A low cost LED lamp for your anchor light - some test results

Adrian Jones said:
I wish.........this is the back of a red/white constant current LED lamp....where am I going wrong....... Maybe you can design me an equivalent with 4/5 transistors?
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So who designed it ?

No need for 4/5 - as I said ... 2 transistors = constant current source. There's really no need for ICs, coils etc. for such a simple application.

Why should I design anything for you ?



You and your guffawing friend (and presumbly your designer too) are what I have come to describe - during a long career in electronics - as "voltage-fixated". And you're not alone.

Tae a look at: http://projects.dimension-x.net/archives/66 where someone else who is "voltage-fixated" considers how LEDs should be driven.


Now let's turn to a professional. Here's an article by someone who is in the IC manufacturing business, so obviously thinks in those terms:


How to select the right white LED driver
Tony Armstrong, Linear Technology (in Electronics Weekly, 22 May 2008)

The growing adoption of LEDs as a lighting source in different applications has simultaneously driven the demand for LED driver ICs to power them.

To understand the obstacles for the design and manufacture of these LED driver ICs, it is necessary to understand what a white LED requires in order to produce light. A white LED must be driven by a constant current source so that the white point of the light does not shift (that is, it must be uniform).

Furthermore, since the white LED is a diode, its internal forward voltage (Vf) drop has to be overcome. This Vf varies with the current rating of the white LED and will also change with temperature. A typical 20mA white LED has a Vf that varies between 2.5V and 3.9V over the entire operating temperature range.



I will repeat - a simple (and therefore cheap) constant current source can be achieved with a simple 2-transistor circuit which - not being temperature stabilised - will, as a bonus, cause the output current to decrease by (typically) 0.3%/deg C., which I would not regard as being problematic, and would even serve as a modest safety feature.

Light temperature stability is certainly not an issue with an anchor light, and I suspect that complex designs have resulted from the desks of those designers who seek to tightly control light temperature stability for those applications where it does matter - such as display backlighting.
 
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We've been following this thread with interest as we are undecided on the merits of buying cheap LED bulbs having heard mixed reports, mostly bad! and its all gone quiet about the test lamp which looked promising, I think. Any results yet Bluechip from the cheap lamp? Has anyone else on here done the same test yet?


It would be interesting for us 'technically challenged' to keep up with this post,.... we are learning something new everyday! It would be good to see the test results for future reference and preferably in 'layman' terms with photos of ammeter and voltage readings, that picture of the test set-up was great.

I wait with 'baited' breathe for any 'enlightening' results?.....................where's the popcorn man?
 
Kate Smith said:
We've been following this thread with interest ..........its all gone quiet about the test lamp which looked promising, ..........
I wait with 'baited' breathe for any 'enlightening' results?.................
Click to expand...

The thread only started 4 days ago! I (and probably many others) have ordered the bulbs in question to experiment with, but delivery from China does take a few days :rolleyes:

I am sure some of us will comment on our findings - though probably in new threads.

Vic
 
can I ask ?, last year I eh acquired 5 strips of led's from a shop fridge lol,
and have been using them in my boat for the past year , should I be worried about them burning my boat to the water line, or just get on with it and ejoy the sunny weather up here in sunny loch lomond.
 
jimmcgee said:
can I ask ?, last year I eh acquired 5 strips of led's from a shop fridge lol,
and have been using them in my boat for the past year , should I be worried about them burning my boat to the water line, or just get on with it and ejoy the sunny weather up here in sunny loch lomond.
Click to expand...

I think you have to take a pragmatic view.
If you have the knowledge to understand the technical stuff you are doing that's fine. Its the knowledge gap that often bites you in the nether regions!
If electrical equipment is used in an environment its not designed for there are obvious risks. Items can and do overheat or the opposite can be true and devices can under perform. If its a garden light and it goes dim or overheats, so what. If its your anchor light that goes dim.....well the potential for trouble is fairly obvious.
I would suggest you satisfy yourself that your strips of LEDs are safe. Or you replace them with a product from a reputable supplier who offers you a reasonable warranty.
Regards
 
Kate Smith said:
We've been following this thread with interest as we are undecided on the merits of buying cheap LED bulbs having heard mixed reports, mostly bad! and its all gone quiet about the test lamp which looked promising, I think. Any results yet Bluechip from the cheap lamp? Has anyone else on here done the same test yet?
Click to expand...

Sorry for not getting back. I ran the lamp at the overvoltage settings I showed in the picture for 24 hours, it was still burning (not literally) brightly when SWMBO wanted her dining room table back and I had to stop the test.
There is no question in my mind that this lamp will not catch fire or melt or the diodes will not drop off the board regardless how long the test was run for.

