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Designing RF Remote Controls

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Designing RF Remote Controls
Radio-frequency remote controls are inevitable and are appearing in great numbers with better user experience. They control audio, video and other electronic equipment like video games, stereo systems and lighting controls. They are also responsible for home automation including garage door openers, air conditioning units, fans and automobiles with remote keyless entry (RKE) key fobs. They have overcome the drawbacks of infrared (IR) remotes including line-of-sight pointing, short transmission range, reflection problems and high power consumption of IR LEDs leading to low battery life. The basic components needed to design an RF remote control are: buttons for user inputs, a microcontroller unit (MCU) to act upon user inputs, an RF transmitter to transmit the message, an antenna, and a battery.
There are three challenges designers face in designing RF remote controls: long battery life, low costs and providing consistent maximum transmission range.  To solve these challenges, many integrated, single-chip RF solutions such as System-on-chip (SoC) transmitters have come up that require less external components and reduce BOM cost. They provide features like ultra-low-power and wake-on-touch operations to enhance battery life. Many transmitters provide antenna tuning feature that eliminates the tedious RF matching problem and reduces RF design time, thereby improving time-to-market. A library of useful remote control functions such as button press routines and battery monitoring help reduce code size and speed up development.  Automatic capacitor adjustments maximize the transmit power of the remote control by fine-tuning the antenna when there is interference from the user’s hand. All these features are successful in closing the RF-IR price gap and overcoming problems with traditional transmitters. Let’s walk through reference designs of some RF remotes that meet these design challenges and are available with complete documentation.
  • Cost-effective 2-Way RF Remote Control: This reference design targets a low-cost, low-BOM-count 2-way Remote Control (RC) design for the industrial/scientific/medical  (ISM) band. The 2-way RC boards provide a switch input and three LEDs for human interaction. The compact board of 3cm x 3cm form factor contains a transceiver with the radio, microcontroller, a small antenna mounting connector, and multiple ports to connect various inputs to the system. This board can be operated from any 3V power source. The board is built around a MAX7032 radio transceiver IC and the MAXQ610 microcontroller from Maxim Integrated. The microcontroller comes preprogrammed to operate as the 2-way remote control. It can also be programmed by the user with JTAG interface. This document includes the complete documentation such as Gerber files, schematic and layout files. More on this Reference Design
  • RF Remote Control not limited by Line-of-Sight: This reference design can implement a one-way or two-way RF based remote control that is not limited by line-of-sight conditions. Operating in the worldwide 2.4GHz ISM band, the remote control unit consists of the RF module and application board. The RF module performs major functions like key scan, LED status update and communication over SPI and UART with the help of ATmega88 MCU and radio IC. It includes major components like the nRF24L01 radio IC, antenna, matching network, crystal and microcontroller. The USB receive dongle is plugged into a PC and uses a nRF24L01 IC with same components as are present on the RF module. The USB interface uses the C8051F321 IC to receive the remote control signals. The application board contains RF module footprint, battery and connectors for redesign based on different form-factors of end-products. The reference design consists of complete design files (schematics, layout, Gerber, BOM data and source code) for a USB receive dongle, an RF module and, an application board. More on this Reference Design
  • Advanced RF Remote Control: This reference design can be used for the development of robust remote-control systems with low bill-of-material cost for use in consumer electronics and electronic shelf labeling. The design utilizes a CC2533 from Texas Instruments, an optimized system-on-chip (SoC) solution for low-cost implementation and also provides an SPI/UART/I2C interface for implementing the remote-control system. The CC2533 combines an excellent RF transceiver with a 8051 compliant CPU with many powerful features like ultra-low-power consumption. The CC2533 also includes example software to implement a remote control system. More on this Reference Design
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