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Discussion Starter #1 (Edited)
There has been much discussion here - This is a fresh thread with some updated diagrams, and some condensed information from other threads.
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WHY you might want to consider using a regulator:

LEDs are a diode. A diode allows electricity in one direction only, and is effectively a direct connection, a dead short (other than the minuscule drop across the diode itself.) Small diodes can only carry a small amount of current before they will pop like a fuse.

All LED fittings that are designed to operate at a given voltage (whether that is 5v or 12v or 24v or even 240v) are therefore fitted with an in-line resistor that will limit the current passing through the diode when it is operating at that specified voltage, so that the current is limited to the 'safe' figure for that diode.

The issue is that a resistor is a fixed component. If the operating voltage is higher than it was specified for, then more current will pass - there's no way round that.

The risk then, is all down to the original designer, who has to strike a balance between allowing a little leeway for a safety margin, and also wanting as much current to pass through as possible as this directly determines how 'bright' the fitting will be. Therefore, most fittings designed for 12v are running as close as they dare to the 'safe' current limits for the diodes being used.

So - running an LED fitting designed for 12v at a higher voltage, let's say 13.8v - well thats a 15% higher figure than they were designed for, therefore 15% more current will be passing. Your van will typically have 13.8 - 14.4v floating around both while driving or while charging the van or leisure batteries.

SOME fittings will cope with that just fine. Some will simply have a shorter lifespan, some will be ok til there's a spike and then blow. Some people have no issue at all, and others have experienced multiple LED fittings fail.

A built-in resistor will NOT protect it from a spike, at all - thats not what its designed to do.

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A regulator does a different job. It provides a constant voltage 'regardless' of the input level, so in this case provides a nice clean, consistent 12v supply whether the van is running at 12.9 or 13.8 or 14.4 or whatever spikes are going on.

In the context of the information above, a regulator is not essential at all - but given that suitable models (like the ones from REUK) are about a fiver, then it may make a lot of sense to protect your expensive LED light fittings by using these. Its a simple risk calculation, and I personally believe it makes sense to do it, but is entirely up to you.

Theres plenty of choice as to where to buy them from, here is just one link to a regulator I can reccomend having used it myself for some time: http://www.reuk.co.uk/buy-12-VOLT-RE...-WITH-FUSE.htm
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A 1 Amp (=1000mA) regulator like the one above will cope with most LED fittings. For example, a set of four IKEA Dioders only pull around 300-350mA when in use, for the whole set, without the regulator getting too warm. You could certainly add more LED fittings to a single 1A regulator, up to it's 1000mA limit, but it will get hot when running at full capacity - its probably better to run separate regulators for separate LED sets, and to consider mounting the regulator in a well ventilated space to help with cooling if running it at over 50% capacity. Larger regulators are another equally valid option.

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HOW to wire up your lights and regulator:


If you remove and unplug your existing interior light fitting you will be holding a connector with three wires.



One of the wires will be a permanent +12v supply (don’t let this come into contact with the van body)

One is a permanent 0v ‘earth’, so that the switch in the existing interior lights can complete the circuit and turn the light on.

One is a switched 0v ‘earth’, that only comes on when the doors are opened.

I have deliberately not color-coded the diagram or detailed which is which in the description, in case your van varies - always use a meter to test and work out which is which on your van first, and label them - it's an easy process to do this, any £5 multimeter will do for this purpose. If you need help with this just ask, its easy to talk you through it.

Using the permanent feed from the existing interior lights also means that all the fittings are still run from the correct fuse.

IF you are using a regulator from REUK then the following diagram will work (however the wiring principles are the same for any, they will have a connection for the INPUT feed from the van, and a connection for the regulated OUTPUT, though the negative (or Ov or earth) connection may be the same for both input and output)
*Note - this diagram applies to LED fittings that are designed for 12v as described above and already have appropriate resistors built in - such as IKEA dioders and most other LED fittings designed for ''12v' use, as described above.



This is what that regulator looks like in real life:



If you want to be able to STOP the LED fittings coming on when the doors are opened, as well as turn them on at will, then the following diagram will work:
*Note - this diagram applies to LED fittings that are designed for 12v as described above and already have appropriate resistors built in - such as IKEA dioders and most other LED fittings designed for ''12v' use, as described above.




IF you don't want to use a regulator, then the following diagram will work, basically leaving the regulator out of the circuit:
*Note - this diagram applies to LED fittings that are designed for 12v as described above and already have appropriate resistors built in - such as IKEA dioders and most other LED fittings designed for ''12v' use, as described above.



If you want to use plain LEDs (rather than fittings designed for 12v use that already have appropriate resistors in place) Then you can still follow the diagrams above, but you will need to put an appropriate sized resistor in line with each LED to limit the current, regardless of whether you use a regulator or not. In this circumstance it is essential that you know: a) the voltage drop across the the LED and b) the current limit for that LED, as these are essential for calculating the resistor size to use.

There is an excellent online calculator for this purpose at http://ledz.com/?p=zz.led.resistor.calculator which covers the typical arrangments for wiring them. If you look at this and are out of your depth, then its probably best to buy fittings designed for 12v with the resistors already in place such as IKEA dioders or the ones that Upspex sells.

I hope this is of use.. please let me know if I've missed anything key out, and I'll edit the post.

Regards

Ben
 

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Excellent post mate T:.

Just one minor observation, the diagram with the switch that disables the "door open" facility could have a 3 way switch as well in there, as some people may want to go down that route.
 

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finally i understand what im suppose to do! excellent post mate. STICKY!! :)
 

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Thanks for posting this i purchased some decking lights today ready to fit, i now know how T:
 

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Great postT:T:

I had a basic nderstanding, that just made it crystal clearT:T:

This is what forums are for........T:T:

Paul
 

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Discussion Starter #8
Is there / could there be a fire risk from not using a regulator?
LED fittings use less current than standard bulbs, so unlikely from a 'load' perspective.

