4 X 3V Leds In Series - Do I Need A Resistor?

[agent_zed]

Hi,

been reading about leds and not sure if i understand correctly. They seem to suggest you need a resistor. If you buy a 12v LED and run it off 12V it seems to suggest you still need a resistor ( a largish one at that). It seems to suggest you are better wiring 3 x 3v (i don't know why not 4) leds in series with smaller resistors for each as that has less loss than one big resistor.

 

I don't know why i can't either use a 12v LED straight off 12V supply or 4 x 3v LEDS run in series without resistors.

 

anybody shed any light on this?

 

thanks

[philshelton]

With engine running you may be feeding up to 14.8 volts through,

[agent_zed]

ah won't be engine. Sadly it's not for the car. It will be a 240v to 12vdc converter output. So i guess it relatively stable..

 

So would i be correct in thinking it would be less important having resistors on a regulated 12vdc supply? or is it just best to put them in?

 

Although as a side note i was thinking of getting some more of the 12v leds strips for use under the dash as they are pretty good so i guess i would need a big resistor for that as it comes as a stick on strip (although they might have a resistor built in i'll have to check).

[Guest 2b cruising]

The only place I have needed any type of resistor is for the indicators for the flash rate.

Nearly finished mine to the supplied instructions and all direst off 12v.

Indicators still 12v but through a suitable relay. £11.00. Three Britism made, three year warranty.

[fry61]

Leds are best in parallel (with series resistors ) if one fails 3 will remain on -- in series 1 fails all stop or all fubared if dead short on one due to over-voltage.

[agent_zed]

Thanks guys. Maybe ill have a play and see what happens. They aren't expensive so if I fry a few its not a huge problem.