Typical applications include:-
Domestic and commercial security Guard patrol/lone worker protection Medical
Alert/Nurse Call system Mobile panic attack Computer networking Remote industrial
process monitoring Data transfer through hazardous environments Lighting
control, Garage door openers Fire alarms Picture/antique protection alarms
Remote control, Access control |
| |
Absolute Maximum Rating
| Supply voltage Vcc (pin 13) |
-0.3V to +8.0V |
| RF input (pin 1) |
0dBm |
| Any input or out put pin |
0.3V to Vcc V, ± 10mA |
| Operating temperature |
0° C to +40° C |
| Storage temperature |
-40° C to 100° C |
Performance Data
|
| |
| ambient temperature |
20° C |
| supply voltage |
+5.0V unless noted otherwise |
| test circuit |
Fig 3 |
|
| |
| Parameter |
Min |
Typical |
Max |
Units |
Notes |
| Operating supply range (Vcc) pin 13 |
4.5 |
5.0 |
5.5 |
V |
|
| Supply current pin 13 |
17 |
21 |
27 |
ma |
|
| Receive frequency |
- |
433.92/418 |
- |
MHz |
|
| Overall frequency accuracy |
-80 |
0 |
+80 |
kHz |
1 |
| Sensitivity for 10dB S/N pin 1 |
- |
0.5 |
1.0 |
µV |
2 |
| Sensitivity for 20dB S/N pin 1 |
- |
1.0 |
2.0 |
µV |
2 |
| Jam det, threshold pin 1 |
- |
10 |
- |
µV |
|
| Carrier det, threshold pin 1 |
- |
3 |
- |
µV |
|
| RF input impedance pin 1 |
- |
50 |
- |
W |
|
| IF bandwidth |
- |
250 |
- |
kHz |
3 |
| AF output level pin 4 |
- |
400 |
- |
mVpp |
2,3 |
| AF bandwidth, -3dB pin 4 |
DC |
- |
10 |
kHz |
4 |
| Logic low, pin 6,8,10,11 |
0 |
0.2 |
0.5 |
V |
5 |
| Logic high, pin 6,8,10,11 |
4.5 |
5 |
5 |
V |
6 |
| Antenna tamper detector pin 1 |
0 |
- |
5 |
kW |
9 |
| Sig. strength dynamic range pin 9 |
20 |
30 |
- |
dB |
|
| Sig. strength FSD pin 9 |
3.0 |
3.3 |
3.6 |
V |
|
| Sig. strength O/P resistance pin 9 |
6.6 |
6.8 |
7.0 |
kW |
|
| enable time pin 11 |
- |
- |
5 |
ms |
3,7 |
| signal detect time pin 11 |
- |
- |
3 |
ms |
3,8 |
|
 |
| |
| Notes: |
Temperature 0° C to 40° C ± 25 kHz deviation, 2 kHz tone 3m V input
The conversion slope is -ve on the 418 MHz version 10mA sink No
load, (from 22kW internal pile up) From application of supply to
carrier detect low From application of signal to carrier detect
low For logic high on pin 8
|
|
| |
Fig 1: Mechanical details. |
| |
| Pin Description
|
| |
| pin 1 |
RF IN |
The receiver antenna connects to this 50W
input.A 22 kW pull up resistor, internal to the module is used for
‘tamper’ sensing on this pin. |
| pin 2 |
RF GND |
This pin should be connected to any ground
plane against which the antenna works.It is internally connected to
pin 3,14,15 & 16 |
| pin 3 |
0V |
Ground for supply |
| pin 4 |
AF |
This is the FM demodulator output. It has
an output impedance of 330W and a standing
DC bias of approximately Vcc/2 |
| pin 5 |
Min |
The voltage on this pin is the peak -ve
at pin4 (AF). A resistor between this in and pin 7 (Max)controls the
data slicer’s transient response. |
| Pin 6 |
Data out |
This CMOS compatible output from the data
slicer is a squared version of the signal on pin 4 (AF).This signal
is used to drive external digital decoders, it is true data (i.e.:
as fed to the transmitters data input). |
| pin 7 |
Max |
The voltage on this pin is the peak +ve
at pin 4 (AF). |
| pin 8 |
Tamper |
This CMOS compatible output goes low if
the DC resistance of the antenna exceeds 5kW
to 0V. |
| Pin 9 |
RSSI |
Received Signal Strength Indicator. 0V
to 3.3V. |
| Pin 10 |
JAM |
This CMOS compatible output goes low when
a strong greater than a period of time determined by a capacitor on
pin 12 (JAM TC) |
| pin 11 |
DET |
This CMOS compatible output goes low when
an incoming signal has sufficient strength to provide a clean
decodable signal at pin 6 (DATA). |
| pin 12 |
JAM TC |
A capacitor between this pin and ground
controls the jamming detectors delay time. |
| Pin 13 |
Vcc |
Positive supply of 5V ± 10%. The supply
must be clean, stable (<10mV ac) and free of high frequency digital
