Summary of 64 KEY INFRARED REMOTE CONTROLLER USING PT2222M – NEC CODE
This article details a 64-channel Infra-Red Remote Transmitter circuit built around the PT2222M IC. Operating on 2V to 3.3V, it supports NEC transmission format for devices like TVs and air conditioners. The system allows up to 65,536 custom codes via external diodes and resistors, handles single and double key inputs with collision prevention, and features a fast response time of 126 ms intervals. It is suitable for robotics, audio equipment, and home automation applications.
Parts used in the 64 Channels Infra-Red Remote Transmitter:
- PT2222M IC
- External Diodes
- Resistors
- J1 Jumper
- On board Jumper
- PCB
64 channels Infra-Red Remote Transmitter circuit build around PT2222M IC, The IC is pin to pin compatible with NEC uPD6122 respectively, the remote is capable of controlling 64 functions keys and 3 double keys. The PT2222M Infra-red remote control transmission ICs using the NEC transmission format that is ideally suited for TVs, DVD Players, Audio Equipment, Air Condition, etc. By combining external diode and resistors, maximum of 65536 custom codes can be specified. The NEC transmission format consists of leader codes, custom codes (16 Bits), and data codes (16 Bits). It can be used for various systems through decoding by a microcontroller.
FEATURES
- Low Voltage 2V To 3.3V
- Low Current dissipation: 1uA Max (Standby)
- Custom Codes: 65536 (Set by optional provided diodes and resistors)
- 64 Codes (Single Input) , 3 Codes ( Double Input) , Expandable up to 128 Codes through J1 Jumper
APPLICATION
- Audio Equipment
- TV
- Cable TV
- Air Condition
- DVD Player
- Robotics
Key input pins (KI0 to KI7), key input/output pins (KI/O0 to KI/O7)
When several keys are pressed simultaneously, the transmission of the corresponding signals is inhibited by a multiple-input prevention circuit. In the case of double-key input, transmission is inhibited if both keys are pressed simultaneously (within 36 ms interval); if not pressed simultaneously, the priority of transmission is first key, then second key. When a key is pressed, the custom code and data code reading is initiated, and 36 ms later, output to REM output is initiated. Thus if the key is pressed during the initial 36 ms, one transmission is performed. If a key is kept pressed for 108 ms or longer, only leader codes are consecutively transmitted until the key is released. Keys can be operated intermittently at intervals as short as 126 ms (interval between two on’s), making this an extremely fast-response system.
- The REM output pin outputs the transmission code, which consists of the leader code, custom code (16 bits), and data code (16 bits)
- By controlling D7 of the data code with this pin, the PT2222M can transmit 64 and 128 different data codes, respectively. By connecting the SEL pin to VDD or VSS via on board Jumper , D7 is set to “0” or “1”, respectively.
- By placing a diode between the CCS pin and the KI/O pin, it is possible to set a custom code. When a diode is connected, the corresponding custom code is “1”, and when not connected, it is “0”.
- The LMP pin outputs a low-level signal while the REM pin outputs a transmission code.
SCHEMATIC
PARTS LIST
PHOTOS
VIDEO
PCB
Source: 64 KEY INFRARED REMOTE CONTROLLER USING PT2222M – NEC CODE
- What voltage range does the PT2222M operate on?
The IC operates at a low voltage range of 2V to 3.3V. - How many custom codes can be specified using this circuit?
A maximum of 65536 custom codes can be specified by combining external diodes and resistors. - Can multiple keys be pressed simultaneously without issues?
No, a multiple-input prevention circuit inhibits signal transmission when several keys are pressed simultaneously. - What happens if a key is held down for longer than 108 ms?
Only leader codes are consecutively transmitted until the key is released. - How is the D7 bit of the data code configured?
D7 is set to 0 or 1 by connecting the SEL pin to VDD or VSS via an on-board jumper. - How do you set a specific custom code value?
Placing a diode between the CCS pin and the KI/O pin sets the corresponding custom code to 1, while no connection sets it to 0. - What is the minimum interval allowed for intermittent key operation?
Keys can be operated intermittently at intervals as short as 126 ms. - Which components are required to achieve 128 expandable codes?
Expanding up to 128 codes requires the use of the J1 Jumper along with the standard configuration.