I am now back on my boat and have bought the anchor light with me, I had planned to take some pics 'at anchor' and try and show the comparative brightness with other anchor lights, but the weather has been so horrible that we haven't left the marina.
Maybe tomorrow?

I have some 18 LED lamps on board that I use for interior lighting, none of them with the exception of some really powerful single LED, halogen spot light bulb replacements cost more than a couple of pounds each.

As I write this my boat battery is charging and the voltmeter is reading 13.33V. I fitted these LED's last winter and they must have run for 250 hours or more with no signs of any failure. These lamps were so cheap that I bought a few spares, so even if I did get a failure it wouldn't worry me, though if one caught fire that would be a different matter.

To satisfy myself that these interior lamps are safe I'll take one home and run it at the high overvoltage for an extended period and report back.

I am not expecting a problem.

As an aside if anyone uses spotlights with 20W halogen bulbs for reading I cannot recommend highly enough these LED spots bulbs - http://www.ebay.co.uk/itm/4-X-MR11-...6627129?pt=UK_Light_Bulbs&hash=item27babc4cb9, the light output is amazing and the current consumption just a miserly 1W
 
Adrian Jones said:
I think you have to take a pragmatic view.
If you have the knowledge to understand the technical stuff you are doing that's fine. Its the knowledge gap that often bites you in the nether regions!
If electrical equipment is used in an environment its not designed for there are obvious risks. Items can and do overheat or the opposite can be true and devices can under perform. If its a garden light and it goes dim or overheats, so what. If its your anchor light that goes dim.....well the potential for trouble is fairly obvious.
I would suggest you satisfy yourself that your strips of LEDs are safe. Or you replace them with a product from a reputable supplier who offers you a reasonable warranty.
Regards
Click to expand...

most of that went right over my head , I’m a Scotsman , from paisley , were they invented copper wire , cos 2 of us were fighting over a 1 pence lol,

I wired the led strips with a length of wire and a fuse and stuck them on the battery, and they have done their job for the last year, all that other stuff up there is too high tec for me!!.
 
electrosys said:
... as I said ... 2 transistors = constant current source. There's really no need for ICs, coils etc. for such a simple application...
Click to expand...

You are quite right, it is indeed possible to create a constant current source with a couple of transistors and a few simple components. But what you fail to understand is that this will be a constant current source that it severely limited in voltage range - perhaps enough to drive only 2 LEDs. Therefore you have to repeat this "simple" circuit for every pair of LEDs that you use.

In order to drive the number of LEDs required in a navigation or anchor light, you either have to have a couple of dozen such current sources, or do it the right way with a PWM Buck converter. This boosts the original 12V to a much higher level, then rapidly switches the LEDs on or off to keep the average drive current correct.
 
As an aside if anyone uses spotlights with 20W halogen bulbs for reading I cannot recommend highly enough these LED spots bulbs - http://www.ebay.co.uk/itm/4-X-MR11-G...item27babc4cb9, the light output is amazing and the current consumption just a miserly 1W

It really amazed me too...360 Lumens for a 1W LED according to the link posted.

CREE, pretty much the worlds leading LED manufacturer, in the USA, announced in May 2011 that they had just managed to get a record output of 231 Lumens from a 1W LED lamp.

I don't know what else to say!
 
BlueChip said:
Sorry for not getting back. I ran the lamp at the overvoltage settings I showed in the picture for 24 hours, it was still burning (not literally) brightly when SWMBO wanted her dining room table back and I had to stop the test.
There is no question in my mind that this lamp will not catch fire or melt or the diodes will not drop off the board regardless how long the test was run for.

I am now back on my boat and have bought the anchor light with me, I had planned to take some pics 'at anchor' and try and show the comparative brightness with other anchor lights, but the weather has been so horrible that we haven't left the marina.
Maybe tomorrow?

I have some 18 LED lamps on board that I use for interior lighting, none of them with the exception of some really powerful single LED, halogen spot light bulb replacements cost more than a couple of pounds each.

As I write this my boat battery is charging and the voltmeter is reading 13.33V. I fitted these LED's last winter and they must have run for 250 hours or more with no signs of any failure. These lamps were so cheap that I bought a few spares, so even if I did get a failure it wouldn't worry me, though if one caught fire that would be a different matter.

To satisfy myself that these interior lamps are safe I'll take one home and run it at the high overvoltage for an extended period and report back.

I am not expecting a problem.

