Allows to operate by remote radio-so-a boiler or air conditioner using a conventional thermostat which is coupled an RF link encrypted. The transmitter is connected to the thermostat and the receiver is placed near the furnace or air conditioner. The scope of the system is sufficient for an apartment or villa.
When trying to install a new appliance in an apartment already equipped and manned, especially whether to integrate with the existing electrical installation and that is not very close to a decision, we must choose between two equally unsatisfactory options: to create the new circuit portion with exposed pipes (tubes and clamps or glued chute, etc..), which is not aesthetic, or the mixer (corrugated conduit bleeding in a building to practice in dubbing or-worse-in the wall), implying a dusty construction site hardly compatible with the current occupation of the premises.
If the device in question is the thermostat for a boiler or an air conditioner (heating / cooling), etc.. and we did not realize at the second implementation of the apartment as a thermostat "integrated" to the heater or air conditioning is not effective or accurate and it is much better place the remote thermostat in the room furthest to heat or cool, well the solution "data transfer thermostatic radio" allows the most rational way to avoid work, we said, the rendered unattractive or difficult to live performance. The system
two remote units TX / RX this article we will achieve is a coded UHF radio link at 433.92 MHz coupled to a thermostat to normal: it is located away from the furnace or air conditioner (in the room furthest from or the one we want to focus) and it controls the transmitter TX which is near him (in fact, it passes data thermostatic which the microcontroller draws a flow modulating radio carrier issued by TX).
from the furnace or air conditioner, etc.., Is the unit RX (receiver) that receives this carrier modulated by the data flow thermostat, demodulates (retrieve data), which will essentially make it stick or put to rest the relay output of the receiver: this output relay that controls the thermostat located on the boiler or air conditioner, etc..
Our system can be likened to a radio controlled, What differs is that instead of closing the ignition of the heater / air conditioning and remote, when the temperature is reached, stop - implying a continuing issue, our transmitter sends the start command or passes it off as the thermostat neighbor, then waits, which is very economical and can be content with two button batteries.
That at least the major, but we will see more than the receiver can learn the code of the transmitter, which, if you're a faithful reader of our magazine should not surprise you! We will start by analyzing the operation of the TX unit, then we will do the same for the RX unit and finally we move on to the practical realization of the two plates. 
issuer
The wiring diagram Figure 1 shows that the microcontroller and the module TX UHF Aurel constitute all of the active components of this first unit. After initializing the I / O PIC12F675 resident program (this program is EF614TX) tests continuously GP5 line to verify the logic: When IN points are isolated, the pull-set internally by the software determines the logic high and when the remote thermostat (located near the transmitter and connected to it) closes the input IN, the GP5 goes to logic low. In both cases the microphone periodically transmits status data from the IN (or the data from the thermostat) to the receiver located near the furnace or air conditioner to operate.
mode of operation is set using the dip-switch with two microswitches DS1, or the logic state of the two lines GP3 and GP3. About the latter, note one detail: GP1 whereas it is possible to set the pull-up resistor internal to the PIC GP3 however does not allow that, so it was necessary to link R3 from pin 4 of U1 and the positive supply. Modes of transmission of the state of the thermostat (which will become the state of the boiler or air conditioner) are four in number (2 ^ 2 since there are two microswitches for two positions):
- the first mode (the two microswitches open) provides for sending the command to each change of logic state of input IN;
the receiver immediately executes the command received;
- the second (open-mint1 MinT2 closed) transmission combines the change of state of IN (ie mode 1) with all the periodic repetition three hours of the condition of the IN, as in the first mode, the receiver does not follow that incoming orders;
- the third fashion (mint1 fermémint2 open) is similar to the previous one but increased the period of three to one hour, however the receiver has a safety mechanism to open the relay and turn off the boiler in the event, at the end 'quarter past one, the last condition was not renewed transmitted;
- the fourth and last mode (the two micro-switches closed) provides for the transmission of the state change and the periodic renewal every three hours' s there is no change in the meantime, the receiver performs the change orders and always safe, if since the last transmission of change does not receive confirmation of TX for quarter past three, he put the torch to rest. Like all systems, remote control, although designed to cover a distance of several tens of meters, our radio remote has a code in order to prevent the sender to disrupt other systems operating on the same frequency and the receiver to be activated unexpectedly by an issuer not part of the same system. In addition, to avoid having two pair TX / RX neighbors (eg in two villas binoculars or two apartments in the same building) interfere with each other, it was anticipated the possibility of defining several codes: five combinations, it seems unlikely, but in reality it is quite enough as it is unlikely that using more than two or three thermostats UHF in the same room.
