cortay
Something must be wrong, this is not correct?

First go to http://www.dannyg.com/examples/res2/resistor.htm look at your resistor and plug in the colour bands, check you are using the resistor you think your using. Then I need the following info:

For calculating :-
   Power Source Volatge:
   Visay IR-led Model:

For Interest :-
   Power source size (N, AAA, etc):
   Power source type (Alkaline, NiCd, Nimh, etc):
   Power source brand:
   Rigging Wiring (hot glue, solder, mechanical, hand held):
   Wire Diameter:
   Resistor size using (ohms):

Benpaddlejones

Cortay
You should be using a 1/8w 1.5ohm resistor (Brown/Green/Gold/Gold).

If you are using the wrong resistor I suggest you use the correct one, as it will prolong the life of your IR-Led. You also may want to check the quality of your battery. Cheap batteries whilst saying 1.5v often are around 1.3v and have very quick drain rate. In this case a resistor is not needed.

Simply:
1. Make sure you have the correct resistor
2. If you are using a quality full powered battery, then yes use a resistor
3. If you plan to use low quality battery then no a resistor is not needed

Benpaddlejones

i dont think resisitor is required since the max forward current is 1.6v. it should be able to take it without any resistor