LED Spots - One brighter than the other

[cafemaestro]

Have just fitted a pair of LED spots as shown on this thread http://www.ukgser.com/forums/showthread.php?t=233268&highlight=auxilliary Unfortunately one is much brighter than the other.

I have joined the wires for the spots together and then wired in an autoswitch via a relay that is powered off the auxiliary socket as per autoswitch wiring diagram. All works fine but the spot furthest away from the relay is approx half as bright as the other one.

Any one got any clues?

My only guess is that the one closest to the relay steals all the juice from t'other. If so, what can I do?

Would appreciate the collective wisdom

 

[stolzy]

These lights exist in two types. The multi-mode versions have various flashing modes and three levels of intensity. You switch between them by flicking them on and off. These are amusing, but entirely useless on a bike.

The single mode ones just stay on full intensity permanently.

You may have the multi-mode ones. You can check this by flicking them off and then on again - they should start flashing. If this is the case you'll probably want to send them back for an exchange.

If they are single-mode lights maybe one of the thres LEDS has gone - put some very dark sunglasses on and have a look

 

[hops]

check

the earth wire has a good clean connection.

 

[STUBBS]

try swapping the lights around to see if its the lights or the wiring

 

[mr badger]

Check wiring to see if they're wired in series or parallel. Easily done (DAMHIK).

If in series, the voltage drop across the first will affect the second.

 

[cafemaestro]

Still squinting

Many thanks for the suggestions.

I have since:

a) checked the earthing - all ok
b) rewired the lights to ensure that wires etc are equal to each lamp
c) checked that I have the non-flashy type of light
d) checked all the LED bulbs are working,

put it all back together again and -

Same problem! I can only think that I have one dodgy lamp....

unless anyone else has any ideas.....?

 

[stolzy]

Many thanks for the suggestions.

I have since:

a) checked the earthing - all ok
b) rewired the lights to ensure that wires etc are equal to each lamp
c) checked that I have the non-flashy type of light
d) checked all the LED bulbs are working,

put it all back together again and -

Same problem! I can only think that I have one dodgy lamp....

unless anyone else has any ideas.....?

Are they the type with three LEDs? if so, can you see all three are lit?

You'll probably need a couple of pairs of sunglasses

 

[GSwadd]

Could be dodgy. Most high power LED's have circuitry attached to reduce power if/when they get hot. This equates to reduced light output and, therefore, heat.

 

[cafemaestro]

Could be dodgy. Most high power LED's have circuitry attached to reduce power if/when they get hot. This equates to reduced light output and, therefore, heat.

Strange you should say that - the brighter lamp is running much hotter - I am reluctant to run it for long because of the heat.

Stolzy - I've checked the lamps - they are the 3 LED types and all 3 are lit.

I have also disconnected both lamps and then reconnected them one at a time - same result - one is brighter that t'other - ergo I reckon a duff lamp.

 

[Womble]

Have you swapped the lights around?

Does the problem move with the light, or does it stay with the wiring?

 

[cafemaestro]

I haven't swapped the lights, just connected them individually one at a time. One lamp is definitely brighter and hotter than t'other - about twice as bright. I doubt it is a wiring issue as the only thing I changed was the lamp and its 6" of cable.

Arse

 

[Sempione]

I'd have a word with the manufacturer.
My guess is that you have two lights with LEDs from different reels (different forward voltages) run directly off the DC supply. See below for a bit more detailed explanation.

A variation is normal up to some degree. There is a sort of LED lottery and a good reason why high quality LED lights can be a bit pricey.
All major high power LEDs (Luxeon, Cree, Seoul Semi Conductor) products are sorted and "binned" to give some degree of control for the variation of performance.
The sorting criteria are usually luminous flux (brightness), color tint and forward voltage.
It could be that the manufacturer did not have full control over the LEDs supplied and the LEDs for one of the lights just came off a reel with different specs.

Since the light is running a lot hotter and brighter it sounds like a current regulating driver between the DC supply and LED is either completely absent or faulty.
LEDs are current driven and not voltage driven like incandescent bulbs.
I've driven LEDs directly from DC for better performance but this requires a very careful selection of forward voltage to get close to but not exceed the maximum current rating of the LED. It also requires a relatively large heatsink even for small LEDs to ensure a long enough lifetime for the LED.

 

[Sempione]

Want to make my guess a bit more specific.

Three LEDs run in series without current regulating driver and LEDs with different forward voltages in the two lights.

 

[cafemaestro]

Want to make my guess a bit more specific.

Three LEDs run in series without current regulating driver and LEDs with different forward voltages in the two lights.

Okay........(I think) so is there anything you can do to fix it or is it a new lamp?

 

[Sempione]

I'd try and measure the current draw for both lamps.

I can only guess what the problem is. Maybe I'm not doing the manufacturer justice. It could easily be a constant current regulator set at the wrong current limit.

Contact the seller/manufacturer and let them try to sort it out for you.

Modding lights/torches can be a bit addictive and a money pit. In some cases I ended up gutting the lights completely and using only the housing (after machining and hard anodising ).
If you decide to go that way I can recommend LED drivers from www.taskled.com.