 1 & 8 of the IC socket. If
siliconchip.com.au
4-Band Code (1%)
yellow violet orange brown
brown black red brown
red red brown brown
brown black brown brown
not, check the supply polarity and that
D1 and REG1 are correctly orientated.
Assuming you do get 5V, switch off
and install IC1 with its notched end
towards the adjacent 100nF capacitor.
Now reapply power and check that the
red acknowledge LED flashes when the
5-Band Code (1%)
yellow violet black red brown
brown black black brown brown
red red black black brown
brown black black black brown
remote control buttons are pressed.
Note, if it does not work the 100Ω
resistor to the opto-coupler may need
to be switched out; try 47Ω or if that
doesn’t work, you can go as low as 22Ω.
The next step is to set the universal
remote control so that it produces the
July 2013 71
INNER CONDUCTOR
SOLDERED TO TIP
3.5mm MONO PLUG
SHIELD BRAID SOLDERED
TO SLEEVE
SINGLE CORE
SHIELDED CABLE
INNER CONDUCTOR
TO ANODE
IR LED
A
SHIELD BRAID
TO CATHODE
Making An IR LED Extension Cable
Depending on how your gear is arranged, you may also
want to make up a cable with a 3.5mm jack plug at one
end and an external IR LED at the other. Fig.12 shows the
details.You will need to use a suitable length of single-core
shielded cable, while the LED leads should be insulated
Fig.12: here’s how to make an IR LED extension cable
if you need one.
from each other using heatshrink tubing.
A larger piece of heatshrink can then be used to cover
the end of the cable, both LED leads and part of the lens.
Par t s Lis t
IR-To-UHF Converter
1 infrared remote control (eg,
Altronics A-1012)
1 double-sided PCB, code
15107131, 20mm x 47mm
1 433MHz transmitter (Jaycar ZW3100, Altronics Z 6900) (TX1)
1 170mm length of yellow light
duty hook-up wire
1 200mm-length red hook-up wire
1 200mm-length green hook-up
wire
1 200mm-length blue hook-up wire
Semiconductors
1 PIC12F675-I/P programmed
with 1510713A.hex (IC1)
1 4N25 or 4N28 optocoupler
(OPTO1)
1 1N4004 1A diode (D1)
Capacitors
2 1µF monolithic ceramic (MMC)
Resistors (0.25W, 1%)
1 47kΩ
1 100Ω
2 1kΩ
UHF-To-IR Converter
1 double-sided PCB, code
15107132, 79 x 47mm
1 UB5 box, 83 x 54 x 31mm
1 front panel label, 78 x 49mm
72 Silicon Chip
K
1 433MHz receiver (Jaycar ZW3102, Altronics Z6905A) (TX1)
1 PCB-mount 2.5mm DC socket
1 3.5mm PCB-mount switched
jack socket
1 DIL8 IC socket
1 170mm-length of light-duty
hookup wire
1 10kΩ miniature horizontal
trimpot (VR1)
Semiconductors
1 PIC12F675-I/P programmed
with 1510713B.hex (IC1)
1 78L05 regulator (REG1)
1 1N4004 1A diode (D1)
1 3mm IR LED (LED1)
1 3mm red LED (LED2)
Capacitors
2 100µF 16V PC electrolytic
1 100nF MKT polyester
Resistors (0.25W, 1%)
2 1kΩ
2 220Ω
Optional
1 3.5mm mono jack plug
1 1m length single core screened
cable
1 3mm IR LED
1 100mm length 3mm-diameter
heatshrink tubing
correct code for your appliance. That
done, test it without the UHF-To-IR
Converter (ie, turn the converter off)
first to ensure the appliance can be
controlled using IR signals only.
Once that works correctly, the unit
can be tested with the UHF-To-IR Converter unit. Note that the converter’s IR
LED should be pointed in the general direction of the appliance to be controlled.
To test it, power up the UHF-To-IR
Converter, cover the IR LED on the
remote with a finger and check that the
appliance can be controlled via the UHF
radio link. If it doesn’t work, adjust VR1
as you operate the remote control until
the appliance responds. Usually, setting
VR1 mid-way (corresponding to a carrier
frequency of 38kHz) will be suitable.
Once it’s operating correctly, try using the remote to control the appliance
from another room. You should get a
free-air range of 30 metres of more but
the range will be less than this inside
a house, depending on any obstacles
(walls, etc) between the remote and
the UHF-To-IR Converter.
Finally, note that the IR receivers in
many appliances are so sensitive that
they will respond to IR signals that are
bounced off the walls or the ceiling of
the room. So experiment before going
to the trouble of making up the extension cable if you can’t aim the IR LED
in the UHF-To-IR Converter directly
SC
towards the appliance.
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