ok, so how do i switch it on at night only ?

simonfraser

simonfraser

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i have plenty of solar panels to supply the led anchor light, but, of course i only wnat it on at night.
checked the web for light sensitive switches, i.e. switch the anchor light on at night. these all include a relay, haha that uses more mA's than it saves. might as well leave it on 24/7.
some one must make / supply a kit without a power sucking relay ????
 
Surely these prolific and IMHO revolting garden solar lights must have something you can use? They ony come on at night (to keep an eye on the gnomes).
 
An electronic photo switch need only draw a milliamp or so but I don't know who sells one. Do Maplins sell one? It would make a nice little project for an electronics hobby enthusiast. Are you sure that the relay ones draw a high current when off as well as when on?
 
A circuit like this one:
tranldr1.gif

will switch a small load - costs about 50p in components. To switch a higher load you could use a Darlington pair instead of just the one transistor:
darlingt.gif
.
The Rapid Electronics catologue has many circuits hidden in its pages, and this plus a decent school technology book at GCSE level should make it fairly easy to make a control circuit for an LED anchor light.
 
[ QUOTE ]
Do Maplins sell one?

[/ QUOTE ] Maplins indeed do sell a light sensitive switch, QP97F, but it incorporates a relay. There is no technical bumph in the catalogue so cannot tell what current the relay draws. It might form the basis of a unit by removing the relay and driving an LED cluster directly but it might need an additional, or sustitute, power output transistor to drive a sufficiently powerful LED based bulb. Not my field of expertise I'm afraid.
 
There used to to be one on the market, sold for anchor lights. have a leaflet somewhere.
You can modify a garden light one, just allow for voltage.
There used to be a light sensative chip, done a quick check that looks dead now.
We make a light sensative switch, mosfet drive, milliamp cosumption, problem cost, unless you can make 1,000's in China, there not cheap. Tend to be for commercial craft.

Brian
 
[ QUOTE ]
A circuit like this one:

[/ QUOTE ] That will drive a "standard" LED that requires about 25mA. Don't know about the Darlington pair.

Ideally you want something that swtiches off again at a sightly higher light level than it swtiches on so that it does not flicker on and off at dawn an dusk but I guess that's not vital for this application.
 
I haven't got any books to hand at the moment, but I think that the first circuit shown above will have a current gain of around 80, and the second will be around 1000. So, using your figure of 25mA, a Darlington pair should be able to switch about 0.25 amps. I know they can be used to control a little dc motor, so maybe they can do a bit more than that. Maybe just enough for a 3 - 5 watt led cluster. A low power relay will allow it to switch a greater load but shouldn't increase the total power consumption by all that much (compared with leaving it on 24 hrs a day, or compared with using filament lamps).
 
I have looked a little deeper at the Maplin device. It is a Vellman MK125 and that has a relay, VR15M121C, with contacts rated at 15amps at 28volts DC and a 12volt 360 ohm coil. Its total power consumption is given as 100mA. Presumably when OFF you can deduct the 33mA coil current from that.
That means that the daytime current consumption will be about 67mA and the nightime power consumption will be 100mA plus the current required by the light.

The relay is unnecessarily rated at 15amps but swapping it for a smaller one will not make a great saving in total power consumption, the 33mA that the relay coil requires could be halved perhaps.

A 2nm visibility white LED cluster from Doctor LED will have a current consumption of ~100mA. A similar unit from Ultraleds, with a claimed 3nm visibility, also draws 100mA.

So using the light sensitive switch from Maplin and an LED cluster from either Doctor LED or Ultraleds you are looking at a nightime power consumption of 200mA and a daytime consumption of about 67mA.
 
Yes, well done, that's the general idea. There are chips on the market which are able to distinguish, with some success, between the approach of dusk and clouds. It might be worth checking the power drain. Some are (or used to be) operated at 230V straight from a street lamp supply and would be useless for this but I think there are others.

There isn't a huge need to worry about the gain of the transistor (or transistor pair) as that only passes current when switched on. The problem with a Darlington is susceptibility to noise and self-oscillation. The drive could be arranged as an emitter-follower which would lose 0.6V - no real problem - but all the drive current would be usefully used by the lamp.

I'm assuming (with all this high efficiency in mind) that we are talking about a high quality LED array designed to meet the Col Regs and pulsed internally. These could potentially cause radio frequency interference, not a problem at anchor on the Orwell out of season but a real pain at anchor when trying to pick up a weatherfax or RTTY. It is worth making sure that the chosen LED array does not cause RFI at the end of a 25m cable. Another point about the LED arrays is tolerance to voltage changes. The best arrays have an on-board voltage regulator so at 14.5V you are not reducing the life of the LEDs. Some may not have a regulator, so check the specified voltage range.