But if you take a look at the wiring diagram, you're probably wondering where are the components that operate this coding? Well, the setup is done when the circuit power: after a rapid sequence of ignitions, LD1 flashes slowly for about 5 seconds (2 s on, 1 s off) to start programming the address identifies the system must change the state of mint1 during the slow flash. LD1 is then a sequence of quick flashes interspersed extinctions (it five times). To set the address must submit mint1 in its original position when LD1 has accomplished a number of quick flashes and equal to the number of extinctions sought: for example, if one wants to choose the address you have to wait 3 that LD1 has completed three cycles of quick flashes and extinctions. When mint1 has been restored to its original position (that is to say in which he found himself at the time of powering up the circuit), the software confirms the setting by a sequence of flashes slow LD1.
Note that each power up, if you do not access the setup procedure, after the initial rapid blinking and flashing 2 s / 1 s, the circuit shows the current address: to view, we must leave the switches as they are and wait for the flashing 2 s / 1 s pulse at a time LD1 the number of times (up to 5) corresponding to the address set. You will see you when you change the batteries in the TX. When the transmitter module, every transmission it sends the form of pulse trains 0 / 3 V, the data corresponding to the command and address, along with information needed to identify the transmission.
Each stream is sent to the following format: you start with the header (header), each composed of U expressed by the binary number corresponding to the value of the standard ASCII, followed by *, then comes the command , in text format, again, each letter is expressed by its ASCII value (in binary).
follows function, as a number (1, 2, 3, 4) corresponding to control mode, after the number Fashion is the code coupling (1-5) which is transmitted, the flow ends with a series of A expressed by binary numbers corresponding to their ASCII value.
The pulses are transmitted through pin 3 and then routed to pin 2 of U2 hybrid module: it is a transmitter CMS designed by Aurel to operate at low voltage (2.7 to 5 V), its oscillator is PLL quartz and transmits its UHF radio carrier at 433.92 MHz (exact and stable), the output power is 10 dBm. The wave is emitted by the antenna pin (11) when the input line (2) is subjected to a high level TTL ; To logical zero the oscillator stops. A pin antenna can connect a simple piece of copper wire of 17 centimeters, which guarantees a range of 50 to 60 meters.
But nobody prevents you need to increase this range by connecting an antenna ANT developed 50 ohms impedance and of course cut for this frequency.
Figure 1: Diagram of the transmitter for radio control thermostat.
Figure 2: Schematic implementation of the components of the transmitter for radio control thermostat.
Figure 2b : Dessin, à l’échelle 1, du circuit imprimé de l’émetteur de radiocommande pour thermostat. 
Figure 3 : Photo d’un des prototypes de l’émetteur de radiocommande pour thermostat. 
Liste des composants R1 .. ... 470 R2 ... .. 4,7 k R3 .... . 4,7 k
C1 ...... 100 nF multicouche C2 ...... 220 μF 16 V électrolytique
C3 ...... 220 μF 16 V électrolytique D1 ... .. 1N4007 LD1 . .. LED 3 mm verte DS1 . .. dip-switch à 2 microinterrupteurs T1 ...... BC557
U1 ...... PIC12F675-EF614TX already programmed in the factory U2 ...... TX4MAVPF10
Miscellaneous:
a support 2 x 4 1 terminal 2 pole
2 battery holder for CR2032 CR2032 button batteries
2
a plastic housing appropriate (opt.)
Unless otherwise specified, all resistors are 1 / 4 W 5%.
receiver
-Come with a look this time at the circuit diagram in Figure 4 - what happens when the RX receives a data stream from the TX. The wiring diagram shows a circuit consisting mainly a hybrid module radio receiver and a microcontroller.
After initializing the I / O PIC12F675 resident program (this program is EF614RX) monitoring lines GP0 and GP4: it detects with the first arrival data of the radio and tested it with the second state the push that the user uses to impose self-learning process. But
proceed in order from the receiving antenna: it is connected to pin 3 and routes the RF signal received by the input of U3, a hybrid module Aurel RX4M50FM60SF, superheterodyne receiver (That is to say, frequency conversion) with high sensitivity (-111 dBm) and selectivity (600 kHz at -3 dB), the demodulated signal and quadrature set is available on pin 14.
When it detects a switch on the line GP0, the microcontroller knows that a stream has been sent by the issuer, he transferred into RAM and analysis to verify, before all, that is the format adopted for the system, if so, it extracts the address to verify that the command comes from the TX well coupled, otherwise it suspends the proceedings on hold and returns a new GP0 and GP4 switching. If the stream is consistent with the protocol and it is really from the emitter coupled, the command is decrypted and the user is read (this mode is transmitted and constantly updated).
