LED stick on strip lights - transformer?

[Odana]

Having admired the Moomin Papas' cabin lighting, I want to fit various lengths of LED strip under our gunwales

 

3 questions:

• Can I wire this straight into an extension off the 12v lighting circuit, or do I need the transformer of other kit that seems to be sold with it for landlubbers?
• What are typical switching arrangements (use simple language please - I am electrically challenged..)
• Are there any suppliers recommended or to avoid?

Anything else I need to know before I go back to browsing ebay?

 

Thanks!!

 

[Kwacker]

I got mine here

http://stores.ebay.co.uk/navibuzz/

Wired via a fuse straight off 12v ...... The transformer is for use with 230v

I bought 4 of the 5m RGB 5050 with remote control, 2 for each gunwale in the saloon, and 1 For the bedroom.

They have transformed the boat after sunset.

[bottle]

Just be aware of the voltage, perhaps a 'regulator' would be a good idea, they may not like the higher voltages of a boat.

[Nickhlx]

I have also been experimenting with these 5M tapes.. one of the ads said they were "suitable for car use", which I took as "they are OK to use up to 14.4 volts". The ones I have say they are nominally "12 volts 72 watts", and whilst the transformers that come with them is 12.0 to 12.5 volts, they only take approx 2.5 to 3 amps at this voltage, which is half the claimed drain / dissipation.

 

Putting them on the bench and feeding off a regulated Power Supply, they do rise in current draw (as expected) as tabulated below - the other thing I measured was the voltage appearing at the other end, as along 5 mtrs of quite thin strip I expected quite a drop... The results below were obtained by feeding from one end only, which does make those nearest the feed a little brighter than those at the other end

 

Supply Current Power Voltage Voltage

Voltage drawn (watts) at end Drop

 

12.0 2.60 31.2 9.85 2.15

12.5 2.95 36.9 9.98 2.52

13.0 3.36 43.7 10.17 2.83

13.5 3.73 50.4 10.33 3.17

14.0 4.10 57.4 10.49 3.59

14.5 4.50 65.2 10.64 3.86 all tested on a 5M strip

 

To maintain less of a voltage drop between the ends, the strip could be fed in the middle, if you have a soldering iron, or some twin cable connected / soldered to each end ( observing polarity !) and this fed in the middle. However, even this significant voltage drop didn't seem to produce that much of a difference in brightness... they do get quite warm, and as life is partly a function of operating temp, perhaps it would be preferred to keep the voltage down to nearer the "rated" 12.0 volts - interesting they produce "similar" brightness though down to around 10 volts... then brightness drops off steeply at 9.0 volts (0.5 A) and they extinguish at about 7.6 volts. I was quite surprised at the range of voltage they worked over...

Certainly they would function well as a dimmable light source by simply feeding with variable voltage, and modules to do this are readily available off E-Bay for minimal outlay - they should have a 5A capability though to handle the current at the higher supply voltages. An inexpensive "dimmer" could be in the form of (a) suitable ( 5A) diode(s) in series with the supply, which will each drop around 0.5 to 0.8 volts, or if you want to limit the max voltage you expose them to.

 

I haven't run these off a vehicle supply yet, so have no feel for how sensitive they are to the normal vehicle spikes, but if people begin reporting leds failing, then I guess they will need a bit of filtering

 

Hope the constructors amongst us find that helpful / interesting

 

Nick

Edited January 10, 2015 by Nickhlx

[Jambo]

Very helpful nick. Can you link to some examples of these variable voltage modules? I've had a look around eBay and can see some things that might be what you mean but I'm not sure.

[nicknorman]

We have RGB LED tape under the gunnels in saloon & dinette area, run from a controller, but also strips of warm white tape in the glass cupboard and under the galley worktop, running direct off the boat's 12v supply. After nearly 4 years, no failures so it seems fairly tolerant of higher voltages and spikes.

Edited January 10, 2015 by nicknorman

[nicknorman]

Anything else I need to know before I go back to browsing ebay?

 

Thanks!!

 

I would avoid the old-fashioned type with wired round LEDs, instead go for surface mount type (SMD). The choice is then about colour -go for warm white, or RGB + controller if you like (more expensive, but worth it for "mood lighting"). You can get vaious sizes/power output of LEDs at vaious different spacing (LEDs per metre etc). I would go for close spacing (ie plenty of LEDs /metre) but relatively low power, so as to give an even light without using too much power.

 

If you are just going for white, consider a PWM dimmer as these tapes can be quite bright and certainly stand some (power saving) dimming of a cozy evening.

