need help to build long range IR transmitter

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.



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).

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

You might try these. Both are basically the same, just minor modifcations. Works at 38KHz and gives a maximum range of 10mtrs.

If you need to go lower, get a savaged TV remote, take its chip and make a tiny remote with it. Will need only 3v, also gives 10mtrs range and you can have as many buttons as you need. Overall size would be small too..

thank you.

If this is related to your other thread on IR detection and you are using the TSOP1738 (or any similar packaged detector), your short range may be related to the fact that you are not modulating the 38KHz IR-carrier appropriately for the detector. That was mentioned here: http://forum.allaboutcircuits.com/showpost.php?p=158949&postcount=12

Dual 555's or a 556 will do that fine.

John

jj_alukkas said:

You might try these. Both are basically the same, just minor modifcations. Works at 38KHz and gives a maximum range of 10mtrs.

Click to expand...

i tried 1st circuit with slghtly different values.and i also add a current limiting resistor of 15ohm in series with LEDs.but it seems its too small.i have to increase it i guess.here is the schematic

hey jj_alukkas,

Can u also post a compatible receiver for your transmitter ?

Cheers

aruna1 said:

i tried 1st circuit with slghtly different values.and i also add a current limiting resistor of 15ohm in series with LEDs.but it seems its too small.i have to increase it i guess.here is the schematic

Click to expand...

Your BC547 is upside down. Its emitter should be connected to 0V and its collector should be connected to the LEDs. Look at its datasheet: its max allowed collector current is only 100mA so a more powerful transistor should be used.

Look at the datasheet for the 9V battery. It cannot supply enough current so a supply bypass capacitor should be added.

The 555 must have a short duty cycle so the IR LEDs do not burn out and so the battery does not die so quickly.

Look at your other thread and look at the datasheet for the TSOP IR receiver IC. It needs the 38kHz pulses to be in bursts for its gain to remain high. Then you need a second 555 to turn the 38kHz oscillator on and off.

what do you mean long range?5 meters or 5 miles.
dmsmith.