Two situations can arise: the state passed is different from that which is currently in the relay, in which case the line GP2 is set to put the relay in the requirement.
If, however, control returns to confirm the current status of the relay, it is ignored: the output controls the relay remains in the same condition.
The active contact of RL1 is NO (normally open) when you want to activate a boiler when the activation command is received (items IN the issuer closed) puts the microphone GP2 to logic high, saturated T1 and the closing itself, however, in the presence of a deactivation command (opening IN contact the issuer), GP2 is zero and let T1 prohibited, which puts to rest the relay and opens OUT NO. The program running in the PIC is designed to maintain the order received until receipt of an order opposite or in the modes that provide, until the passage of time limit during which the PIC has to wait flow confirmation from the transmitter. This means that if the relay is activated, it remains until the TX sends a stream containing the opposite command (OFF) or in modes 3 and 4 until the end of the period (1:15 'for the 3 and 3:15, for 4) without confirmation of arrival of periodic flows. So much for
GP0; however if the detected event relates to the switching GP4, this means that the user has pressed the button with which requires launching the coupling procedure TX / RX: if you press this button, the PIC flashes 5 times LD2, which is then kept in continuous light until that a stream is received from the transmitter (to force the transmitter to send it, just change the state of the IN, or open it if it is closed or shut down if it is open ). When data arrives, the micro transfer them into RAM and analysis to verify everything before they have well format system, and if so, it extracts the address it stores in EEPROM to control flows arriving during normal exercise and rest assured that the orders are from the TX well coupled, otherwise it aborts the procedure and returns to waiting for a new switching GP0 or GP4. When the address is saved, LD2 first flashes 5 times then goes out quickly; this signal confirms the acquisition of the code, and coupling the receiver with the transmitter which has just completed a transmission.
However, the circuit has two LED LD1 will turn on when the relay (and hence the output of the boiler control) is turned on and off when at rest, however LD2, further proceedings Self-study we have just seen in normal exercise blink when a stream coupled from the TX. The receiver in its entirety is supplied with a DC or AC voltage of 12 V or 9, applied to the points + and PWR-D1, which in the first case provides protection against accidental reversal of polarity, with alternating single rotation straightens the 50 Hz sine sector In both cases, the ends of C1 and C2 we find a voltage supplying the relay winding, through the regulator U2, we reduce this voltage to 5 V stabilized we need to run the PIC and the hybrid module receiver Aurel. Figure 4: Diagram of the receiver for radio control thermostat.
Figure 5a: Schematic implementation of the components of the receiver for radio control thermostat.
Figure 5b: Drawing scale 1, the circuit board receiver for remote control thermostat. 
Figure 6: Photograph of a prototype receiver for remote control thermostat. 
Iist R1 ...... R2 4.7 k ...... 10 k R3 ...... R4 1 k
...... 330 C1 ...... 100 nF multilayer
C2 ...... 220 uF 25 V electrolytic C3 ...... 100 nF multilayer C4 ...... 220 uF 16V electrolytic D1 ...... D2 1N4007 ...... 1N4007
LD1 ..... LED 5 mm red LD2 ..... Green LED 5 mm T1 ...... BC547
U1 ...... PIC12F675-EF614RX already programmed in the factory
U2 ...... 7805
U3 ...... RX4M50FM60
P1 ...... micropoussoir
RL1 ..... relay 12 V
Miscellaneous:
a support 2 x 4 1 terminal 3 pole
an outlet
an 8 mm bolt 3MA
a plastic housing adapted (opt.)
Unless otherwise specified, all resistors are 1 / 4 W 5%.
The practical realization of the transmitter and receiver
The practical realization of this thermostat controlled remotely by radio is fairly simple although it must achieve two decks, one for TX and one for the RX.
Figure 7: The radiothermostat consists of two units. The transmitter, controlled by the contact of the thermostat itself and the receiver has a relay whose contacts NO and NC are available for controlling a boiler or air conditioner. The transmitter is powered by two "buttons" CR2032.
Figure 8: The communication protocol.