Edited January 10, 2015 by nicknorman

[Odana]

Thanks all. Do the RGB ones have white as one of the options? Looking at n screen they just seem to be the three colors and I definitely don't need red or green or blue lighting!

 

Is there any particular kind of switch 12v needs or can I just buy any switches? Now I've got to browsing I am thinking of all sorts of places to put these - like inside wardrobes and kitchen cupboards. Cheap movement sensor switches would by good, but maybe I should not be too ambitious and just stick w my battery lights there for now..

[adrianh]

I have been experimenting with these in both warm white and rgb.

The rgb does not go white but gives a good range of colours.

I also have done the bench test and was suprised at the rise in current as the voltage rises and the significant temperature rise of the leds.

I have decided to fit local voltage regulation for these or possibly a voltage regulator in the supply to my lighting circuits if I can find/build something suitable.

Looking at the constuction and the possible fire risk if these tapes fail, I am also going to fit inline quick blow fuses to match each installed length at the point where the wiring reduces size (ie 4 amps max).

I have seen the consequences of short at the end of a low voltage /high current source cable - think glow plug!

[nicknorman]

Thanks all. Do the RGB ones have white as one of the options? Looking at n screen they just seem to be the three colors and I definitely don't need red or green or blue lighting!

To get "white" on your TV screen, it mixes red, green and blue light. This look like white light to the human eye. For the RGB tape the gamut is perhaps not to pure white light, but certainly a warm white light reminiscent of an incandescent (ie ordinary) light bulb. Controllers come in different flavours but with ours we can adjust the levels of red, blue and green independently to get pretty much any colour. An orange fire-glow colour for cold winter nights snuggled up in front of the fire. A bright purple for watching Strictly! And warm white for "normal". The controllers normally do some sort of fading through various colours function which is good for taking hallucinogenic drugs but can otherwise get a bit irritating after a while!

Is there any particular kind of switch 12v needs or can I just buy any switches? Now I've got to browsing I am thinking of all sorts of places to put these - like inside wardrobes and kitchen cupboards. Cheap movement sensor switches would by good, but maybe I should not be too ambitious and just stick w my battery lights there for now..

Any old switch that you might use to control 12v lighting. Just make sure the switch's current rating at DC exceeds the drain from the LEDs - which of course depends on the length of the strip. The currents involved are fairly low. For cupboards, perhaps a door switch would be better than a movement switch?

Edited January 10, 2015 by nicknorman

[MoominPapa]

If you're planning to use the "buy it by the metre" LED tape, then it does need some sort of regulator to run from a 12v system. I used LM2940 regulator chips on aluminium heatsinks. Despite the scepticism from the engineers on this thread: http://www.canalworld.net/forums/index.php?showtopic=40954 it worked fine, and continues to do so four years later. An LM2940 is good for about 1 metre, possibly a bit more. Each of the individually switchable strips on Melaleuca has its own regulator.

 

This isn't really a plug-and-play solution if you're not good with electrics, but I'll happily talk you through the details if you want to give it a go. All the bits are available from Maplins.

 

MP.

Edited January 10, 2015 by MoominPapa

[Nickhlx]

The LM 2940 is a low drop out voltage regulator ( typically 0.5 volts at 1 A ) but it will only supply a max of about 1A (with some heatsinking). It is intended for vehicular applications, and has some anti-static protection built in.

 

Lower voltage dropout can be achieved using Power FETs, but needlessly complex for this sort of non-critical application .

 

Nick

[nicknorman]

If you're planning to use the "buy it by the metre" LED tape, then it does need some sort of regulator to run from a 12v system. I used LM2940 regulator chips on aluminium heatsinks. Despite the scepticism from the engineers on this thread: http://www.canalworld.net/forums/index.php?showtopic=40954 it worked fine, and continues to do so four years later. An LM2940 is good for about 1 metre, possibly a bit more. Each of the individually switchable strips on Melaleuca has its own regulator.

 

This isn't really a plug-and-play solution if you're not good with electrics, but I'll happily talk you through the details if you want to give it a go. All the bits are available from Maplins.

 

MP.

My LED tape has worked fine without any regulation for 4 years. We often cruise with the under-gunnel lights on when it's gloomy outside, with system voltage 14.6v or so. I'll admit it check they are off before doing an equalise at 15.5v.

 

I bought a bunch of regulators / heatsink but never uninstalled them.

