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Features
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| Kit Contents
The CTR44 Evaluation Kit is supplied with the following contents:
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Additional optional requirements
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| General description
Evaluation Kit uses a common PCB for both Encoder and Decoder just like CTR44-000 IC can be used as either Encoder or Decoder. However, the modes cannot be changed on the evaluation kit as PCBs are populated with necessary components for respective mode. Decoder PCB can be easily identified by the noticeable presence of relays. |
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| Visual Indication
The following status LEDs will be activated
depending on the status of CTR44.
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Quick Functionality Guide
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| On-board low drop out regulator (LE50CZ) provides
clean regulated 5V supply to the radio modules and microcontroller.
However, the relay coils are powered from the external power supply
or on-board 9V alkaline battery via 1N4001 diode (0.7<VF<1.1V)
for protection against accidental reverse supply connection. Although
12V relays are used, the minimum pull-in voltage for relay coil is
8.4V.
Copper on all unused PCB area connected to 0V, provides ground plane necessary for the ¼ wavelength monopole antenna to perform efficiently. At VHF frequencies, the ground plane dimension is not sufficient for a ¼ wavelength whip antenna. A helical antenna would perform better compared to a ¼ wavelength monopole antenna without proper ground plane as it does not rely on ground plane as much as a monopole. Sockets are provided for easy insertion of radio modules. However, long pins and the large gap between ground plane of the Evaluation Kit PCB and ground plane of the module will degrade the range performance of the module. In a finished product, the SIL type modules should be mounted flat on the PCB with their pins trimmed to bare minimum. Can lugs, which are pre-soldered to ground plane of the module, should also be soldered to ground plane pads on the main PCB of the product. Frequency of the ceramic resonator (RES) can be decreased (e.g. 2MHz) to reduce the bit rate (1200bps) through radio when using radio receiver with reduced bandwidth optimised for longer range. For fast activation, it can also be increased up to 20MHz, however, the CTR44-000-DIL should be replaced with CTR44H-000-DIL which provides higher drive level for >4MHz resonator to oscillate. |
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CTR44 Encoder Board In this mode, jumper link (JP1) connects the MODE pin of the CTR44-000-DIL to 5V supply line. RST pin is also tied to 5V. 5V supply to CTR44 IC is decoupled close to its VCC pin via 100nF Ceramic capacitor (C1). CTR44 has an internal weak pull-up to 5V on its Address and Data pins. Therefore the DIL switches when switched ON shorts the respective pin to 0V. Therefore, address/data bit values are inverted relative to switch positions. Address and Data Switch number starts from 1 instead of 0. (SW2 No 2=DB1) PNP transistor (T4) is used to Enable and supply power to SIL type transmitters. It inverts the Active Low TXE from CTR44 to Active High Enable for TX1/TX3A and connects supply to module when switched ON. |
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Setup
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CTR44 will execute a power-up transmission when switched ON just after procedure 7. TX LED will be momentarily lit followed by DB LEDs for which Data Switch was set to OFF position. Relay will make a 'clicking sound' when the internal relay switch positions are changed. This power-up transmission feature can be used for low cost remote control which requires a single switch/button operation with default address and data. If the SEND button switch (SW3) is pressed intermittently, the Encoder PCB will transmit a short bursts of Address and Data switch settings to decoder PCB. Instead of holding the depressed SEND button, the Jumper JP2 can be used for continuous transmission which allows user to dynamically change data switches. When performing range test, the SEND Jumper (JP2) should be inserted on the Encoder PCB to transmit continuously from a fixed location. User can walk around with the Decoder PCB and monitor the status of OK and DB3:DB0 LEDs. |
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| CTR44 Decoder Board
It is populated with additional components to drive the Relay and provide visual indication of received data bits. NPN transistors (T3:T0) will provide the required drive current and voltage drop to activate relay coil to pull-in the internal relay switch and to activate the LEDs if the received data bit is '1'. Diodes (D7:D4) provide protection against back EMF developed by the relay coil when switching OFF. Since the STROBE pulse signal generated by the CTR44 is 10ms long, OK LED output may not be visible in bright sunlight. |
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Setup
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| SAFETY WARNING:
Extra care should be taken when handling the electrical connection
from relay to 250AC device. Mains power should be disconnected before
connecting the wires to 3-way terminal blocks to prevent electric
shock. Exposed wires or terminal block should not be touched during
evaluation.
LATCH Jumper (JP2) can be used to hold the received data bit value (Relay Position) without continuously transmitting the same data bit values. Relay position can be updated and maintained with a momentary update transmission after adjusting Data Switch positions on the Encoder PCB. When performing range test, the Latch Jumper (JP2) should be removed to notice loss of reception when the DB3:DB0 LED starts to flicker. Flickering indicates that the receiver is beyond its maximum reliable operating range or in weak RF signal reception area where some of the packets are correctly received while others are lost. In building environment, DB LED may stop working even though receiver may be within its operating range due to 'null-spot'. Moving the position or orientation the decoder (antenna) will enable receiver to continue to receive sufficient RF signal level for decoder to correctly decode the transmitted data. The above procedures can be used in a site
survey to identify areas of weak RF signal reception, null-spots
and to find best position for antenna placement to maximise coverage. |
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Figure 2: Schematic of CTR44 Evaluation Kit
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Figure 3: Component layout of CTR44 Evaluation
Kit PCB |
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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. 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. |
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