This device allows you to control remotely any (with suitable add-on expansion boards, up to eight) device, such as lights, water heaters (boiler), air-condition, plant watering, alarms, etc via a relay. By using it you can for example water the garden at your country house from the convenience of your living-room, or you may turn on the water heater, or the air—condition at home from your offices so by the time you get there, there will be hot water and the ambient temperature will be as you prefer it. This is done by means of this circuit and a simple digital telephone line or a GSM unit. It is secure as it has a four digit access code and you get a positive confirmation that your command was accepted. Operation of the device is simple, as simple as pressing the proper key sequence on a digital telephone keypad. The system requires a digital line as it is controlled by the. DTMF codes used in modern telephones and CANNOT be used with with the pulses used over the old analogue telephone lines.
- Control (ON-OFF) of an appliance (up to eight with expansion) through telephone.
- Positive confirmation of the device state by sound signals.
- Four-digit security access code.
- Power requirements: 12VDC / 0,5A
- Relay rating: 230V 110A
- Expansion to up to eight channels via a relay board.
- Can be used with a GSM unit if there is no telephone line available.
HOW IT WORKS
The circuit consists of four different stages, easily recognized on the schematic:
- The first stage is the power supply. it uses the voltage regulator LM7805 (IC5), in order to provide +5 VDC to the microprocessor and the
DTMF decoder circuits, and also supplies with 12 VDC the transistors controlling the relays and the relay coils themselves.
- The second stage is built around the HT9170 (IC3) which is a DTMF decoder IC. This stage is responsible for the identification of the access
code and the commands sent to the system.
- The third stage is built around the microprocessor PIC16657 (IC1) and its memory the 93LC4BB (IC2). This is the part of the circuit
which "understands" and executes the command received.
- Finally. the fourth stage consists control circuit with a relay having contacts rated at 10 A which can activate (turn ON) or deactivate (turn OFF)
any device connected to it. following the commands send via telephone to the micro-controller.
- Take care not to overheat the tracks as it is very easy to lift them from the board and break them
- When you are soldering a sensitive component it is good practice to hold the lead from the component side of the board with a pair of long
nose pliers to divert any heat that could possibly damage the component.
- Connect the circuit to a 12V DC power supply +12V.
The programming and control of the unit is done via telephone. To do this. follow the next steps:
1. Connect the device to a digital telephone line. From another line (or a mobile), dial the number of the line that is connected to the device.
2. After the third ring you will hear two short tones (beep—beep).
3. Enter the key sequence of the access code (the Initial code number is 1234, a number which you may change easily later on).
4. If you have entered the access code correctly, you will hear again two short tones (beep-beep). otherwise you will hear-a protracted tone
(beeeeep). If the access code is not entered correctly. after the third attempt. the device will drop the line and terminate the connection. This is
a safety measure against tampering with the controller.
5. Once you achieve a successful connection to the remote control device, press *1. This way the device activates the relay turning the
appliance connected to it ON. If you want to deactivate the relay. simply press #1.
6. If you want to check the state of the system, enter 1. If you hear a protracted tone (beeeeep) the device is OFF. If you hear two short tones
(beep-beep), the device is ON.
CHANGE OF ACCESS CODE
If you want to change the original four digit access code, pick up the handset of a telephone connected in parallel to the device, and press the
button switch LEARN (S1). When you hear four short tones (beep-beep—beep-beep) you may enter the new four digit access code. You will
hear four short tones again. which means that the change has been successfully accepted.
IF IT DOESN'T WORK
- Check your work for cold joints, bridges across adjacent tracks or soldering flux residues that may cause problems.
- Check all the external connections to and from the circuit.
- See that there are no missing or misplaced components.
- Make sure that all the polarized components have been soldered the right way round.
- Make sure that the supply has the right voltage and polarity.
- Check your project for faulty or damaged components.
If everything checks and your project still fails to work, please contact your retailer and the Smart Kit Service will repair it for you.
PCB, 4 Pins, 8 DIL socket, 18 DIL socket, 2 x 14-pin strips to form a 28 DIL socket for the IC1
microprocessor, 10 pin expansion pinstrip, small P type heatsink for IC5.
The remote controller can be used as we have already mentioned with a digital telephone landline or with a suitable GSM module which behaves as a line. This makes it suitable for use In places where it is not practical or desirable to have a permanent telephone connection. If you find that you need more flexibility you can add more relays (up to a total of 8) by means of special expansion boards.