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RollingEEE
Joined: 25 Mar 2006
Posts: 208
Helped: 4
Location: Bangladesh
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 05 Apr 2008 14:56 generator 38khz to microcontroller |
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I am working on a project to transmit data from PC to a microcontroller. I wrote my own protocol for transmission (A variation of PWM) But I can't get the IR receiver work. I have a 3 pin receiver. It is written on it 6038. It seems that it means the Receiver will work with 38 kHz carrier signal. I used a nice function generator on our lab to transmit 38kHz infrared. I connected a LED with 10k resistor to the output pin to see the output. When the freq varying knob is rotated past 38kHz, the LED lights up for, say 0.5 sec and then it goes down. If I send a very low freq square wave, say 300 Hz, the LED lights up dimly. Later I found out when any change of the IR is done (like putting your hand infront of the receiver), a pulse train is created that lasts about 0.5 sec, has 10% duty cycle. Is it a malfunction of the device, or am I doing it wrong?
My IR receiver is black, has a half sphere in front of it, and no metal casing. I connected a 100R resistor and 4.7uF capacitor to form a low pass filter to block the noise of the microcontroller too.
Please help me out.
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penoy_balut
Joined: 08 Sep 2007
Posts: 149
Helped: 16
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05 Apr 2008 15:16 ir with a microcontroller |
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| you need to data modulate the 38khz carrier frequency for your IR to work, another requirement also is DC balanced transmission, search about RC5 protocol it is easy to learn
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RollingEEE
Joined: 25 Mar 2006
Posts: 208
Helped: 4
Location: Bangladesh
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05 Apr 2008 15:22 ir receiver times out |
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| That means the receiver will block out the 38kHz continuous wave? RC5 uses bi phase manchester, that is too complecated. I wanted to use PWM. 2ms pulse = transmission start, 1ms pulse = 1, 0.5ms pulse = 0. Can I do that?
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penoy_balut
Joined: 08 Sep 2007
Posts: 149
Helped: 16
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05 Apr 2008 15:59 ir pulse receiver |
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| data modulation of the 38 khz carrier frequency is similar to that of OOK (on off keying) but need to be dc balanced, about pwm check your IR receiver datasheet, there's a requirement for maximum pulse width, the one i used has a maximum of 600us pulse width which means a 1ms pulse will not work
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05 Apr 2008 15:59 Ads |
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RollingEEE
Joined: 25 Mar 2006
Posts: 208
Helped: 4
Location: Bangladesh
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05 Apr 2008 17:52 Re: IR Receiver with microcontroller |
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ok, i'll try OOK. Now tell me, why a suddent interrupt in the 38kHz wave causes a spike train for 0.5sec? And also, why a 300Hz wave causes a continuous pulse train
Added after 5 minutes:
what is digital balancing?
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sajal1975
Joined: 25 Mar 2005
Posts: 150
Helped: 3
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05 Apr 2008 18:03 Re: IR Receiver with microcontroller |
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| i want a circuit for ir receiver with transmitter on 89c51.
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RollingEEE
Joined: 25 Mar 2006
Posts: 208
Helped: 4
Location: Bangladesh
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05 Apr 2008 18:06 Re: IR Receiver with microcontroller |
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| bro, thats what i am trying to make. but with avr
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padmanabhamh
Joined: 08 Mar 2006
Posts: 7
Helped: 1
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05 Apr 2008 18:32 Re: IR Receiver with microcontroller |
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| hmm, there is time out for your receiver module, it wont give continues low if continues 38khz modulated IR light is there. check datasheet of part which you are using or TSOP1738 etc.
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