STEP BY STEP | Beepaway

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Step by Step

Step 1 - Power Regulator

This project’s implementation must be divided into 4 elementary steps in order to provide coherency and ease of understanding for the final electronic scheme.

The radio wave receiver requires a 5V constant feed and, due to the fact that we had a 9V volt battery to work with, a simple power regulator had to be constructed. The small circuit depicted in the figure does this job.

Step 2 - Transmitter

Having done and tested our power feed, we begin by mounting the transmitter circuit as it is stated in its datasheet. This transmitter can operate with voltages between 3V and 12 V but, for simplicity, we chose to feed it with the same 5V input that comes from our power regulator.

As it is possible to see in the picture, it was necessary to use a HT12E enconder in order to manipulate the desired information to achieve correct communication between the transmitter and receiver.

HT12E Encoder IC will convert the 4 bit parallel data given to pins D0 – D3 to serial data and will be available at DOUT. This output serial data is given to ASK RF Transmitter. Address inputs A0 – A7 can be used to provide data security and can be connected to GND (Logic ZERO) or left open (Logic ONE). Status of these Address pins should match with status of address pins in the receiver for the transmission of the data. Data will be transmitted only when the Transmit Enable pin (TE) is LOW. 1.1MΩ resistor will provide the necessary external resistance for the operation of the internal oscillator of HT12E.

This concludes the mounting of the transmitter circuit and, as it is possible to see, the occupied space of the circuit is minimal so it should be possible to put it in a small box to be fixed to the most relevant dangers for visually handicapped people.

Step 3 - Receiver

In this step we shall approach the mounting of the receiver circuit that will receive and interpret the code sent by the transmitter. The next figures depicts this circuit with aid from the receiver’s datasheet.

Taking into account the use of an encoder on the transmitter circuit, it is now mandatory to have an appropriate decoder in the receiver circuit. The chosen decoder is the HT12D.

HT12D decoder will convert the received serial data to 4 bit parallel data D0 – D3. The status of these address pins A0-A7 should match with status of address pin in the HT12E at the transmitter for the transmission of data. 51KΩ resistor will provide the necessary resistance required for the internal oscillator of the HT12D.

Step 4 - Receiver with signal power

After being able to send a specific code to the receiver, the only thing missing is the code validation and signal strength manipulation at the receiving end. For this purpose some more complex electronic components had to be used such as a HEF4011 NAND Gate with 4 NAND’s. Transistors were also required in order to boost the voltage or even to force a ground. The figures below represents the mounted circuit as well as its final breadboard mount appearance.

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