Led cabin light diy problem

[Ardenfour]

I recently bought some led lamps on eBay, and have tried to modify my cabin lights from festoon bulbs to the new leds. The cabin lights are Hella brand and switch on and off by turning the clear diffuser. There are two on positions and I wired it so as to give a bright and dim on functions. I added a resistor to create the dim function. And a diode in the bright position to drop the voltage as with a charger connected the light was too bright and the leds ran quite hot.
So now the bright and dim intensities are spot on, but the problem is in the bright position the lamp begins to pulse after about 10secs. I have wired two lights and both behave in this way. Any ideas how to cure this? Both are fine in the dim position.

 

[nigelmercier]

Flickering LEDs are a sure sign that the current is too high.

 

[rogerthebodger]

I have some of those LED and they run on 9 volts not 12 v so you need a resistor to get the correct voltage even in the bright.

William_H has done some work with these and posted a while ago and the correct setup.

I would also ensure the back of the LED is incontact with the metal backplate as a better heatsink.

 

[yotter]

Why not try Adrian at Boatlamps.

http://www.boatlamps.co.uk/index.html

Give him a phone, he knows is stuff.

Best regards
Angus

 

[VicS]

Why not try Adrian at Boatlamps.

http://www.boatlamps.co.uk/index.html

Give him a phone, he knows is stuff.

Best regards
Angus

l
And will be able to supply suitable LED based festoon bulbs l

 

[Jamesuk]

I have some of those LED and they run on 9 volts not 12 v so you need a resistor to get the correct voltage even in the bright.

William_H has done some work with these and posted a while ago and the correct setup.

I would also ensure the back of the LED is incontact with the metal backplate as a better heatsink.

or a transformer. We had to drop 24 volts to 9 volts for the LED night lights at shoe level

 

[dilly]

I bought 42mm long LED festoon bulbs in a pack of 2 delivered for £3 in total per pack from eBay

 

[William_H]

I bought 42mm long LED festoon bulbs in a pack of 2 delivered for £3 in total per pack from eBay

No need to buy more LED. Those you have are probably rated at 5 or 10 watts. I suggest you check the actual current drain on high. I am a bit confused but some of these COB (chip on board) LED don't seem to have a current limiting resistor internally so need current control external. A resistor in series on high brightness around 4.7 ohm would be a good start and I think will stop the flickering which as said probably relates to LED too hot. good luck olewill

 

[Ardenfour]

Many thanks for the advice. I got some 5w 4.7 and 10 ohm resistors today, will try them and see.

 

[Tammany]

Heat?? Powerful led and not much in the way of a heatsink. Maybe getting too hot and led stressing out.

 

[salar]

Are they interfering with your VHF as well? In my experience messing with non-marine LED lights causes other problems not just the lighting.

 

[William_H]

Current control for LEDs comes in 2 forms. The simple crude resistive or linear regulator type can not cause interferencee as there is no rapid switching involved. It is however inefficient compared to...
Switch mode regulation uses rapid switching off and on to limit average current, So very little heat loss from power wastage.
But this rapid switching can be a source of interference if not effectively controlled by bypass capacitors metal boxes and series inductors. The above referred to LED current control by resistor does mean a variation in light with battery voltage but can not cause interference. olewill