FM Remote Encoder/Decoder Circuit

In the post RF Remote Control Circuit for Home Appliances, we looked at how to control home appliances using radio frequency communication. Let’s look at how to use the RF600E and RF600D ICs to create an FM remote encoder and decoder circuit. The communication is established with high degree security using this pair of encoder and decoder ICs. These ICs operate between 2 and 6.6 volts DC.

For transmission, this system uses FM (Frequency Modulation). When you press a push button, a code is created in the transmission part. An encoder is employed to convert parallel data to serial data in this case. The FM Tx module receives this serial data and transmits it. The serial data is received by the FM Rx module and supplied to the decoder, which produces the appropriate output.

Outline

• FM Remote Encoder and Decoder Circuit Diagram:
  • Transmitter Section:
  • Receiver Section:
  • FM Remote Encoder/Decoder Circuit Design:
    • Transmitter Section:
    • Receiver Section:
  • How to Operate FM Remote Encoder and Decoder Circuit?
  • FM Remote Encoder/Decoder Circuit Advantages:
  • FM Remote Encoder/Decoder Circuit Applications:
    • Circuit Limitation:

FM Remote Encoder and Decoder Circuit Diagram:

Transmitter Section:

Circuit Components:

• RF600E encoder
• FM Transmitter module
• 4 push buttons
• Bc848 Transistor
• Led
•  Resistors – 2.2k, 10k

Receiver Section:

Circuit Components:

• RF600D Decoder
• FM Receiver module
• Slide switch
• Push button
• Red LED
• Resistors – 1k(2), 15k, 22k

FM Remote Encoder/Decoder Circuit Design:

The circuit mainly consists of two sections, one is Transmitter section used t transmit the remote data and other is Receiver section used to receive the data.

Transmitter Section:

The RF600E encoder, FM transmitter module, four switches, and LED are all found in this area. The parallel data is generated using four push buttons. When you press a push button, the encoder’s 6th pin generates the corresponding code. The signal transmission is indicated by the LED, which is attached to the encoder’s 7th pin.

RF600E Encoder:

The balanced Manchestar encoded data protocol is used for transmission by this pair of encoder and decoder ICs. To use this encoder IC as a transmitter, you only need a few more components. There is no need for human involvement because the transmission is automatic.

A preamble, header, encrypted data, and a CRC bit are all included in the data format. The packet size is 67 bits in this case.

Low Battery Warning:

For each action, this encoder IC reads the battery status. The flag bit is sent to the decoder IC if the voltage is less than 3.8 volts.

Pin Configuration:

PIN NO.	NAME	DESCRIPTION
1	S0	Input data pin0
2	S1	Input data pin1
3	S2	Input data pin2
4	S3	Input data pin3
5	Vss	Ground reference connection
6	OP	Data output pin
7	LED	Cathode connection for driving LED during the transmission
8	Vcc	Supply voltage pin

Receiver Section:

The RF600D decoder and its accompanying components make up the receiver section. The digital output pins 17, 18, 1, and 2 correspond to the input switches. When you press a push button, the decoder’s corresponding pin goes low. The SPDT switch is used to select whether the digital function is latching or memory. The learn switch is used to activate the learn mode on the decoder IC.

Decoder RF600D:

Protocol data is sent serially as a stream of ASCII characters with a baud rate of 9600 bits per second in this RF chipset. When it comes to the frame format, there are eight data bits and one stop bit.

Pin Configuration:

PIN NO.	NAME	INPUT/OUTPUT	DESCRIPTION
1	OP3	Out	Data output pin
2	OP4	Out	Data output pin
3	LB	Out	Pin goes low, when battery is low
4	Vcc	In	Supply voltage pin
5	Vss	In	Ground pin
6	ECS	Out	Connected to EEPROM CS pin
7	ECLK	Out	Connected to EEPROM CLK pin
8	EDAT	I/0	connected to EEPROM DATA PIN
9	IN	In	Data input
10	LRN	In	learn/erase switch and status LED drive
11	SD1	Out	serial data output
12	LKIN	In	Option Link Input for Momentary or Latched outputs
13	SLEEP	In	1 = Run, 0 = Sleep Mode
14	Vcc	In	Positive supply voltage pin
15	Unused	N/A	no connection
16	Unused	N/A	no connection
17	OP1	Out	Data output pin
18	OP2	Out	Data output pin

How to Operate FM Remote Encoder and Decoder Circuit?

1. Give the connections as per the circuit diagram.
2. Connect the LED’s at the decoder outputs.
3. Apply 5V supply to the both transmitter and receiver sections.
4. Initially all the LED’s will glow.
5. Now press the first button at transmitter section, you can observe that first LED will off at decoder section. In the same way for each switch at transmitter the corresponding LED at receiver will off.
6. Switch off the power supply for both transmitter and receiver sections.

FM Remote Encoder/Decoder Circuit Advantages:

1. Stand alone operation
2. LED indication of signal transmission
3. Battery low indication
4. Manchester modulation
5. Sleep mode.

FM Remote Encoder/Decoder Circuit Applications:

• Used in general purpose Remote control applications
• Used in burglar alarm systems
• used in automotive systems
• Used in Electronic door locks

Circuit Limitation:

• This circuit is theoretical and may require some practical changes.