noise. A 10mF supply decoupling capacitor is recommended. |
| Pin 14,15,16 |
0V |
Ground to earth plane |
|
|
| |
Typical Performance Data
| ambient temperature |
20° C |
| supply voltage |
+5.0V |
| test circuit |
Figure 3 |
|
| |
|
Fig 2: Graph : Performance Data |
|
Fig 3: Test Circuit |
|
Fig 4: Internal Block Diagram |
| |
Application
Notes
The simplest applications of the module requires only three connections,
+5V supply, ground and the data output. A simple quarter wave antenna (17cm
of wire or track
on pin 1) will give good results. A 10 µF supply decoupling capacitor is
recommended directly on pin13 |
| |
ANTENNA
The positioning of the antenna is of the utmost importance and is the main
determining factor of system range, the following notes should assist in
obtaining optimum performance:-
Keep it clear of other metal in the system, particularly the ‘hot’
end. The best position by far, is sticking out the top of the product. This
is often not desirable for practical/ergonomic reasons thus a compromise
may need to be reached. If an internal antenna must be used try to keep
it away from other metal components, particularly large ones like transformers,
batteries and PCB tracks/earth plane. The space around the antenna is as
important as the antenna itself.
Keep it away from interference sources, bad interference can easily reduce
system range by a factor of 5. High speed logic is one of the worst in this
respect, fast logic edges have harmonics which extend into the UHF band
and the PCB tracks radiate these harmonics most efficiently.
Single chip microprocessors and ground planed logic boards reduce this problem
significantly. A simple test for interference is to monitor the RSSI output
of the receiver, there should be no change in the reading when the logic
circuits are run or held reset. Interference can also be easily identified
by listening to the AF output of the receiver, smooth white noise should
be heard. |
| |
ANTENNA TYPES
Any of the integral antenna shown in the data sheet for the transmitter
module (TXM-433) is suitable for use on the receiver. Additionally a coax
fed external dipole or ¼ wave ground plane antenna may be considered if
system range is paramount. A 2.2kW resistor wired
across the coax at the antenna end will allow tamper detection (cutting)
of the coax using at the tamper sense facility in the receive module; pin
8 will go low if the coax is cut. |
|
| |
DATA SLICER
A CMOS compatible data output is available on pin 6, this output is normally
used to drive a digital decoder IC or a microprocessor which is performing
the data decoding. The signal detect output on pin 11 may be used to gate
the data output before it is supplied to a decoder, however this should
only be done on systems with ‘weak’ digital coding i.e. where
there is a danger of the decoder giving false outputs on the ‘noise
data’ which is present on pin 6 when no valid signals are being received.
Systems with good CRC, checksum or repeat code verification will not require
the ‘noise data’ to be gated off and as a result will be able
to decode weaker signals (i.e. greater range).
The data detect output on pin 11 is normally used for duty cycle power saving
for portable equipment where battery life is a problem. By pulsing the receiver
on/off the average supply current may often be reduced by a factor of 20
or more depending upon the system requirements, the data detect output is
valid 5ms after application of the supply and is used to inhibit the power
saving while data decoding is done.
The data slicer in the receiver module is designed to accept data with a
wide range of pulse widths and mark: space ratio’s. The voltage waveform
on pin 4 (AF) is fed to 2 peak detectors, one +ve, one -ve and a comparator
threshold is set half way between the max and min voltage, a small amount
of hysterisis is applied. The data on pin 6 is the output of this comparator.
