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RX/TX modules

J

Jason S

Jan 1, 1970
0
Hi,

I would like to know more about RF Transmitters/Receivers to provide
wireless communications from one low voltage device to another related low
voltage device (ideally 6-12V). I've looking around on the internet but I'm
still a little stuck.

In the past, I've been cheating by purchasing those ready-made remote
control switches and hard-wiring my existing circuits to the remote control
(as in Keyfob transmitter!) and receiver. Has been working ok, but I want
to do it properly now! No keyfobs!

I have seen various **RX and TX "modules"** out in the market, but someone
said you can't just connect them directly to a power source and antenna and
expect them to work... I need a driver or something... not sure exactly what
he called it... Decoder maybe?
I've noticed a lot of the suppliers make it a little off-putting by not
providing links for compatible drivers - especially for amateurs like
myself. I mean, how do I know which driver to get for the RX/TX modules I
decide to get?

For argument's sake, let's just say I decide to purchase the "433MHz
Wireless Modules" from Jaycar Electronics (ZW-3100 and ZW-3102). What
driver circuits will work with these modules, and please explain to me why
you chose them.

Can anyone point me in the right direction?

Thanks in advance,

Jason.
 
D

David L. Jones

Jan 1, 1970
0
Jason said:
Hi,

I would like to know more about RF Transmitters/Receivers to provide
wireless communications from one low voltage device to another related low
voltage device (ideally 6-12V). I've looking around on the internet but I'm
still a little stuck.

In the past, I've been cheating by purchasing those ready-made remote
control switches and hard-wiring my existing circuits to the remote control
(as in Keyfob transmitter!) and receiver. Has been working ok, but I want
to do it properly now! No keyfobs!

I have seen various **RX and TX "modules"** out in the market, but someone
said you can't just connect them directly to a power source and antenna and
expect them to work... I need a driver or something... not sure exactly what
he called it... Decoder maybe?
I've noticed a lot of the suppliers make it a little off-putting by not
providing links for compatible drivers - especially for amateurs like
myself. I mean, how do I know which driver to get for the RX/TX modules I
decide to get?

For argument's sake, let's just say I decide to purchase the "433MHz
Wireless Modules" from Jaycar Electronics (ZW-3100 and ZW-3102). What
driver circuits will work with these modules, and please explain to me why
you chose them.

Can anyone point me in the right direction?

Most of these ready made RF modules are transparent serial in-out
devices. If you feed a digital serial data stream in at one end, it
comes out the other end, no need for any other "driver".
Usually you'd have a microcontroller at either end and you communicate
from micro to micro using the internal USART, so I guess you could call
the micro the "driver". The micros don't know the difference between
hard wiring together or running through these RF modules, they are just
transmitting and receiving serial digital data.

For example, lets say you had 5 digital inputs and you wanted to
trasmit these digital signals to a reciever at the other end to control
5 LEDs or whatever. You could use a PICAXE chip at the input end which
scans the 5 inputs and sends a unique byte to the transmitter for each
input saying if it's HIGH or LOW. Another PICAXE at the receiving end
decodes this serial data sets the 5 outputs HIGH or LOW as required.

Hope that helps.

Dave :)
 
J

Jason S

Jan 1, 1970
0
David L. Jones said:
Most of these ready made RF modules are transparent serial in-out
devices. If you feed a digital serial data stream in at one end, it
comes out the other end, no need for any other "driver".
Usually you'd have a microcontroller at either end and you communicate
from micro to micro using the internal USART, so I guess you could call
the micro the "driver". The micros don't know the difference between
hard wiring together or running through these RF modules, they are just
transmitting and receiving serial digital data.

For example, lets say you had 5 digital inputs and you wanted to
trasmit these digital signals to a reciever at the other end to control
5 LEDs or whatever. You could use a PICAXE chip at the input end which
scans the 5 inputs and sends a unique byte to the transmitter for each
input saying if it's HIGH or LOW. Another PICAXE at the receiving end
decodes this serial data sets the 5 outputs HIGH or LOW as required.

Hope that helps.

Dave :)


Thanks Dave for the info.
I sorta get what you are trying to say. I looked up PICAXE on the net
(www.picaxe.co.uk) briefly and can see these chips are programmable I/O
chips... looks relatively easy, even for some of my other apps.

Am I on the right track here? (block diagram) :
Digital signals > Picaxe > TX Data Pin(Out) ~ ~ ~ Transmission ~ ~ ~ RX
Data Pin(In) > Picaxe > Outputs.

