Anyone tried building a frankenbebi anchor light?

Rigger Mortice said:
Design flaw number two. :D

Those LED's have a viewing angle of only 15 degrees. With 15 LEDS full 360 degree coverage will be poor. It certainly won't be as bright from all angles as they are claiming. They would be better off specifying LED's with a wider viewing angle.....

The Davis light has a fresnel lens which may well be optically better. :rolleyes:
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Just noticed that as well, they seem to have done a lot of homework in everything else and have had a sample running for a few thousand hours so hopefully there is enough spill to cover in the real world and would have noticed such a glaring error.
Be nice to know.
 
GHA said:
Seems like they've looked into this already and it doesn't look like an issue... using these... [Cree LEDs]
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Thanks, at least others shared my thoughts.
With Cree I would expect they would be OK, I was more concerned about someone buying cheap LEDs.

Rigger Mortice said:
Out of curiosity; What kind of price level would you expect if you were buying in hundreds or, say, a thousand?
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If you are thinking of producing this board, please tidy up the layout first :)
 
nigelmercier said:
If you are thinking of producing this board, please tidy up the layout first :)
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I'm not thinking of making it. Just curious.
I knocked my anchor light up a few years ago which is almost exactly what Willam-H described in #10....right down to using a small glass jar (I used one of those little bottles that food colourings come in). I can't remember if I used an Op amp or a 555 timer but, as it switched the LED's on without any other components, it was probably a 555 with a bit of hysteresis thrown in for good measure..

Comes in very handy as an inspection light and a cockpit light, but I have no idea if it conforms to any regulations. It's bright, reliable and cheap. For an anchor light that's all that really matters! :o
 
Rigger Mortice said:
Design flaw number two. :D

Those LED's have a viewing angle of only 15 degrees. With 15 LEDS full 360 degree coverage will be poor. It certainly won't be as bright from all angles as they are claiming. They would be better off specifying LED's with a wider viewing angle.....

The Davis light has a fresnel lens which may well be optically better. :rolleyes:
Click to expand...

Having another look at that, (page 7 on the data sheet) the 15deg is where the luminosity Tails off to 50%, at 24deg there's still a good few percent from each adjacent diode visible so maybe no design flaws so far.

But no obvious supplier of the 5mm cree emitters in UK, what does the panel reckon to something like..
http://uk.rs-online.com/web/p/visible-leds/7133992P/
Or
http://uk.rs-online.com/web/p/visible-leds/7344745/
 
GHA said:
Having another look at that, (page 7 on the data sheet) the 15deg is where the luminosity Tails off to 50%, at 24deg there's still a good few percent from each adjacent diode visible so maybe no design flaws so far.

But no obvious supplier of the 5mm cree emitters in UK, what does the panel reckon to something like..
http://uk.rs-online.com/web/p/visible-leds/7133992P/
Or
http://uk.rs-online.com/web/p/visible-leds/7344745/
Click to expand...

Both of those would do the job but, as they cost more than 50p each (plus VAT & delivery?), not exactly cost effective. It would be cheaper to get a made up bayonet or capsule light which would come complete with regulation. Alternatively get some high intensity LED's for pence off Ebay.

It's only an anchor light.
 
Rigger Mortice said:
Both of those would do the job but, as they cost more than 50p each (plus VAT & delivery?), not exactly cost effective. It would be cheaper to get a made up bayonet or capsule light which would come complete with regulation. Alternatively get some high intensity LED's for pence off Ebay.

It's only an anchor light.
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:)
Exactly!
A main design concern for the bebi was and is for use on a cruising boat, where it's well up the list of "very important things!" needing to work every night for years on end in any weather without fail.
Bayonet would still mean having to construct a shatterproof waterproof housing and cheapo eBay LEDs - why bother just to save a few quid on a such vital piece of boat kit. :)
 
GHA said:

:)
Exactly!
A main design concern for the bebi was and is for use on a cruising boat, where it's well up the list of "very important things!" needing to work every night for years on end in any weather without fail.
Bayonet would still mean having to construct a shatterproof waterproof housing and cheapo eBay LEDs - why bother just to save a few quid on a such vital piece of boat kit. :)
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I think you're slightly overstating your case. Yes, of course an anchor light is important but it hardly needs to be specified as if it is part of a NASA moonlanding mission. :D After all cruisers used old fashioned light bulbs and hurricane lights for decades before the LED came along. Even cheapie LED's are far more reliable than either of those. However, other than the fun of debating this one, I think we've taken it as far as it can go.

By way of constructive comments though.....
FWIW I wouldn't use a bayonet fitting in an anchor light. It's easier, and more reliable, to get a capsule fitting and solder it straight onto the board.
For all the questions about reliability I think the biggest problem is at the other end of the wire. I've always found cigarette lighter plugs to be ridiculously unreliable
 
Rigger Mortice said:
I think you're slightly overstating your case. Yes, of course an anchor light is important but it hardly needs to be specified as if it is part of a NASA moonlanding mission. :D
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Suspect you've never been long term cruising ;)
60p LEDs instead of unbranded eBay **** ain't really over the top now, is it. Especially after the Vf variability discussion.

As for ciggy sockets, I went over to 3 pin Xlrs with a little adaptor cable for the few that haven't been swamped over yet.
Much better. :cool:
 
Rigger Mortice said:
Design flaw number two. :D

Those LED's have a viewing angle of only 15 degrees. With 15 LEDS full 360 degree coverage will be poor. It certainly won't be as bright from all angles as they are claiming. They would be better off specifying LED's with a wider viewing angle.....

The Davis light has a fresnel lens which may well be optically better. :rolleyes:
Click to expand...

From the new makers....

No visible taper in real life... From over 25' individual LEDs cannot be discerned. Under 25' it's too bright to look at comfortably.
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Anyone know who might do a plastic cap like..

120421h.jpg

No luck in homebase :)
 
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GHA said:
Downside of living aboard is not having an address - any of the High street?
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Any plumber's merchant. I know where my local one is, but that's not much use for you.

Homebase is not a useful supplier for real things :)

You might find one in B&Q, but they seem to have drifted towards Homebase's "fancy light fittings, rugs, and extortionately priced screws for people to whom putting up a shelf is a major project" niche in recent years. Their plumbing range might not stretch beyond idiot-proof push-fit any more.

Wickes could be a good bet.

Pete
 
nigelmercier said:
Back to the OP, I'm having second thoughts about this circuit, I don't know why I didn't spot the fundamental flaw the first time. Although the circuit uses a constant current supply, it then splits that current into the four LED strings. The characteristics of LEDs vary, so one of these strings will take more current than the others, causing the LEDs to heat up more than the others. This can lead to thermal runaway.

The effect can be reduced by using good quality LEDs and matching the Vf during construction, but it is still a concern.
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Exactly, the negative temp coefficient of Vf means the warmer leds will draw more power and get warmer still.
 
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