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attabros
Joined: 28 Jul 2008
Posts: 35
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| Infrared data transfer |
 Posted: Fri Oct 24, 2008 8:06 am |
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Hi all,
I want to transfer a continous data through IR. What frequency
should I select to transfer the data ? Should I use the same as in
remote control applications which is 38KHz or some other frequency ? |
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Ttelmah
Guest
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| Posted: Fri Oct 24, 2008 8:56 am |
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Depends totally on what you want to do.
Basically, the faster you work, the more complex the drive circuitry needs to be for a given range. At low speeds you have increased risk of picking up other sources. 38K, was fast enough to make it unlikely to pick up flicker from the TV itself (when this was first used, under 20K), or other 'household' sources, and gave a fast enough data rate for the simple commands needed. It is also slow enough to be directly decoded and generated by a fairly simple microprocessor, without involving external complex hardware.
However if you need higher tansmission speeds, then consider IRDA, or going completely 'DIY', for really fast links. Depending on the reliability needed, and the enviroment involved (can you 'aim' the receiver/transmitter - rain or fog, likely objects to break the link, etc. etc.), you will need to consider methods of error correction or recovery.
Depending on the range, and likely power needed, you then may run into 'regulatory' requirements.
For higher data rates, you would probably want to consider a link that doesn't use a 'carrier' as such, but instead codes the data so that the the transmission frequency can be recovered using a PLL from the data stream itself.
IR, covers a whole 'suite' of technologies, giving link rates from a few Hz, to hundreds of MHz.
Best Wishes |
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Rohit de Sa
Joined: 09 Nov 2007
Posts: 282
Location: India
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attabros
Joined: 28 Jul 2008
Posts: 35
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| Posted: Fri Oct 31, 2008 6:31 am |
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The IR receiver range is more than 10 metre which is enough for
my requirement i have checked it with test circuit now i m going to test it
sending PIC 16F877A can any one provide me simple program for both IR transmitter & receiver side if i just send a data to blink an LED on the receiver side so that i can understand how the IR devices configured with
PIC controller. How to use PWM why we use it what is the purpose of PINS CCP1 & CCP2.
Kindly help me out.
Thanks |
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Rohit de Sa
Joined: 09 Nov 2007
Posts: 282
Location: India
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| Posted: Fri Oct 31, 2008 7:18 am |
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| Quote: | | The IR receiver range is more than 10 metre |
Usually, the 'range' of the complete system is specified; not just of the receiver. The range depends on both the receiver and the output power of the IRLED. If you only want to talk about the receiver you would talk about its 'sensitivity'.
| Quote: | | i have checked it with test circuit now i m going to test it |
Since you've already checked it, I'm sure you understand something about it. Please write a few lines of code yourself first. We will certainly help you out if the code is wrong. See, its your project, and a little effort on your part is expected.
You haven't mentioned the IR sensor that you are using, but if it's the TSOP series, remember that the sensor will only respond to data modulated at a particular frequency. For the TSOP1738 this frequency is 38kHz. The TSOP output pulls low when 38kHz IR light hits it. If you simply want to turn an LED on and off use a PIC to output a 38kHz square wave (this can also be done with a 555 timer) to an IRLED. Connect an indicator LED to the TSOP output. Beaming IR light at the TSOP will cause its output to swing low. You will need to connect the LED appropriately to see an active low or active high output.
Rohit |
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attabros
Joined: 28 Jul 2008
Posts: 35
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| Posted: Sat Nov 08, 2008 9:14 am |
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Hi
I have built an IR transmitter on vero board & configure the PWM mode at 38KHZ & 50% duty cycle but slightly confused how I will send data
on the CCP pin which is C2. Lets suppose I send two bits 1 & then 0
with delay. How it will be possible ?
Thanks |
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