Edited January 10, 2015 by nicknorman

[MoominPapa]

My LED tape has worked fine without any regulation for 4 years. We often cruise with the under-gunnel lights on when it's gloomy outside, with system voltage 14.6v or so. I'll admit it check they are off before doing an equalise at 15.5v.

 

I bought a bunch of regulators / heatsink but never uninstalled them.

Interesting. It would be very interesting to know how much the current increases between V=12 and V=14.6

 

MP.

[Nickhlx]

See table above for a 5M strip ...

 

At 12.0 volts the current was 2.6A

and

at 14.5 volts the current was 4.5A

 

so approaching double

 

Nick

[nicknorman]

Interesting. It would be very interesting to know how much the current increases between V=12 and V=14.6

 

MP.

I haven't measured it but at 14.6v the chips don't get hot, just warm (ie not too hot to touch). Maybe it depends on the specific tape, although none seem to be regulated.

[Odana]

Now you're all starting to speak foreign around me! Electrician stepson will fit it all when he comes to do a bunch of other stuff here, but I need to decide and buy the bits first. Mr Moomin' - I may well need to give you a call with my shortlist. After all it was your lovely boat wot started all this pondering !!

Now you're all starting to speak foreign around me! Electrician stepson will fit it all when he comes to do a bunch of other stuff here, but I need to decide and buy the bits first. Mr Moomin' - I may well need to give you a call with my shortlist. After all it was your lovely boat wot started all this pondering !!

[nicknorman]

See table above for a 5M strip ...

 

At 12.0 volts the current was 2.6A

and

at 14.5 volts the current was 4.5A

 

so approaching double

 

Nick

It must depend on the particular design of tape though. With that much of an increase in current you would surely expect a big change in brightness, but I don't see any significant difference engine on vs off. We are on the boat next w/e, I'll try to remember to check it out.

[MoominPapa]

It must depend on the particular design of tape though. With that much of an increase in current you would surely expect a big change in brightness, but I don't see any significant difference engine on vs off. We are on the boat next w/e, I'll try to remember to check it out.

 

The power dissipation increases faster in the resistors than the LEDs. Simplifying, and assuming that the LED forward voltage is fixed at 3v per LED (three in series) then at 12V there's 3v across the resistor, whilst at 15V there's 6V across the resistor, which is why the current doubles. The power dissipation in the resistor therefore goes up four times (!) (twice the current and twice the voltage).

 

 

MP.

[Nickhlx]

Very helpful nick. Can you link to some examples of these variable voltage modules? I've had a look around eBay and can see some things that might be what you mean but I'm not sure.

 

Yes - this one takes battery volts and drops to your preferred voltage, taking up to 1.5 volts to do its stuff, depending on current drain - good for a conservative 2A which is probably most of a 5M strip at 12 volts...

 

http://www.ebay.co.uk/itm/LM2596-Step-down-Power-Module-DC-Adjustable-LED-Voltmeter-UK-/351214656892?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item51c6065d7c, and cheaper if you get one

without the voltmeter

 

 

or this one for more power http://www.ebay.co.uk/itm/5A-DC-DC-Adjustable-Step-down-Module-A-Voltmeter-Efficiency-With-Free-Pillars-/271597871387?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item3f3c7ea11b

 

Nick

I do think it is compromising reliability if you run them much above about 13 volts, unless stuck to cold metal, where you could maybe go a touch higher...

 

The brightness difference isn't that great unless you switch between the different voltages whilst looking at them

 

Nick

[nicknorman]

The power dissipation increases faster in the resistors than the LEDs. Simplifying, and assuming that the LED forward voltage is fixed at 3v per LED (three in series) then at 12V there's 3v across the resistor, whilst at 15V there's 6V across the resistor, which is why the current doubles. The power dissipation in the resistor therefore goes up four times (!) (twice the current and twice the voltage).

 

 

MP.

Yes I understand and agree with all that, but the consequence depends on the rating of the resistors (ie whether they can take the increased dissipation) and also the ratio of LEDs to resistance in a string. You are saying 3 LEDs but is that the case for all tapes?

 

All I can say is that I bought the regulators based on my own analysis as per your above, but found that the reality was that they weren't necessary. I'll check but I don't think the current goes up that much (maybe there are fewer LEDs in series, although of course that would be less efficient).

Yes - this one takes battery volts and drops to your preferred voltage, taking up to 1.5 volts to do its stuff, depending on current drain - good for a conservative 2A which is probably most of a 5M strip at 12 volts...

