Some of the new high-bright LEDs needs a slightly higher voltage than the traditional LEDs.
Using a small-signal transistor as a sort of relay, it is very simple and easy to use the old LED signal to turn the new bright LEDs On/Off.
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This is a diagram of such an electronic
switch. It should cost you no more than US$1-2 for all the parts.
The trim pot. can be 470 ohm. The 10K ohm resistor is to protect the transistor.
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Regular LEDs use 2.2 to 2.4 volt, where as some of the brighter LEDs needs 2.6 to 3.2 Volt to work. (See tables below)
With the use of a transistor and two resistors, one can make a low power switch that is controlled by the power from the old green LED, and it will supply enough voltage to make the new flashier LED work.
The transistor can basically be any small-signal NPN transistor, capable of running minimum 25mA
For odds and ends I use these two kinds; the BC547 runs a max of 100mA, the BC639 runs a max of 500mA.
Unless specifically noted otherwise, LEDs should not be run higher than 20mA
