Led Question

[BD13UK]

Is there a problem with different voltages etc with Led's or can any type be used for pedal's.
Thank's

[Mike Burgundy]

different LEDs will need different resistors to get the right brightness/prevent burning them up, but that's about it.

[gez]

Is there a problem with different voltages etc with Led's or can any type be used for pedal's.
Thank's

Look through your suppliers catalogue and you'll see (hopefully) that forward voltage (Vf) figures are given.  This tells you the forward voltage drop needed across the LED for current to flow.  Subtract the figure from your supply voltage and the remainder is the voltage that appears across your current limiting resistor.  This helps you to calculate values for this resistor.

If the Vf was 2V and the supply 9V, you'd have 7V across the resistor.  If you wanted 2mA through the LED you'd need 7/.002 ohms of resistance (nearest value 3k6).

You'll see that many LEDs have pretty similar Vf figures.  How much current is needed to produce a reasonable amount of light will vary, but figures should be quoted for this too, which will give you an idea of how efficient the LED is.