DIY remote control based on PIC

transmitter	receiver
8-channel 4-channel ON/OFF	8-channel 4-channel
	output ch# type state K1 L M   K2 L M   K3 L M   K4 L M   K5 L M   K6 L M   K7 L M   K8 L M

Control up to 8 devices by this easy constructable remote control. It can work as a radio or infrared remote control, depending on the components. Each device output can be configured to be momentary (turned on while you press the button) or latched. Latched outputs can be toggled on/off by one button per channel, or turned on and off by two buttons per channel.

Try it out now! Click on the transmitter buttons and see how the receiver outputs change. Change transmitter or receiver version. Alter the receiver output type.

Containing a PIC microcontroller, the circuit is very flexible. You can decide which receiver outputs are latched and which are momentary. The Manchester-coded transmitter output is well suited for the cheapest ASK radio modules or for infrared control. The units are configurable to a unique address, which must match to control the devices.

If you have trouble with programming PIC microcontrollers, you can consider builing other circuits based on Holtek HT-12D, HT-12E and Motorola MC145026, MC145027, MC145028 encoders/decoders.

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The difference between the 4-channel and the 8-channel version is only the software inside. The 8-channel transmitter has one button (S1-S8) per channel. The 4-channel transmitter uses S1-S4 buttons to turn on, S5-S8 buttons to turn off channel 1-4 (use with latched outputs on the receiver). The D1-D4 diodes and J1-J4 jumpers are optional, and are used to setup the transmitter address. V+ supply voltage should be between 2.5-5.5VDC. It is practical to use two or three AAA batteries.

Download the code for

• 4-channel IR transmitter
• 8-channel IR transmitter

The difference between the 4-channel and the 8-channel version is only the software inside. The 8-channel receiver outputs are individually configurable for latched or momentary output. The 4-channel receiver has two outputs per channel: K1-K4 are latched outputs, K5-K8 are momentary outputs for the four channels. The "valid" LED shows the transmitter activity. Make sure to turn on all address jumpers when the transmitter diodes are absent, or the J1-J4 jumpers are cut. Choose V+ supply voltage between +6-15VDC, based on the relay voltage ratings. For 6V relays, use +6VDC, for 12V relays use +12VDC.

please observe the corresponding address configuration!
transmitter: no diodes connected	receiver: switches all ON
transmitter: all diodes connected	receiver: switches all OFF

Download the code for

• 4-channel RF receiver
• 8-channel RF receiver

Zoom the picture

The difference between the 4-channel and the 8-channel version is only the software inside. The 8-channel receiver outputs are individually configurable for latched or momentary output. The 4-channel receiver has two outputs per channel: K1-K4 are latched outputs, K5-K8 are momentary outputs for the four channels. The "valid" LED shows the transmitter activity. Make sure to turn on all address jumpers when the transmitter diodes are absent, or the J1-J4 jumpers are cut. Choose V+ supply voltage between +6-15VDC, based on the relay voltage ratings. For 6V relays, use +6VDC, for 12V relays use +12VDC.

please observe the corresponding address configuration!
transmitter: no diodes connected	receiver: switches all ON
transmitter: all diodes connected	receiver: switches all OFF

Download the code for

• 4-channel IR receiver
• 8-channel IR receiver

Zoom the picture

All the devices use new, FLASH-based microcontrollers, this means that they can be re-programmed many times. You can experiment with the source code settings to fit your needs. The code must be compiled as a linked project under MPLAB. Please check FAQ at the PIC page.

source file	line	meaning
enc-042.asm	25 #define MODE_CH4	the device is 4-channel, sending ON/OFF channel codes
enc-042.asm	28 #define MODE_CH8	the device is 8-channel, sending simple codes for channels
irmtxv4.asm	44 pwm_freq EQU d'38000'	the IR transmitter frequency is set to 38000 Hz. This should match the receiver module frequency
dec-043.asm	36 LATCH_MASK EQU 0xff	select outputs to be latched. This is a binary mask, one bit per channel. Other channels will be momentary Example: LATCH_MASK EQU B'00001111' # channel 1-4 are latched, channel 5-8 are momentary
dec-044.asm	38 LATCH_MASK EQU 0xff
mrxv4.asm	56 #define SKL btfsc 57 #define SKH btfss	normal decoder logic input is used for the RF receivers (most times)
mrxv4.asm	60 #define SKL btfss 61#define SKH btfsc	inverse decoder logic input is used for the IR receivers (most times)

The radio version circuit diagrams show generic ISM RF modules, which connect to the circuits using two power pins and one modulation pin. The transmitter (TX) module is connected to the transmitter circuit. The receiver (RX) module is connected to the receiver circuit. Choose ISM RF modules from the list of modules. The remote control works with the cheapest OOK/ASK modules and with FSK modules, too. Use the same frequency and modulation type for all modules.

If you are building the infrared version, choose an IR LED matching the wavelength of the receiver module. The receiver center frequency should match the transmitter modulation frequency, which can be set the transmitter source (pwm_freq). If in doubt, just choose a TSOP1738. A list of usable modules: Sharp GP1U52X, IS1U60L, Vishay TSOP17XX, TSOP18XX.

Q: Do I have to use the same transistor in the receiver?
A: You can use other logic N-channel mosfets or npn bipolar transistors (with a series base resistor added) to drive the relays in place of Q1-Q8 of the remote control receiver. Examples: bs170, bc182+2.2kohm

Q: How do I set toggle or momentary mode for the relays?
A: Make a modification in the receiver source code. Modify the LATCH_MASK define - this contains one bit for every channel. A zero bit sets the corresponding output to momentary, a high bit sets the corresponding output to latched. For example, the line LATCH_MASK EQU B'00001111' sets channels 8-5 to momentary and channels 4-1 to latched (toggle) mode. Then use the compiler (MPLAB or gputils) to assemble the code.

• list of ISM RF modules
• TSOP17XX infrared receiver IC datasheet
• General info about PIC microcontrollers and their programming
• Microchip PIC16f630 PIC16f684 PIC16f628 microcontroller datasheet
• Microchip MPLAB development environment for the PIC devices
• GNU tools for PIC development
• mc145026 mc145027 mc145028 datasheet