It you are driving the LED array from an electronic switch, the switch must be capable of giving the peak current drawn by the array. For RFI reasons there should be smoothing in the array module but if not, the drive to the transistor, if run as you have shown (common-emitter) needs to be sufficient to drive the peak current required by the LED array. This could be 100 times the mean current, or more, if the array is not smoothed, so do check and don't buy an unsmoothed array.

There is a potential for a dissapointment after spending a lot of time getting this set up. In any case, before wiring to the masthead, check it at grouind level!
 
vics, thanks, that is v. usefull, the maplin device will drive the relay, the coil uses 33mA, or 0.033 A ?
the triton anchor light uses 0.09.
so, can one remove the coil and solder the anchor light on directly ?
it would save a bit of power, but not a lot.
at any rate i do have the spare capacity in my solar charging panels to keep them both running 24/7.
 
I have replaced my anchor light bulb with an LED anchor light that incorporates a daylight sensor. Its made by FirstStar in the USA. Its very bright and can be tested before you fit it to the masthead with a 9v PP9 battery (in a darkened cupboard).
 
Or you can go the easy way and get one of the Davis anchor lights that incorporates a fresnel lens and its own relay - see http://www.davisnet.com/Marine/products/marine_product.asp?pnum=03300 (I'm sorry I don't know how to do the clever insertion thingy so you'll have to cut and paste.) We went with one of these after sharing a very windy anchorage in Camarinas with Beebopaloola, and seeing how v well it worked, and we love it!

Tarian's set up sounds interesting too.
 
An LED array is a better technique than a small tungsten with a lens for this purpose. For an anchor light you are really looking for an omnidirectional transmission, in azimuth and elevation.

The Fresnel lens (which is commonly used in lighthouses, etc.) works by refracting the light that would have gone up skyward, or down seaward, along a horizontal line, level with the sea. If this is mounted high up the lens is worse than useless unless the boat is moving a lot, in which case you'd have a twinkling light - not really what you want in an anchorage where you will be getting very close to the source.
 
[ QUOTE ]
The Fresnel lens (which is commonly used in lighthouses, etc.) works by refracting the light that would have gone up skyward, or down seaward, along a horizontal line, level with the sea. If this is mounted high up the lens is worse than useless unless the boat is moving a lot, in which case you'd have a twinkling light - not really what you want in an anchorage where you will be getting very close to the source.

[/ QUOTE ]
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You will find that most (probably all) quality navigation lights using tungsten bulbs claim to use fresnel lenses, including all round lights for anchoring. So the Davis one in the poster's link is in very good company.

Or are you suggesting that we should replace all of our own existing very expensive fresnel ones if we want to be seen? - if so please give some suggestions as to what with.
 
I think you need to understand a bit more about the technology, it isn't very complicated. "A Fresnel lens" is not sufficient description to define the product. There are varying designs and varying strengths. The purpose of these lenses is to concentrate more of the useful output into the direction you want, not the direction you don't want.

navlights.jpg


Sorry the picture is crap...I did it quickly with my tablet and Paint but I hope it helps to illustrate the point.

The stronger the lens the less the power transmitted above (and below, in symmetrical designs) the horizontal. Let's consider a nav light at 2m height, probably quite typical for a sailing yacht. The maximum brightness is along the centre-line, and this decreases the higher the eye goes from the centre-line. So the bridge watch on a commercial vessel, some 20m above sea level, might only see a dull twinkling. Not good.

Similarly, if you put a strong Fresnel on top of a mast, nearby vessels at sea level will not see a bright light.

The Davis lamp, from the published information, seems to have a very low power tungsten bulb so the actual light energy being given out in lumens is low. They seem to be using a Fresnel lens to concentrate that low energy to make it bright enough to be visible from a distance; this can only be by sacrificing angle of view.

LEDs, however, produce more lumens per Watt so you can get an improvement in brightness and visibility without being unduly focused on the horizontal - you might still use a Fresnel lens, but it doesn't need to be as powerful.

However, not all LEDs are designed to meet the Col Regs or function across the entire voltage range of a yacht (10.5V to 14.8V) so you need to choose carefully particularly in this emerging technology (high brightness LEDs for nav lights is still an emerging technology).
 
[ QUOTE ]
so, can one remove the coil and solder the anchor light on directly ?


[/ QUOTE ] I don't think you can assume that you can substitute a light assembly requiring 90mA for a relay coil which only requires 33mA . The manual and the circuit diagram for the unit sold by Maplin is on the Vellman website at http://www.velleman.be/downloads/0/manual_mk125.pdf What you can or cannot do depends on the characteristics of the transistor T1. I have no information on that. If that transistor will not pass a current of 90mA it would no doubt be possible to replace it with a suitable one that will. Again that is not something I can help with.

An alternative would be to retain the existing transistor and fit a relay with a higher resistance coil. I think I remember seeing one in the Maplin catalogue with a 12volt 720 ohm coil but still with contacts more than adequately rated for the light in question.
 
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