What if I only have 1 digital input that I want to transmit to the receiver
at the other end? Would I still need a chip like the Picaxe on either end,
or not?

Regards,
Jason.
 
D

David L. Jones

Jan 1, 1970
0
Jason said:
Thanks Dave for the info.
I sorta get what you are trying to say. I looked up PICAXE on the net
(www.picaxe.co.uk) briefly and can see these chips are programmable I/O
chips... looks relatively easy, even for some of my other apps.

Yep, they are an easily programmable microcontroller.
Perfect for a job such as this.
Am I on the right track here? (block diagram) :
Digital signals > Picaxe > TX Data Pin(Out) ~ ~ ~ Transmission ~ ~ ~ RX
Data Pin(In) > Picaxe > Outputs.

Correct, that's all you do.
What if I only have 1 digital input that I want to transmit to the receiver
at the other end? Would I still need a chip like the Picaxe on either end,
or not?

Most likely you still need the PICAXE or some other microcontroller.
Most RF modules are designed for a serial input, so need a minimum
input "data rate" like 300baud. You can probably get modules that have
digital level inputs though.

Dave :)
 
J

Jason S

Jan 1, 1970
0
David L. Jones said:
Yep, they are an easily programmable microcontroller.
Perfect for a job such as this.


Correct, that's all you do.


Most likely you still need the PICAXE or some other microcontroller.
Most RF modules are designed for a serial input, so need a minimum
input "data rate" like 300baud. You can probably get modules that have
digital level inputs though.

Dave :)


Cool! I shall see how I go. It's great to know that these chips also come
in different sizes (8/18/28/40pin)!

Thanks again Dave.

Regards,
Jason.
 
D

David L. Jones

Jan 1, 1970
0
Jason said:
Cool! I shall see how I go. It's great to know that these chips also come
in different sizes (8/18/28/40pin)!

Silicon Chip have a regular PICAXE column and lots of good PICAXE
projects, worth following.

Once you've mastered PICAXE's you can step up to regular
microcontrollers like PIC or Atmel AVR programmed in BASIC, C or even
assembler.

Also, as I mentioned in another thread, I think there is even a PICAXE
uses group based in Sydney that meets every month.

Have fun!

Dave :)
 
B

bigtom28

Jan 1, 1970
0
David L. Jones said:
Silicon Chip have a regular PICAXE column and lots of good PICAXE
projects, worth following.

Once you've mastered PICAXE's you can step up to regular
microcontrollers like PIC or Atmel AVR programmed in BASIC, C or even
assembler.

Also, as I mentioned in another thread, I think there is even a PICAXE
uses group based in Sydney that meets every month.

Have fun!

Dave :)

Much appreciated Dave. I'm gonna have fun with this! I've never used
microcontrollers before, and these sound pretty simple enough. I shall have
a look at that Silicon Chip column too.

Regards,
Jason.
 
J

Jason S

Jan 1, 1970
0
David L. Jones said:
Silicon Chip have a regular PICAXE column and lots of good PICAXE
projects, worth following.

Once you've mastered PICAXE's you can step up to regular
microcontrollers like PIC or Atmel AVR programmed in BASIC, C or even
assembler.

Also, as I mentioned in another thread, I think there is even a PICAXE
uses group based in Sydney that meets every month.

Have fun!

Dave :)


Oh just one for question Dave. I've seen some example schematics of how
those TX/RX are connected (typically), and they are connected to Encoder and
Decoder IC's. Would I need to sandwich these in between the PICAXE and the
Module, or no need?
PICAXE>Encoder>TXmodule ~~~Transmission~~~ RXmodule>Decoder>PICAXE ???
I'm sorta guessing that it would depend on how reliable I want the
transmission, i.e. noise/interference elimination? Would I be correct to
assume this?

Jason.
 
L

Lionel

Jan 1, 1970
0
Oh just one for question Dave. I've seen some example schematics of how
those TX/RX are connected (typically), and they are connected to Encoder and
Decoder IC's. Would I need to sandwich these in between the PICAXE and the
Module, or no need?

No need. One of the big reasons to use a little micro like the Picaxe
in this kind of device is that you can program it to do all that for
you.

PICAXE>Encoder>TXmodule ~~~Transmission~~~ RXmodule>Decoder>PICAXE ???
I'm sorta guessing that it would depend on how reliable I want the
transmission, i.e. noise/interference elimination? Would I be correct to
assume this?