Anytime the thermostat connected to the TX data stream is sent, the format still the same, is interpreted by the microcontroller of the receiver who knows the syntax of the sentence he receives, the format of the data stream is as follows :
header (ASCII) - * / - control - staff - address - Terminator The "header" (header) is the head, precisely, that is to say the beginning that identifies the flow and it consists of a series of capital letters U each expressed with the binary value corresponding to their ASCII equivalent, or 85 (decimal). * / Is a fixed parameter, expressed, as usual, with binary numbers corresponding to the ASCII values of the different symbols (the asterisk 42 and 47 bar). Command can be on or off and is sent as a text composed of characters each expressed by its own value ASCII function is a number equal to 1, 2, 3, 4, by setting the DIP switches of the transmitter : corresponds to the selected mode and is always issued in order to update the configuration of the receiver, which allows him to retrieve the status of output even after a power outage. The parameter Address is the address (!) Of the transmitter and the receiver when it is used it must learn the rules of the issuer and which it is coupled, normal mode, to ensure the order arrives well in TX. Terminator (cap) is the end of the message and consists of a series of uppercase letters A, each expressed by the corresponding binary value (65 decimal) in the standard table of ASCII characters. When he receives a stream, the receiver checks the microphone before it all starts well with a series of U, otherwise it does not go away and waits for new flows arriving from the output of the hybrid receiver module. Note that each program the TX always sends all relevant parameters: this mode of operation has been designed to simplify the procedures (the show actually serves to control the receiver and to update the status of the relay or carry, by learning, coupled to the transmitter and receiver).
Figure 9: The output contacts.
The relay that we mounted on the prototype receiver-type high voltage but it can not switch as relatively common low, around 1 A. This implies that it is used to close the contact of the thermostat is mechanical or electromechanical and not the main supply line, which conveys much larger currents (especially to air conditioners) that what may switch contact of RL1. That said, our transfer system thermostatically controlled by radio may be associated with all types of thermostats available on the market, whether mechanical or electronic, provided that the contact is clean.
The practical realization of the issuer
The plate consists of a single sided PCB, which 2b gives a scale drawing. Start by inserting the support of the ICP and carefully check your welds (or short-circuit between tracks or pads or cold solder joints). Insert and then solder all components (as shown in Figures 2a and 3), continuing with resistors, capacitors, diode, LED, DIP switch, the transistor and ending with "devices": the two clips button batteries, the terminal two poles and then the hybrid module transmitter (up to standing). Attention to the orientation of components polarized: ICP (mark-keyed U to R2, but insert it at the very end), diode, LED, transistor and electrolytic (C3 coated is mounted). Place two button batteries (the + is the visible face of the stack). A copper wire of 17 cm, welded point ANT, is the transmitting antenna.
That's the transmitter board.
The practical realization of the receiver
The deck is also a single sided PCB, which Figure 5b shows the scale drawing 1. Start by inserting the support of the ICP and carefully check your welds (or short-circuit between tracks or pads or cold solder joints). Insert and then solder all components (as shown in Figures 5a and 6), continuing with resistors, capacitors, diodes, LEDs, transistors, the control (without coated heatsink mounted and secured by a bolt 3MA) and ending with "peripheral": relay, three-pole terminal, the jack "jack" power hybrid module and finally the receiver (to standing up). Attention to the orientation of polarized components: ICP (mark-keyed U outward, but insert at the very end), diodes, LED, transistor and electrolytic (both stood up this time). A copper wire of 17 cm, welded point ANT, is the receiving antenna. So much for platinum receiver.
The installation and use
You can now install the plates in two plastic boxes of appropriate size and then integrate them directly to the apartment to the TX associated with the thermostat and the boiler or conditioner for the receiver.
On the transmitter board you mounted a two-pole terminal block at 5 mm pitch: it will facilitate connections with the contact of the thermostat. As for the receiver's terminal three poles at 5 mm pitch facilitate liaison with the contact activation of the boiler. In this connection, usually specify boilers and heat pumps begin to operate when they close their contact activation, so you must use the terminals corresponding to points C and NO RL1, however if you need to order a device that when activated opens its contact activation, use the terminals C and NC. These are also used when one wants to use a single thermostat contact remotely manage an air conditioner (or reversible air conditioning): indeed, the heating thermostats open their contact when the temperature increasing, reaches the set value and close when it goes below it, so The relay closes when the air becomes cool enough and if you use contacts C / NC the air conditioning turns off when the thermostat detects that the ambient temperature is lowered to the desired level, opens its contact. Still on the relay, forget, his touch can accept a maximum voltage of 250 VAC for a current not exceeding 1 A: what you can control the contact activation of a boiler or air conditioning, but not to act directly on the main power supply of these devices, the power far exceeds that of the relay. To make autonomous transmitter, we have supplied with two button cell batteries (for inclusion in their clips, positive outward, répétonsle). The receiver is placed near the boiler or air conditioning, we may conveniently be powered from the voltage from 12 to 15 V (AC or DC) from a small power supply (or a single transformer): the current it (Or he) will be able to provide at least 150 mA.
note that the power outlet that you mounted on the plate receiver is a "jack" to positive in the center (so take a power supply over a jack of the same diameter and the same polarity). Feed
both TX and RX units and check the operation of the system by forcing the issue from the TX (for this, vary the condition of the IN) after pressing the P1 receptor.
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