Every LED must be protected against unrestricted DC voltage - they must have a resistor to limit current or they will blow!
The short lead on an LED is the ground connection.
A very good tutorial on driving LEDs is Don Klipstein's LEDs 101. His article clearly explains how to drive LEDs and determine resistor values.
The only exception is when low voltage, high internal resistance small clock batteries are used. That is why you see in some novelty items a couple of batteries and no resistor.
But don't push the limit. Always use a resistor! The super brights ordered for this receiver are expensive LEDs and money is easily thrown out the window when a resistor is not used.
The above circuit can be used to test all the LEDs received with the kit.
If you don't get light from an LED, use the diode tester in a VOM/DVM and see if it shows a forward voltage drop reading. If it does, then the LED you are testing is probably an IRED, which do not emit visible light.
The IREDs with the kit have a dark smoked lens, which easily sets them apart from the visible ones. However, ones ordered from BG Micro, or other places, may have a clear lens.
Be careful! It is very easy to put the clip leads of a power supply on the leads of an LED without thinking of using a resistor. I have a boxful of blown LEDs to prove the point!
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