Board logo

LED Rain light wiring
FFTS - 21/12/09 at 11:15 PM

I have a pair of 50 x LED rain lights and want to wire them as high level brake lights. Can they just be wired in parallel to the main brake lights or do they need anything in between being LED's?

Chippy - 22/12/09 at 12:02 AM

If they already have resistors built in then you can just wire them in. Or they may be 12v LED's, hard to say without seeing them. Thats not much help is it, Cheers Ray

Edit to add: Yes please, would like some help with my, ermmm, kit.

[Edited on 22-12-09 by Chippy]

welderman - 22/12/09 at 08:01 AM

lol.

Edit to add: Yes please, would like some help with my, ermmm, kit.


sucksqueezebangblow - 22/12/09 at 10:47 AM

quote:
Originally posted by FFTS
I have a pair of 50 x LED rain lights and want to wire them as high level brake lights. Can they just be wired in parallel to the main brake lights or do they need anything in between being LED's?


No need for ballast resistors as they are not indicators (indicators need them to stop the standard flasher unit flashing too fast under light load). Just wire them straight in in parallell to the brake lights.

02GF74 - 22/12/09 at 12:14 PM

I'm with Chipy on this one since Ihave no idea how they are wired up.

if they as just LEDs, then you are better off wiring about 8 in series with a drop resistor for use on 12 V - wil reduce current and cost in resistors.

sucksqueezebangblow - 22/12/09 at 12:34 PM

quote:
Originally posted by 02GF74
I'm with Chipy on this one since Ihave no idea how they are wired up.

if they as just LEDs, then you are better off wiring about 8 in series with a drop resistor for use on 12 V - wil reduce current and cost in resistors.


Sorry mate, I disagree. If they are 12 volt LED rain lights they have their own resistors built in (check the destructions to be sure) and will draw very little current. They should be wired in parallel.

Of course if you were making up your own rain lights from discrete LEDs then you would have to calculate the appropriate drop resistance to add to run them at the correct voltage.

Just for clarity, ballast resistors are different from drop (pull-up or pull-down) resistors. Ballast resistors are designed to be placed in parallel to INCREASE the current draw of LED indicators so that flasher relays that were designed for incandecent bulbs have enough current drawn through them to make them flash at the correct intervals. Without the ballast resistors they will flash too fast. Ballast resistors are a wasteful solution, a better solution is an electronic flasher relay designed for LED indicators.

iank - 22/12/09 at 12:39 PM

The LED rainlights are designed to be wired up direct to 12V - they should just have 2 wires 12v and earth/ground/0v. Don't wire them backwards or they will probably be destroyed.

Note maplins sell something that looks identical for 1/4 the price of ones with an FIA sticker
http://www.merlinmotorsport.co.uk/p1454/HIGH-VISIBILITY-RAIN-LIGHT-FIA/MSA-APPROVED/product_info.html

http://www.maplin.co.uk/Module.aspx?ModuleNo=12696

sucksqueezebangblow - 22/12/09 at 12:47 PM

quote:
Originally posted by iank
The LED rainlights are designed to be wired up direct to 12V - they should just have 2 wires 12v and earth/ground/0v. Don't wire them backwards or they will probably be destroyed.

Note maplins sell something that looks identical for 1/4 the price of ones with an FIA sticker
http://www.merlinmotorsport.co.uk/p1454/HIGH-VISIBILITY-RAIN-LIGHT-FIA/MSA-APPROVED/product_info.html

http://www.maplin.co.uk/Module.aspx?ModuleNo=12696


The Maplin one needs a 10 Ohm resistor to drop the voltage to 9.6V

iank - 22/12/09 at 03:39 PM

quote:
Originally posted by sucksqueezebangblow
quote:
Originally posted by iank
The LED rainlights are designed to be wired up direct to 12V - they should just have 2 wires 12v and earth/ground/0v. Don't wire them backwards or they will probably be destroyed.

Note maplins sell something that looks identical for 1/4 the price of ones with an FIA sticker
http://www.merlinmotorsport.co.uk/p1454/HIGH-VISIBILITY-RAIN-LIGHT-FIA/MSA-APPROVED/product_info.html

http://www.maplin.co.uk/Module.aspx?ModuleNo=12696


The Maplin one needs a 10 Ohm resistor to drop the voltage to 9.6V


If you look at the datasheet Vmax is 12.5V. I suspect they are identical units.
The 12.5V max will come from worst case temperature/constant running/long lifetime (for the big displays they are designed for). I'd be happy running them off a car battery for short durations (brake light) and when it's low temperature (in the rain) without a resistor.

nz_climber - 22/12/09 at 10:06 PM

I would run with a resister if Vmax is 12.5V.. Remember with a car running and alternator charging you are likely to see 13.5v-15v... Depending on Alternator.

[Edited on 22/12/09 by nz_climber]

FFTS - 22/12/09 at 11:33 PM

Stuck one across the battery terminals today and no problem... VERY bright

iank - 23/12/09 at 12:21 AM

quote:
Originally posted by nz_climber
I would run with a resister if Vmax is 12.5V.. Remember with a car running and alternator charging you are likely to see 13.5v-15v... Depending on Alternator.

[Edited on 22/12/09 by nz_climber]


As I indicated, my point is Vmax is specified conservatively based on being lit permanently in worst case conditions (either -40 or 70 degrees C) and having to last years on a big sign where their customers won't be impressed at having to have them replaced weekly.

Over-volting LED's tends to shorten their life while burning brighter. Being used as a rain light/high level brake light, at even 14.8volts, will still have them lasting years as they aren't on for huge amounts of time (either a few seconds now for, say, 5mins per day total or for 30mins 4 times a season).

I'm betting the units with the FIA/MSA stickers are exactly the same units as the clusters being sold by Maplin (both 52mm, 50 LED's) and won't have extra resistors added.