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Data Transfer & frequency question?

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shaneshane1

New Member
just wondering if anyone knows of any good tutorials on this subject or if anyone could give me some help trying to understand this topic a little better?

Basically what i am trying to find out is, how is "data" transfered across a frequency?

does data travel across an existing frequency or does the frequency only exist when there is data to be sent?

Example: I set up a IR transmitter @ 38KHz and sent that signal to a receiver with a LED on the output!(the LED just stays lit because the signal is so fast) would i be right in saying that there was no "data" sent to the receiver, just a 38KHz signal?

And when i use a TV remote @ 38KHz the LED flashes on and off very fast! would this indicate that "data" is been sent?


I know that "data" is 1'ns(high) and 0's(low) but isn't the frequency also 1'ns and 0's, how can you send "data" along a frequency if they both have 1'ns and 0's?

sorry there is so many questions its just i cant work it all out without some sort of human interaction!
 

Roff

Well-Known Member
Here is a descripton of how a TV remote works. Note that when the LED is on, it is modulated (turned on and off) at a 38kHz rate.
 

shaneshane1

New Member
Roff said:
Here is a descripton of how a TV remote works. Note that when the LED is on, it is modulated (turned on and off) at a 38kHz rate.

Thanks, that's starting to make a little more sense now, i bookmarked that page :D
 

crutschow

Well-Known Member
Most Helpful Member
Basically it's the variation in the frequency, pulse width, or amplitude of the sent wave that carries the data. As you thought, a steady frequency carries no information. Some transmission schemes send a steady frequency (carrier) even when no information is being sent. This is typical of standard AM and FM radio signals. Others, such as most IR remotes, send a signal only when data is being sent.
 

shaneshane1

New Member
crutschow said:
Basically it's the variation in the frequency, pulse width, or amplitude of the sent wave that carries the data. As you thought, a steady frequency carries no information. Some transmission schemes send a steady frequency (carrier) even when no information is being sent. This is typical of standard AM and FM radio signals. Others, such as most IR remotes, send a signal only when data is being sent.

Thanks!!!

So in the IR situation, if i was to send a code of data eg: 1011001, how does it send the two 1ns and two 0's that are right next to each other without sending a 0 in between them?

Does the code of data do the "101" part and then turn off and then turn back on again and do the "10" and then off and on and then do the "01" very fast?

So 101 (then no signal) 10 (then no signal) 01 then code done, repeat

101 10 01 101 10 01 101 10 01 and so on as the button is held down?


sorry if it isn't clear to understand, i don't know of any other way to explain what i am thinking.
 

shaneshane1

New Member
Thanks for the link bill, there just one thing i don't understand about it!

The logic "0's" and bursts have the same times, 0.6ms?, so what are the bursts?

are they the times there is no signal been sent at all?

How can you send a 0? isn't a 0 just when there is no signal(low)?
 

Roff

Well-Known Member
shaneshane1 said:
Thanks for the link bill, there just one thing i don't understand about it!

The logic "0's" and bursts have the same times, 0.6ms?, so what are the bursts?

are they the times there is no signal been sent at all?

How can you send a 0? isn't a 0 just when there is no signal(low)?
A "1" is transmitted when the LED is switched on and off for 1.2mS at a 38kHz rate. A logic 0 is transmitted when the LED is switched on and off for 0.6mS at a 38kHz rate. There is a dead time between bits of 0.6mS, when the LED is off. This graph is on the page you bookmarked, but you apparently didn't understand it. :confused:



5262-princi2.gif
 

shaneshane1

New Member
Roff said:
A "1" is transmitted when the LED is switched on and off for 1.2mS at a 38kHz rate. A logic 0 is transmitted when the LED is switched on and off for 0.6mS at a 38kHz rate. There is a dead time between bits of 0.6mS, when the LED is off. This graph is on the page you bookmarked, but you apparently didn't understand it. :confused:

Thanks roff, well correct me if i am wrong please, but the way i see it is a "0" is still a "1"(high) but for a shorter period of time?

and the dead time is the tail end of that shorter "1" representing the "0"(low) part?

Sorry if this makes no sense, but this is the way i see it.
 

Roff

Well-Known Member
shaneshane1 said:
Thanks roff, well correct me if i am wrong please, but the way i see it is a "0" is still a "1"(high) but for a shorter period of time?

and the dead time is the tail end of that shorter "1" representing the "0"(low) part?

Sorry if this makes no sense, but this is the way i see it.
You are confusing a high voltage with a "1". Ones and zeroes can be represented by anything:
0=apple
1=banana

or,

0=red
1=black

or, in the case we are discussing,

0=38kHz for 0.6mS
1=38kHz for 1.2mS
with 0.6mS of dead time between successive bits.
 
Last edited:

shaneshane1

New Member
Roff said:
You are confusing a high voltage with a "1". Ones and zeroes can be represented by anything:
0=apple
1=banana

or,

0=red
1=black

or, in the case we are discussing,

0=38kHz for 1.2mS
1=38kHz for 0.6mS
with 0.6mS of dead time in between.


I am yes, :confused:

I thought that a "1" was voltage high for 1.2ms, and a "0" was voltage high for 0.6ms followed by a delay(no voltage) of 0.6ms representing the "0", and all the other delays(no voltage)of 0.6ms in between the "1ns" were to supply a gap of no voltage so another "1" can follow?
 

Roff

Well-Known Member
shaneshane1 said:
I am yes, :confused:

I thought that a "1" was voltage high for 1.2ms, and a "0" was voltage high for 0.6ms followed by a delay(no voltage) of 0.6ms representing the "0", and all the other delays(no voltage)of 0.6ms in between the "1ns" were to supply a gap of no voltage so another "1" can follow?
I apologize. I got the times vs logic levels reversed. I will go back and edit my post. I think you have the idea. It should help you to realize that a logic 1 is not always a high voltage.
 

shaneshane1

New Member
Roff said:
I apologize. I got the times vs logic levels reversed. I will go back and edit my post. I think you have the idea. It should help you to realize that a logic 1 is not always a high voltage.

Thank you for your help Roff, i now understand that a "1" is not always a high voltage!!! :D

I've always wanted to know how this worked!

Thanks again for sticking through my noob questions.
 
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