Thanks but I didn't understood your second sentence:
You could replace it with one, but you would need to recalculate the series resistor, and output would be halved.
I thought that it is used to increase the coverage distance, isn't it?
Another thing, does each one send the same pluses at the same time , or the pulses is spreaded for the two of them?

when there is no signal, i know the input of the ir recevier is high so the BC549c will be on , the collector voltage will be low why? and how is that can anyone explain a littil bit..

 

If you remove one IR LED, the current trough the other one would be too high, so you need to increase R7 in order to limit current trough IR LED.

yes, with two led's you have more IR light hence more distance
yes, they send identical impulses if connected as presented in schematic

 

The IR Receiver is trigering RESET port of the oscillator via transistor. When the IR Receiver detect signal, it will release oscillator and oscillator will generate signal. when there is no signal, it will hold the oscilator. If that is not clear, check out the data sheet of ne555

 

They are in series, so both obviously transmit the same thing at the same time - it's common practice in remote controls to use two LED's.

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i need to know what is the purpose of the 10 kohm resistor at the input stage, thanks.

http://english.cxem.net/infrared/ir7.php

 

Its the collector load resistor for Q1 transistor.

When Q1 base receives a postive signal it conducts and pulls the RESET line low, which RESET's the 555.

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Eric
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what is the purpose of 47 micro capacitor on the 555 timer,
and why the DIS pin not connected to anything, and why they used one resistor with the 555 instead of 2 as in astable mode.

 

The 47uF is decoupling the 12V

The DIS pin is not connected as the 555 is not being used as a conventional astable

Its not an conventional astable.


EDIT: the text with the circuit diagram explains the function of the 555

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Eric
"Good enough is Perfect"

PIC tutorials:
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Bill's: www.blueroomelectronics.com/

 

what is decoupling cap? what does it do?
and what do you mean by conventional astable? and if i want to explain about why in this circuit I didn't use the equations that establish the values of the resistors and capacitors , what must I say ?

 

hi Abeer_engjbr,
May I ask what subject you are studying and the year you are in.?

I would like to help, but if you dont know the basics its going to be difficult..

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I am a senior , but i used this circuit in my project and I need to know evrdetail about it, to be able to answer any question.
If you may answer on my last reply please am such in a hurry and am running out of time.
Thanks.

 

hi,
The attached jpg shows the formula for the timing also it explains that the 555 is connected as an oscillator with an equal marl/space ratio [On/Off]

The 47uF is on the circuit in order to hold the +12V line at a 'constant' voltage as each part of the circuit draws current from the +12V, especially the IR LED drivers.
Without the 47uF, every time the IR pulsed the +12V would drop slightly in voltage, this could affect the 555 timing..OK

Attached Images

screenhunter.jpg (40.7 KB, 3 views)

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hi everybody,

I need to know how does an IR reciever do demodulation? what is the process of the demodulation?

The datasheet for it is attached and it is used in following circuit:
IR Remote Control Extender Circuit (Mark 4)

Thanks

Attached Files

datasheet.pdf (204.7 KB, 2 views)

 

Yes, it removes the 38kHz carrier. It is also active low out and has a built in pullup. I use them in my Junebug & Firefly kits. You also need the 100ohm & 4.7uF cap on its power pin if you're powering it from 5V.

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Hi,
I know that it removes the 38 kHz , but how that is my question.