If they pop due to over voltage and therefore too much current for the individual fitting, they go open circuit (like a fuse does), so no more energy being drawn - plus the amount of current required to do that to an average fitting is actually very small, so the heat produced if enough to make it pop is unlikely to be an issue.

I do think a regulator is a good idea for sure, but I'd hesitate to overplay it by saying there's a fire risk if you don't.

Plus - if you use the feed from the interior lights as shown in the diagrams, then it will all still be running from the van's existing interior lights fuse which will also protect the circuit.
 

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Excellent clear write-up!

I have also bought some decking led lights that come with a transformer to allow them to plug into a 240v supply.

Without the transformer they run on 12v but will each light fitting already have a resistor in place? I would assume that only a regulator is therefore required before fitting to the van?
 

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Question loosely based on this... What is the effect if the regulator fails? No voltage or unregulated voltage?

Putting a 5v regulator in to power usb and don't want to blow up phone/sat nav. Def. Using this for leds.

What about drl's? I assume just as important if they aren't regulated as I found out recently. Only issue may be weather proofing regulator.

Great post by the way.
 

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Discussion Starter #11
Excellent clear write-up!

I have also bought some decking led lights that come with a transformer to allow them to plug into a 240v supply.

Without the transformer they run on 12v but will each light fitting already have a resistor in place? I would assume that only a regulator is therefore required before fitting to the van?
Basically yes. if the output voltage from the transformer is 12v, then each 'fitting' will have the necessary resistor to limit the current as required for 12v operation.
 

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Discussion Starter #12
Question loosely based on this... What is the effect if the regulator fails? No voltage or unregulated voltage?

Putting a 5v regulator in to power usb and don't want to blow up phone/sat nav. Def. Using this for leds.

What about drl's? I assume just as important if they aren't regulated as I found out recently. Only issue may be weather proofing regulator.

Great post by the way.
Thank you..

Most regulators are designed to fail 'safe' - as in, no voltage rather than unregulated.

The principles described apply to all LEDs, however, the designers of DRLs are likely to have taken into account that pretty much by definition they will be running in vehicles with higher voltages floating around (at least lets hope so!) and chosen appropriate resistor values for that.. whereas the vast majority of LED lighting being fitted into vehicles are adaptions of fittings originally designed for a constant interior usage. Having said that, you're not going to hurt anything by fitting a regulator to protect DRLs - but I have no experience of them blowing to be able to actually say 'its worth doing'

hth

Ben
 

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Cool. I was thinking more of the home made 'drl' strips. I inherited these with my van and they were fine for two years until I did the headlight mod. They've started to fail quite quickly since!
 

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You will generally find that any LED product designed for automotive applications will be optimised at 14.5 volts so no regulator required. However, beware of the cheap and nasty!
 

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You will generally find that any LED product designed for automotive applications will be optimised at 14.5 volts so no regulator required. However, beware of the cheap and nasty!
I guess this also goes for led sidelight bulbs? I have got through a couple of these in the last year having unpllugged the capacitor (yellow plug) under the slam panel after installing my headlight upgrade loom. Cheap ebay bulbs may not have the correct resistor? The ones I used were basis led bulbs, now looking at smd options as these may have a resistor included....
 

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It isn't the resisitor that's the problem. It's cheap LEDs. If you get SMD ones then you stand a better chance of good quality.
 

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Discussion Starter #17
It isn't the resisitor that's the problem. It's cheap LEDs. If you get SMD ones then you stand a better chance of good quality.
You're right of course, cheaper fittings often use lower power LEDs that are already operating outside of their design range with inadequate current limiting, in order to get the desired amount of light out of them..

LEDs of a higher power rating cost more, and therefore better quality fittings are def. more likely to have a bigger safety margin, but even top quality LEDs still require the current to be appropriately limited - you'll still pop a good LED far quicker with too much current than a cheap one thats operating within it's safe current limit.
 

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Maybe there's a simple answer to this problem.

My mate has a car transporter and being law abiding wired it up with the appropriate LED's and marker lights.

It is plugged via the usual trailer socket to the back of a fairly new Land Rover Discovery, which, incidentally, has after-market LED lights.

All works well, except that the left-hand side indicator flashes all the time the lights are on. Just a quick pulse 3-4 times a second.

When switched to indicator via the column stalk both sides both sides work fine, as do the brake lights and rear lights.

Has a simple error been made?

Thanks for all replies.
 

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Maybe there's a simple answer to this problem.

My mate has a car transporter and being law abiding wired it up with the appropriate LED's and marker lights.

It is plugged via the usual trailer socket to the back of a fairly new Land Rover Discovery, which, incidentally, has after-market LED lights.

All works well, except that the left-hand side indicator flashes all the time the lights are on. Just a quick pulse 3-4 times a second.

When switched to indicator via the column stalk both sides both sides work fine, as do the brake lights and rear lights.

Has a simple error been made?

Thanks for all replies.
 

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Registered
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Maybe there's a simple answer to this problem.

My mate has a car transporter and being law abiding wired it up with the appropriate LED's and marker lights.

It is plugged via the usual trailer socket to the back of a fairly new Land Rover Discovery, which, incidentally, has after-market LED lights.

All works well, except that the left-hand side indicator flashes all the time the lights are on. Just a quick pulse 3-4 times a second.

When switched to indicator via the column stalk both sides both sides work fine, as do the brake lights and rear lights.

Has a simple error been made?

Thanks for all replies.
It's either been wired up to a psuedo earth or that's CAN data causing the LED's to pulse.
 
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