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Help with 38khz long range IR emitter circuit

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indika perera

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hello...anyone can give me a 38khz long range IR emitter circuit that have used a some kind of similar chip that are using on TV remote controllers..i have seen many circuit on web that are using Ne555 or Ne556 chip..BUT Ne555 is not enough in this case..i just only need 38khz beam so no need of programmable...or more switches..
BUT don't say "why don't you use old TV remote control for this instance?' Because i need small assemble rather than TV remote....and other thing is most TV remotes have fix chips that can not remove..as well as i haven't good knowledge on electronic too...
 
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Hi,

How long range? How far?
555 will do it with an added driver transistor.
 
I would expect a 555 to be adequate for 10m range. It can source/sink 200mA. What is the current rating of the IR LED you are proposing to use?
 
Hi again,

I was going to suggest multiple IR LEDs for long range but yeah it depends on the range needed.
 
hi!..most of the time i heard that 555(i have tried with 555 lot but it does not reach at least 1m-i used high gain IR led too) is said to be enough for (say..) up to 10m for IR emitter circuit ..but nobody talk about beyond that.so i have never found a proper circuit on such case..apart my TV remote control..I do not know what the reason is? i think that remote control IC chips are not available or most of the time people move for other option such as laser beam.. If somebody can give me a such modulated IR emitter circuit with only one switch....i would be big help for me....thank you..all..
 
i have tried with 555 lot but it does not reach at least 1m-i used high gain IR led too.
Are you saying you can only get 1mA drive from the 555, or 1 metre range? Either way, I find that surprising if the 555 output is being used correctly. Can you post the circuit you tried and which didn't do what you want?
 
Ah, but that circuit can only provide about 20mA maximum through the LEDs. You need a much higher peak LED current. The LED is pulsed at 38kHz so it is the peak pulse current rating, and average peak current rating, which are of interest. You haven't replied to my earlier post asking for the current rating of the LED you used. Are you using the Vishay 1738 (as shown)?
 
actually..i'm not expert in electronics...mate..thx for helping..i have not used vishay1738..but similar available one that response to 38khz..also i used several IR leds...and old remote control IR LED too...
 
From my use of this style of circuit is they work very well, BUT......... if the frequency is not correct for 38 to 40khz then the distance will be greatly reduced.

I think the problem is not the circuit design but more to your ability to be able to set the correct frequency of the circuit.

If you dont have a frequency meter than it becomes hard to tune the circuit.
You could try to place the receiver about 2 meters away then with the ir leds facing the receiver adjust the frequency till the receiver works, then move the receiver 1-2 meters further away and fine tune it again, and so on till you get the distance required, it is how i done it many years ago before i had a frequency meter.

Another circuit would be have a look at the 08m picaxe as it supports IR, but is really an over kill for such a simple project.

The commercial IR alarm beams only go to 10 meters on average so i think that is the limit of the IR range, and the 2 large 10m IR alarm sensors i have are about 500mm long and 100mm wide, with some rather clever focus adjustment systems, so i doubt if you will acheive the results you want by just pointing the led in the direction of the sensor and expect it to work over the distance.

Pete.
 
did you know any cheep and available micro chip that can used to build single channel IR remote that gives 38khz..with high current gain..? i got a one but 8 channel..but i don't know whether it is possible to get that micro chip in my country... this is the one....**broken link removed**
 
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From my use of this style of circuit is they work very well, BUT......... if the frequency is not correct for 38 to 40khz then the distance will be greatly reduced.

I think the problem is not the circuit design but more to your ability to be able to set the correct frequency of the circuit.

If you dont have a frequency meter than it becomes hard to tune the circuit.
You could try to place the receiver about 2 meters away then with the ir leds facing the receiver adjust the frequency till the receiver works, then move the receiver 1-2 meters further away and fine tune it again, and so on till you get the distance required, it is how i done it many years ago before i had a frequency meter.

Another circuit would be have a look at the 08m picaxe as it supports IR, but is really an over kill for such a simple project.

The commercial IR alarm beams only go to 10 meters on average so i think that is the limit of the IR range, and the 2 large 10m IR alarm sensors i have are about 500mm long and 100mm wide, with some rather clever focus adjustment systems, so i doubt if you will acheive the results you want by just pointing the led in the direction of the sensor and expect it to work over the distance.

Pete.


Thx..buddy...really...helpful
 
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Ah, but that circuit can only provide about 20mA maximum through the LEDs. You need a much higher peak LED current. The LED is pulsed at 38kHz so it is the peak pulse current rating, and average peak current rating, which are of interest. You haven't replied to my earlier post asking for the current rating of the LED you used. Are you using the Vishay 1738 (as shown)?
Thx..buddy..for your thoughts...
 
The circuit posted here with two IR LEDs has only 42mA in the LEDs and the circuit posted with one IR LED has only 16mA.
But TV remotes blast a current of 1A in their IR LEDs. The current is 24 times to 63 times higher.

Read the datasheet of the TSOP1738. It is an IR receiver IC that has automatic gain control that reduces the gain (which reduces the range) when continuous 38kHz IR pulses are received because it is designed to ignor 38kHz IR pulses from a compact fluorescent light bulb but have full gain for a range of 10m when the 38kHz pulses are received in bursts that are described in the datasheet. You need a second oscillator to modulate the 38kHz oscillator in bursts.
 
The circuit posted here with two IR LEDs has only 42mA in the LEDs and the circuit posted with one IR LED has only 16mA.
But TV remotes blast a current of 1A in their IR LEDs. The current is 24 times to 63 times higher.

Read the datasheet of the TSOP1738. It is an IR receiver IC that has automatic gain control that reduces the gain (which reduces the range) when continuous 38kHz IR pulses are received because it is designed to ignor 38kHz IR pulses from a compact fluorescent light bulb but have full gain for a range of 10m when the 38kHz pulses are received in bursts that are described in the datasheet. You need a second oscillator to modulate the 38kHz oscillator in bursts.

Oh...that might be the case...that's way...that receiver circuit response to Tv remote....but not to my one....i have not used TSOP1738 but that one too have continuous pulse ignoring....i think i can use ne556...for both first and second oscillating... Is n't it?
 
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