The date slicer has a transient response time, this is the settling time/hold
time of the peak detectors. It is programmable by an external resistor between
pin 5 & 7 (min & max). With no resistor fitted (normal use) the
data slicer settles in approx. 300ms from reception of a coded signal (i.e.
the first 300ms of signal may be corrupt at the data output) and will pass
pulse widths up to 50 ms of continuous 1 or 0. |
| |
| A resistor between pin’s
5 & 7 shortens these time i.e. |
|
Resistor Value
(pin 5 to 7)
|
Code Preamble
(minimum length)
|
Longest 1 or 0 allowed |
|
Open Circuit
|
300ms
|
50ms
|
|
1 MW
|
150ms |
25ms |
| 220 kW |
30ms |
5ms |
| 47 kW |
7.5ms |
1.3ms |
|
| |
|
| |
JAMMING DETECTOR
provides a logic 0 on pin 10 when a strong signal of
greater than 10m V is being received. The detector may be set to give a
delayed output by connecting an electrolytic capacitor between pin 12 (JAM
TC) and 0V. The delay is approximately 0.7s / mF ( i.e.: a 10mF capacitor
will need the jamming signal to be present for 7s before pin 10 goes low).
The delay time will be subject to the electrolytic’s tolerance so may
vary widely. For accurate/long delays it is recommended that a delay of
7s (10mF) to be used and the jam signal be fed to a digital timer to determine
the required delay. |
| |
AF OUTPUT
This output is the FM demodulator’s output after
buffering and de-emphasis. Since it is taken before the data slicer in the
module, it may be used to drive external data slicers/demodulators in cases
where the internal data slicer is not suitable. This is the case where an
analogue subcarrier is being employed e.g. 2 tone AFSK or DTMF tones. In
these cases the AF Output is used to drive the FSK/DTMF decoder directly.
The AF Output is also a very useful test point for listening for signals
or interference. The output will drive low impedance headphones via a 10mF
DC blocking capacitor for monitoring purposes. The phones should not be
left connected during normal system operation as their low impedance will
cause a certain amount of audio distortion which may upset the on board
data slicer, if permanent audio monitoring is required a Hi-Z (>1kW
) buffer should be used to drive the headphones.
The AF Output is DC coupled to the FM demodulator thus the DC level varies
with the frequency of the incoming signal and may be used to check frequency
shifts / drifts between the transmitter and receiver. |
|
| |
Note
The polarity of this signal is different on different
frequency versions of the module, check the specific data sheet for polarity.
|
| |
RSSI
(Signal Strength) OUTPUT
This is also very useful for monitoring the performance of the radio link.
It is a 0V to 3.3V signal which increases logarithmically with increasing
incoming signal strength. There is an internal 6.8kW
resistor is series with this output so that a 0.5mA fsd meter may be connected
directly to this output for monitoring purposes. In more sophisticated systems
this signal may be fed to an A-D converter to automatically monitor the
integrity of the radio link. |
| |
Additional Reading
| BS 6799 |
British Standard for Wire-free intruder alarm systems |
| BS 4737 |
British Standard for Intruder alarm systems in buildings
from British Standards Institution. Tel: 020 7629 9000 |
| MPT1340 |
DTI type approval specification for 418MHz Telemetry
from Department of Trade and Industry.
Tel: 0171 211 0502 or 0171 211 0505.
e-mail: library@ra.gtnet.gov.uk |
| ARRL HAND BOOK |
Excellent radio engineering text |
| ARRL ANTENNA BOOK |
Practical antenna design book from Radio Society of
Great Britain. Tel: 01707 659 015 or 01707 663 279 |
|
|
|
Limitation of liability
The information furnished by Radiometrix Ltd is believed to be accurate
and reliable. Radiometrix Ltd reserves the right to make changes or improvements
in the design, specification or manufacture of its subassembly products
without notice. Radiometrix Ltd does not assume any liability arising
from the application or use of any product or circuit described herein,
nor for any infringements of patents or other rights of third parties
which may result from the use of its products. This data sheet neither
states nor implies warranty of any kind, including fitness for any particular
application. These radio devices may be subject to radio interference
and may not function as intended if interference is present. We do NOT
recommend their use for life critical applications.
The Intrastat commodity code for all our modules is: 8542 6000.
R&TTE Directive
After 7 April 2001 the manufacturer can only place finished product
on the market under the provisions of the R&TTE Directive. Equipment
within the scope of the R&TTE Directive may demonstrate compliance
to the essential requirements specified in Article 3 of the Directive,
as appropriate to the particular equipment.
Further details are available on The Office of Communications (Ofcom)
web site:
Licensing
policy manual
|
 |
Right: TXM Transmitter