As an aside if anyone uses spotlights with 20W halogen bulbs for reading I cannot recommend highly enough these LED spots bulbs - http://www.ebay.co.uk/itm/4-X-MR11-...6627129?pt=UK_Light_Bulbs&hash=item27babc4cb9, the light output is amazing and the current consumption just a miserly 1W
Click to expand...

Lets try again link went wonky! So lets use Bluechips's Original

It really amazed me too...360 Lumens for a 1W LED according to the link posted.

CREE, pretty much the worlds leading LED manufacturer, in the USA, announced in May 2011 that they had just managed to get a record output of 231 Lumens from a 1W LED lamp.

I don't know what else to say!
 
BlueChip said:
Sorry for not getting back. I ran the lamp at the overvoltage settings I showed in the picture for 24 hours, it was still burning (not literally) brightly when SWMBO wanted her dining room table back and I had to stop the test.
There is no question in my mind that this lamp will not catch fire or melt or the diodes will not drop off the board regardless how long the test was run for.

I am now back on my boat and have bought the anchor light with me, I had planned to take some pics 'at anchor' and try and show the comparative brightness with other anchor lights, but the weather has been so horrible that we haven't left the marina.
Maybe tomorrow?

I have some 18 LED lamps on board that I use for interior lighting, none of them with the exception of some really powerful single LED, halogen spot light bulb replacements cost more than a couple of pounds each.

As I write this my boat battery is charging and the voltmeter is reading 13.33V. I fitted these LED's last winter and they must have run for 250 hours or more with no signs of any failure. These lamps were so cheap that I bought a few spares, so even if I did get a failure it wouldn't worry me, though if one caught fire that would be a different matter.

To satisfy myself that these interior lamps are safe I'll take one home and run it at the high overvoltage for an extended period and report back.

I am not expecting a problem.

As an aside if anyone uses spotlights with 20W halogen bulbs for reading I cannot recommend highly enough these LED spots bulbs - http://www.ebay.co.uk/itm/4-X-MR11-...6627129?pt=UK_Light_Bulbs&hash=item27babc4cb9, the light output is amazing and the current consumption just a miserly 1W
Click to expand...

At this point to be absolutely fair I must suggest that your experiment is no more valid than the U tube fire. Neither would have goy past my product safety chaps back when I was a wage slave
 
And its been informative.

We have learned ( and I certainly wasnt aware beforehand) that there are two types of led bulbs, resistor controlled and current controlled. We have learned that there can be a fire risk with some resistance controlled lights and how do you tell which are a risk and which arent before you buy? We also now know that resistance controlled bulbs use extra leccy at high voltages and thus negate part of the reason for buying leds ie leccy saving. And lastly we have learned that there are plausible reasons for the current controlled jobbies being a lot more expensive than the cheapo ebay resistance controlled jobbies.

I've been converted. For the sake of the small extra cost involved I will use current controlled leds to be sure I'm not going to set fire to my boat. And since he has brought the whole matter to light and responded politely and well to our usual forum harassment, I will buy mine from Adrian. I suggest the rest of you cheaseparers do so too! Cant say fairer than that
 
Thank you

Bosun Higgs said:
And its been informative.

We have learned ( and I certainly wasnt aware beforehand) that there are two types of led bulbs, resistor controlled and current controlled. We have learned that there can be a fire risk with some resistance controlled lights and how do you tell which are a risk and which arent before you buy? We also now know that resistance controlled bulbs use extra leccy at high voltages and thus negate part of the reason for buying leds ie leccy saving. And lastly we have learned that there are plausible reasons for the current controlled jobbies being a lot more expensive than the cheapo ebay resistance controlled jobbies.

I've been converted. For the sake of the small extra cost involved I will use current controlled leds to be sure I'm not going to set fire to my boat. And since he has brought the whole matter to light and responded politely and well to our usual forum harassment, I will buy mine from Adrian. I suggest the rest of you cheaseparers do so too! Cant say fairer than that
Click to expand...

Thank you for that, I will now remove the pins from the Nija Doll that has your name on it...ha.

In case folks are interested I have posted some detailed general advice on another thread started by Kate Smith on this forum. Kate has asked for some advice on what to look for when selecting LED lighting for use on boats.
I think others might be interested and apologies in advance if it repeats a little of what has been said here. (practice makes perfect!)
 
An anchor light does not have to be seen from miles away like Nav lights. A hundred years ago we would be taking about a paraffin lamp with a light output of about 50 lumens.

So a low cost Led which pumps out 100-150 lumens, and which draws a fraction of an amp seems to be better than the present 2.5 amp tungsten bulb
 
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