 

http://www.ebay.co.uk/itm/LM2596-Step-down-Power-Module-DC-Adjustable-LED-Voltmeter-UK-/351214656892?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item51c6065d7c, and cheaper if you get one

without the voltmeter

 

 

or this one for more power http://www.ebay.co.uk/itm/5A-DC-DC-Adjustable-Step-down-Module-A-Voltmeter-Efficiency-With-Free-Pillars-/271597871387?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item3f3c7ea11b

 

NickI do think it is compromising reliability if you run them much above about 13 volts, unless stuck to cold metal, where you could maybe go a touch higher...

 

The brightness difference isn't that great unless you switch between the different voltages whilst looking at them

 

Nick

Well all I can say is 4 years, many many hours running at 14.4 to 14.6v, they don't get that hot, and no failures yet. The RGB ones are mounted on the bottom of some plastic trunking, but then maybe the RGB controller reduces the voltage a bit. The warm white stuff is stuck to wood inside a glass cupboard, or the underneath of the worktops (which are just dense chipboard type laminated worktops). Being under a worktop is I'm sure not the best place for convective cooling. Edited January 10, 2015 by nicknorman

[MoominPapa]

Yes I understand and agree with all that, but the consequence depends on the rating of the resistors (ie whether they can take the increased dissipation) and also the ratio of LEDs to resistance in a string. You are saying 3 LEDs but is that the case for all tapes?

It's the case for all the tapes I've seen. The forward voltage of the LEDs depends on the band-gap of the semiconductor so that sets the maximum number, since forward voltage times string length has to be comfortably less then minimum supply voltage. The trade-off is between stability of current/voltage and efficiency. One higher value resistor per LED will allow a lower minimum supply and have a much slower rise in current as the supply increases, but far more power will be wasted in the resistor. It looks like three LEDs per string is the best compromise for 12v systems.

 

All I can say is that I bought the regulators based on my own analysis as per your above, but found that the reality was that they weren't necessary. I'll check but I don't think the current goes up that much (maybe there are fewer LEDs in series, although of course that would be less efficient).

Well all I can say is 4 years, many many hours running at 14.4 to 14.6v, they don't get that hot, and no failures yet. The RGB ones are mounted on the bottom of some plastic trunking, but then maybe the RGB controller reduces the voltage a bit. The warm white stuff is stuck to wood inside a glass cupboard, or the underneath of the worktops (which are just dense chipboard type laminated worktops). Being under a worktop is I'm sure not the best place for convective cooling.

Which is very useful information. I'm entertained how much it contrasts with the predictions of doom from the EEs in 2011.

 

MP

Now you're all starting to speak foreign around me! Electrician stepson will fit it all when he comes to do a bunch of other stuff here, but I need to decide and buy the bits first. Mr Moomin' - I may well need to give you a call with my shortlist. After all it was your lovely boat wot started all this pondering !!

Feel absolutely free to call or PM me. Happy to help.

 

MP.

[nicknorman]

... I'm entertained how much it contrasts with the predictions of doom from the EEs in 2011.

I was probably one of those EEs! The principle you mention is undoubtedly sound (ie a disproportionate increase in power consumption for a relatively small increase in voltage) but in the real world, whether or not this is an issue depends on the overhead designed into the resistors' power rating.

[nicknorman]

Just to follow up, down on the boat this weekend so I checked a 1.4 metre section of warm white tape under the galley worktop. Disconnecting the mains got the voltage down to 13.2, at which the current was 0.85A. When I cranked the combi up to 14.8v it went up to 1.3A. So a 50% increase in current for a 12% increase in voltage, which is pretty much what we would expect. However after quite a while, the tiny SMD resistors (one per 3 LEDs) were not too hot to touch, maybe at 50-55 deg C. I think this is because the copper tape acts as a pretty good heatsink. The LEDs themselves were only warm, maybe 40 deg C. At those sort of operating temperatures I don't think reliability will be significantly compromised. And 14.8v is higher than most folk's charging goes. Boat ambient temperature was 22 degrees.

[Sea Dog]

According to the table posted earlier by nickhix, for a 5m 5050 LED strip (12v 75w) we're looking in the range of 30w-65w load with increasing voltage and nicknorman's figures above seem to bear that out. My LED main cabin lights are 6 x 3w downlighters and the space is very well lit by them. If that (nominal) 18w does that, I can't see that these 5m 5050 strips, which are essentially mood lighting, are worth the tariff. Maybe 3528 strips may be better? Or the perhaps small individual recessed lights?

 

I like the idea so I'm not trying to raise a spoiler here, just wondering if it's worth exploring the more battery friendly options.