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need help to build long range IR transmitter

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aruna1

Member
hey guys I'm trying to build a 38khz transmitter that works about 5m(at least) but its unsuccessful.currently I'm using this circuit. but it cant use more than 50cm. i have no idea how to increase rage.

8454-zkr9fs.jpg

equation is f=1/(0.8*R1*C1)
I have some NE555 and a 9V battery some transistors and couple of 0.1uf,0.01uf caps.can some one give me a circuit with higher range (at least 5m).
i know i have to give large current to IR led but i cant figure out a way to do that.

and i want some thing that will not eat 9v battery.
thanks
 

Mikebits

Well-Known Member
The value of R2 seems a bit large. I think your transistor is not turning on enough due to R2. Also R4 and d2 are just wasting current and are not needed.

I assume U1 is getting power as it is not shown.
 

Mikebits

Well-Known Member
R2 and D1 is for indication.
and can you suggest a value for R2?

You really don't need an indication, it is just bling. I have not looked at data sheet for your transistor but I would guess maybe a 1k or less resistor for R2.

You can experiment by dropping the value and see if range improves.
 

Mr RB

Well-Known Member
After fixing R2, reduce the duty cycle by putting a diode and resistor (in series) both in parallel with R1. That will give a shorter LED on cycle. I would try for an on duty of maybe 10%. Then after you tune the frequency back to the sweet spot you can increase LED on current by reducing R3.
 

aruna1

Member
You really don't need an indication, it is just bling. I have not looked at data sheet for your transistor but I would guess maybe a 1k or less resistor for R2.

You can experiment by dropping the value and see if range improves.
i'll chk,thanks
 

Nigel Goodwin

Super Moderator
Most Helpful Member
R3 is massively too big it wants to be at least only 10% of that, and preferably smaller - you really need 1A or so pulses through the IR LED.

You also don't want to feed it with continuous pulses, short bursts of pulses generated from a PIC are far better, and give a much longer range.

Check my IR PIC tutorial, it uses very few parts, and does 15m easily, as most IR remotes do.
 

aruna1

Member
Finally finished(i guess)

R3 is massively too big it wants to be at least only 10% of that, and preferably smaller - you really need 1A or so pulses through the IR LED.

You also don't want to feed it with continuous pulses, short bursts of pulses generated from a PIC are far better, and give a much longer range.

Check my IR PIC tutorial, it uses very few parts, and does 15m easily, as most IR remotes do.
well i was thinking using a pic for simple transmitter is a waste coz PICs are expensive here.:(
anyway i found a 555 circuit and it seems working (didn't had time to chk distance).
that means my project(remote fan controller) is finished.i used 12F675 in receiver and code is using 99% memory,so i had to remove few options).i probably i will be able to upload all details (description schematic source code etc, ) if i can finish documenting.(i guess there is a separate forum or something here to post projects:confused:)

thanks everyone for all of your help.:)
 

blueroomelectronics

Well-Known Member
You might be better off to use a regular TV remote control as the transmitter, they output data in pulse streams (your IR detector probably won't like continous IR)
 
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