Help! Need Encoder & Decoder for 433Mhz RF - RC Groups
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Apr 21, 2013, 11:14 AM
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Help! Need Encoder & Decoder for 433Mhz RF


Hi all,
I need an 6 or 7 channel encoder and decoeder for 433MHz Wireless RF transmitter Urgently. Please can any one share the schamtics.
here some info :

TX Technical Specifications:


A. Working voltage: 3V~12V

B. Working current: max≤40mA (12V), min≤9mA(3V)

C. Resonance mode: sound wave resonance (SAW)

D. Modulation mode: ASK /OOK

E. Working frequency: 315MHz-433.92MHz, customized frequency is available.

F. Transmission power: 25mW (315MHz at 12V)

G. Frequency error: +150kHz (max)

H. Velocity: ≤10Kbps

I. Self-owned codes: negative


RX Technical Specifications:


A. Working voltage: 5.0VDC +0.5V

B. Working current:≤5.5mA (5.0VDC)

C. Working principle: single chip superregeneration receiving

D. Working method: OOK/ASK

E. Working frequency: 315MHz-433.92MHz, customized frequency is available.

F. Bandwidth: 2MHz (315MHz, having result from testing at lowing the sensitivity 3dBm)

G. Sensitivity: excel 100dBm (50Ω)

H. Transmitting velocity: <9.6Kbps (at 315MHz and -95dBm)
Thankyou
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Apr 21, 2013, 12:58 PM
Who let the dogs out?
Phil_G's Avatar
There was a similar thread some time ago [here]
Although strictly they should use manchester coding to ensure DC balance, I've used Radiometrix 433 modules on a simple indoor set and found that in practice they work fine on straight analogue PPM. Someone used the same idea on a head-tracker for FPV [LINK], my contribution (which is what he finally went with) starts on page 4. One day I'll get around to doing a proper balanced encoder for these. For 4 or 5 channels I used the excellent Bruce Abbott decoder, for 6 or 7 channels you'd have to come up with something else. Bruce outputs the channel pulses during the input sync so theres not enough time for 6 or 7.
An alternative is to save these modules for another project, and go with Deltang DSM2 modules [LINK] which work out of the box and would give a far superior result IMHO.

Cheers
Phil
Last edited by Phil_G; Apr 21, 2013 at 01:19 PM.
Apr 22, 2013, 07:33 PM
RC beginner
deltang is an excellent solution, for megabucks lottery winners. we are talking over a hundred dollars here for minimum setup. ill also mention from experience that particular uhf pair will get little more than a foot or two of range with standard ppm. as mentioned a balanced input like manchester will increase that by couple orders of magnitude. data rate and error detection/correction are critical too so we are talking a pic or avr micro on each end.
Apr 22, 2013, 09:10 PM
Registered User
Not sure what you mean by 6 channels, six relays or six servos?

The way I used these links was to use a standard RS232 UART. I sent a normal data byte followed by the same byte inverted. This made the data stream mostly balanced. Also by sending the data twice there was a bit of error checking.

I used an Atmel micro with a built in UART so the interface was very simple. I also used 8 relays so the input was 8 buttons and the output was 8 relay drivers. Each bit in the byte controlled one relay so I was only sending one byte of data.

If you were to encode each '1' as '10' and each '0' as '01' you can use a UART to send the data and have nearly Manchester encoding. For example a byte of '11000011' would be encoded as '10100101' and '01011010'

There is a difference between sending continuous data and packets. With continuous data the receiver has to be synced at the start of transmission and re-synced if sync is lost. With packets the receiver has to be synced every packet.

I used continuous data and when no button was pressed the data was '00000000' so the receiver UART had no trouble syncing. The code was very simple, read an 8 bit port and send the data to the UART. At the other end it was read the UART and put the data byte in an output port which controlled 8 power transistors to drive the 8 relays.

With a superhet receiver and 12 volts on the transmitter, the range on ground was several blocks, way more then you could see the robot.

Your picture shows a super regen receiver. They also can get good range. However these cheap transmitters and receivers have to have well designed antennas and a ground plane. The transmitter may not even oscillate without a ground plane.
Last edited by mjsas; Apr 22, 2013 at 09:23 PM.


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