Re: Using RF modules


Jan 14 8:05 AM

 


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#8376 Jan 14 8:05 AM

Hello, I've made use of an RF link my recent GPS disciplined nixie

clock project. Luckily I managed to get by with rf modules which

used no type of encoding or decoding, such as Manchester Encoding

for example.



It's crossed my mind that in the future only modules which do use

encoding will be available and so does anybody have any experieince

of handling that protocol. i've been tempted to just pick up a

couple of Holtek decoder/encoder chips but thats more hardware when

software is all that's needed.



So I thought I would ask here if anyone can perhaps point me to a

link or offer some advice on working with Biphase decoding.



My Project is at



www.members.aol.com/fixitsan/index.html



Incidentally, the new version is almost ready, and is for a 40pin

16F77, it generates 180Vdc using the PWM/A-D hardware as a buck

convertor arrangement and will be posted soon.



Thanks in advance

Chris



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#8377 Jan 14 11:01 AM

Interesting project. What radio rx and tx units did you use? I

didn't see it in your docs, sorry if I missed it.

--- In piclist@yahoogroups.com, "Chris" fixitsan@a...> wrote:

>

> Hello, I've made use of an RF link my recent GPS disciplined nixie

> clock project. Luckily I managed to get by with rf modules which

> used no type of encoding or decoding, such as Manchester Encoding

> for example.

>

> It's crossed my mind that in the future only modules which do use

> encoding will be available and so does anybody have any experieince

> of handling that protocol. i've been tempted to just pick up a

> couple of Holtek decoder/encoder chips but thats more hardware when

> software is all that's needed.

>

> So I thought I would ask here if anyone can perhaps point me to a

> link or offer some advice on working with Biphase decoding.

>

> My Project is at

>

> www.members.aol.com/fixitsan/index.html

>

> Incidentally, the new version is almost ready, and is for a 40pin

> 16F77, it generates 180Vdc using the PWM/A-D hardware as a buck

> convertor arrangement and will be posted soon.

>

> Thanks in advance

> Chris



----------------------------

#8378 Jan 14 1:15 PM

--- In piclist@yahoogroups.com, "Phil" phil1960us@y...> wrote: >

> Interesting project. What radio rx and tx units did you use? I

> didn't see it in your docs, sorry if I missed it.



Thanks

Not sure about the receiver because I got them off eBay, 20 for 4

pounds. My first guess was that they were FM and I bought a 433.92MHz

FM transmitter, they didn't work together, so I took a chance on them

being AM on-off keying (OOK) and was succesful when using one

Rfsolutions' 4 pin AM transmitters, type RTF4..



www.rfsolutions.co.uk and also RS stock them www.rswww.com

At RS they're listed as 310-9891 (and they list acompatible receiver)



On my reference page I point to another pair of units from Maplins

which work without encoding the signal.



Beleive it or not, I also had some success with a remote doorbell

unit.(2.50 pounds in a sale) I had to hack the serial_out signal

coming from the Holtek decoder chip, but that's what brought my

attention to Holtek products too.



A few things I've learned other than about the Manchester encoding -

FM modules will generally have a greater range and be more immune to

interference. Stay away from 418MHz, there's too much interference

from other band users. WHen you have come up with your final system

only power up the transmitter when you have data to send if it's an

FM device. With an AM system resort to inverting the signal if you

have to in order to restrict your modulation to only the times when

data is present - whilst working on this project I've come across a

few people who have left their systems powered up full-time, and then

subsequently found that their car alarm remote only worked when you

got really close to the car, due to the intereference !



Chris



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#8379 Jan 14 2:03 PM

thanks, I'm in the US so I'll look to other suppliers but there are

plenty.



Good advice on powering the xmitter. How are you powering it up? via

mosfet in series with the xmitter's Vcc? I'm going to do something

like that as my project is battery powered.

--- In piclist@yahoogroups.com, "Chris" fixitsan@a...> wrote:

>

> --- In piclist@yahoogroups.com, "Phil" phil1960us@y...> wrote:

> >

> > Interesting project. What radio rx and tx units did you use? I

> > didn't see it in your docs, sorry if I missed it.

>

> Thanks

> Not sure about the receiver because I got them off eBay, 20 for 4

> pounds. My first guess was that they were FM and I bought a 433.92MHz

> FM transmitter, they didn't work together, so I took a chance on them

> being AM on-off keying (OOK) and was succesful when using one

> Rfsolutions' 4 pin AM transmitters, type RTF4..

>

> www.rfsolutions.co.uk and also RS stock them www.rswww.com

> At RS they're listed as 310-9891 (and they list acompatible receiver)

>

> On my reference page I point to another pair of units from Maplins

> which work without encoding the signal.

>

> Beleive it or not, I also had some success with a remote doorbell

> unit.(2.50 pounds in a sale) I had to hack the serial_out signal

> coming from the Holtek decoder chip, but that's what brought my

> attention to Holtek products too.

>

> A few things I've learned other than about the Manchester encoding -

> FM modules will generally have a greater range and be more immune to

> interference. Stay away from 418MHz, there's too much interference

> from other band users. WHen you have come up with your final system

> only power up the transmitter when you have data to send if it's an

> FM device. With an AM system resort to inverting the signal if you

> have to in order to restrict your modulation to only the times when

> data is present - whilst working on this project I've come across a

> few people who have left their systems powered up full-time, and then

> subsequently found that their car alarm remote only worked when you

> got really close to the car, due to the intereference !

>

> Chris







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#8380 Jan 15 2:19 AM

--- In piclist@yahoogroups.com, "Phil" phil1960us@y...> wrote: >

> thanks, I'm in the US so I'll look to other suppliers but there are

> plenty.

>

> Good advice on powering the xmitter. How are you powering it up?

via > mosfet in series with the xmitter's Vcc? I'm going to do something

> like that as my project is battery powered.

>



I've got AM modules set up such that there is an RFoutput only when a

logic one is on the input. If I had FM modules I'ld probably switch

the ground side of the transmitter with a transistor. In my project

there's one pin which flips high about 20mS before data is due to be

sent and then drops low just after the last byte has gone out, but I

don't need to use it with AM. If you're going to switch the

transmitter like this have a look at the datasheet which you get for

your modules and make a turn-on delay long enough to match the

transmitter's warm-up time, some modern transmitters come with an

enable line which lets you switch to transmit mode faster still.



Chris


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