No. Most serial<->parallel chips don't do error checking, & it's much
easier to add code for parity (or checksumming, ECC, etc) checking
into your program than it is to do it in hardware anyway.

And best of luck with learning the PICAXE, or whatever chip you end up
going with. Once you get over the initial learning hump, designing
with embedded controllers is a lot of fun, so don't get discouraged if
you find it a struggle at first. ;)
 
D

David L. Jones

Jan 1, 1970
0
Jason said:
Oh just one for question Dave. I've seen some example schematics of how
those TX/RX are connected (typically), and they are connected to Encoder and
Decoder IC's. Would I need to sandwich these in between the PICAXE and the
Module, or no need?

No need if the RF module accepts direct serial input, it already has
the "encoder/decoder" inbuilt, or simply doesn't need one. There are RF
modules that will not accept a direct digital input and they are more
difficult to use. The Jaycar ones will accept digital digital input
judging from it having a specification for a certain data rate, but
check the data sheet to be sure.
PICAXE>Encoder>TXmodule ~~~Transmission~~~ RXmodule>Decoder>PICAXE ???
I'm sorta guessing that it would depend on how reliable I want the
transmission, i.e. noise/interference elimination? Would I be correct to
assume this?

If you want error correction/detection then you'll have to do this in
the PIC. More advanced units like wirless RS232 modules will have their
own inbuilt error checking. Open one up though and you'll find a
microcontroller stuck on the front end of a standard RF module!
Basic error detection would use simple parity checking, or you could
simply send the same byte say 3 times in row. If the receiver micro
does not get 3 bytes the same then it simply discards the data.

Dave :)
 
J

jasen

Jan 1, 1970
0
For argument's sake, let's just say I decide to purchase the "433MHz
Wireless Modules" from Jaycar Electronics (ZW-3100 and ZW-3102). What
driver circuits will work with these modules, and please explain to me why
you chose them.

I'd go with small microcontrollers and connect the devices to the serial
port. i don't know of anyone that sells loose code emitters or detectors.

how would I choose:

look at the voltages it needs on the input and produces on the output
choose something that can produce and something that can recognise a coded signal
and connect them to the input of the transmitter or the output of the
receiver respectively.

Bye.
Jasen
 
J

jasen

Jan 1, 1970
0
Am I on the right track here? (block diagram) :
Digital signals > Picaxe > TX Data Pin(Out) ~ ~ ~ Transmission ~ ~ ~ RX
Data Pin(In) > Picaxe > Outputs.

What if I only have 1 digital input that I want to transmit to the receiver
at the other end? Would I still need a chip like the Picaxe on either end,
or not?

If you want the receiver end recognise your transmitter then yes you will,
the receiver module will produce an output signal whenever it sees anything
transmitting on 455Mhz, so you need to make the signal from your transmitter
distinctive and make the receiver end discriminate between that signal and
someone elses keyfob.


Bye.
Jasen
 
J

Jason S

Jan 1, 1970
0
David L. Jones said:
No need if the RF module accepts direct serial input, it already has
the "encoder/decoder" inbuilt, or simply doesn't need one. There are RF
modules that will not accept a direct digital input and they are more
difficult to use. The Jaycar ones will accept digital digital input
judging from it having a specification for a certain data rate, but
check the data sheet to be sure.


If you want error correction/detection then you'll have to do this in
the PIC. More advanced units like wirless RS232 modules will have their
own inbuilt error checking. Open one up though and you'll find a
microcontroller stuck on the front end of a standard RF module!
Basic error detection would use simple parity checking, or you could
simply send the same byte say 3 times in row. If the receiver micro
does not get 3 bytes the same then it simply discards the data.

Dave :)

Thanks again!
 
J

Jason S

Jan 1, 1970
0
Lionel said:
No need. One of the big reasons to use a little micro like the Picaxe
in this kind of device is that you can program it to do all that for
you.



No. Most serial<->parallel chips don't do error checking, & it's much
easier to add code for parity (or checksumming, ECC, etc) checking
into your program than it is to do it in hardware anyway.

And best of luck with learning the PICAXE, or whatever chip you end up
going with. Once you get over the initial learning hump, designing
with embedded controllers is a lot of fun, so don't get discouraged if
you find it a struggle at first. ;)
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

Thanks Lionel!
 
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