DIY auto turn on anchor light circuit?

[GHA]

For the electronics boffins - any (cheerful and useful ) comments on a circuit to automatically turn on the anchor light please?

Light is also DIY and draws about 0.1A, this is very much just a schematic. There should be a FET or something capable of handling the power knocking about in a box somewhere onboard. Light dependant resistors are these:-
https://pi.gate.ac.uk/pages/airpi-files/PD0001.pdf

Light Resistance at 10Lux (at 25℃) 8～20KΩ OutlineDark Resistance at 0 Lux 1.0MΩ(min)

The resistor & capacitor values here are just what came up as defaults on fritzing.

Will this work? Don't really want to get too complex if it's not necessary.

TIA.

 

[alahol2]

I'm not really electronics savvy...
I've used this circuit several times and the lamps work fine once calibrated using the potentiometer. I'm fairly sure it came from someone on here, sorry I can't credit the original contributor

 

[Arcady]

If you have a standard bayonet fitting, consider one of Boatlamps dawn to dusk LED bulbs: https://boatlamps.co.uk/collections/anchor-lights/products/bay15d-15-smd-5050-dusk-to-dawn-led-replacement-bulb. I doubt you will find a simpler solution.

 

[GHA]

If you have a standard bayonet fitting, consider one of Boatlamps dawn to dusk LED bulbs: https://boatlamps.co.uk/collections...15-smd-5050-dusk-to-dawn-led-replacement-bulb. I doubt you will find a simpler solution.

Ta but doubt you'll find one of those anywhere near an anchorage round here

It's DIY light with wires going into epoxy filled enclosure suspended under the anchor ball so no bayonets to corrode.

 

[GHA]

I'm not really electronics savvy...
I've used this circuit several times and the lamps work fine once calibrated using the potentiometer. I'm fairly sure it came from someone on here, sorry I can't credit the original contributor

Ta, will give that a go on some breadboard - what's the advantage of ganging a couple of transistors? Is that for a narrower on / off light intensity window?

 

[alahol2]

Ta, will give that a go on some breadboard - what's the advantage of ganging a couple of transistors? Is that for a narrower on / off light intensity window?

From what I remember of the original thread it ensures that the light doesn't flicker on/off at dusk. So, yes, effectively what you say.

 

[GHA]

From what I remember of the original thread it ensures that the light doesn't flicker on/off at dusk. So, yes, effectively what you say.

Google is better than my memory! The circuit was in the original thread about the anchor light

http://www.ybw.com/forums/showthread.php?415710-Homemade-LED-anchor-light-circuit

 

[ianj99]

Ta, will give that a go on some breadboard - what's the advantage of ganging a couple of transistors? Is that for a narrower on / off light intensity window?

The pair of transistors make up what is known as a Darlington pair which has much higher gain than a single transistor. This does make for more sensitivity (gain) but doesn't really affect the on/off switching window.
Ideally you need a circuit with hysteresis which means the switch on and switch off light level thresholds are different to stop flickering as it begins to get dark, or there is a bright moon.
Alternatively, a 5minute switch off delay could be used.

 

[GHA]

The pair of transistors make up what is known as a Darlington pair which has much higher gain than a single transistor. This does make for more sensitivity (gain) but doesn't really affect the on/off switching window.
Ideally you need a circuit with hysteresis which means the switch on and switch off light level thresholds are different to stop flickering as it begins to get dark, or there is a bright moon.
Alternatively, a 5minute switch off delay could be used.

Would one transistor be OK then? Think there are some ttl fets somewhere, and would the capacitor help much to smooth out the hysteresis?

Ta.

 

[st599]

http://www.ti.com/lit/ug/tidu020a/tidu020a.pdf

Without Hysteresis it will flicker.

 

[ianj99]

Would one transistor be OK then? Think there are some ttl fets somewhere, and would the capacitor help much to smooth out the hysteresis?
Ta.

You can use a logic level mosfet such as a STP40NF10L instead and also connect a large capacitor across the ldr.

The fet will start to turn on at about 3v. You'll need to experiment with the capacitor - start with say 1000uf as the time constant will depend mainly on the ldr resistance.

 

[alahol2]

http://www.ti.com/lit/ug/tidu020a/tidu020a.pdf

Without Hysteresis it will flicker.

Maybe, theoretically, it should flicker. In practise, over maybe 15 or more years of use, I've never once seen it flicker. It switches on slightly dim but very soon reaches full brightness (less than a minute). I must admit it may flicker in the morning, when switching off, but I've never been awake to see it.

 

[GHA]

You can use a logic level mosfet such as a STP40NF10L instead and also connect a large capacitor across the ldr.

The fet will start to turn on at about 3v. You'll need to experiment with the capacitor - start with say 1000uf as the time constant will depend mainly on the ldr resistance.

Well, having a fiddle with whatever bits came to hand this seems to work OK.

One of these as a FET..
http://pdf1.alldatasheet.com/datasheet-pdf/view/17184/PHILIPS/BUK553-100A.html

No flicker to my eye anyway, output LED grows lighter/dimmer as you pass your hand over the LDR, full on before the LDR is completely covered.

So looks like we're in business barring some more tweaking and experimenting. Yay!

Might have to wait til the anchorage ain't so blimmin rolly before getting too involved with a soldering iron and little components though!

Thanks guys!!!!!!

 

[GHA]

So who's good at perfboard. Mine always ends up looking like a mess

 

[GHA]

Well, seems to work OK with just a little LED to test but won't win any prizes for tidiest board ever, front's better than the back

So now just needs glue gunned into a little enclosure and velcroed out of the way somewhere with the LDR stuck inside a port light .

And hopefully the days of nipping ashore for a quick shop then feeling uneasy hours later after dark in a bar somewhere cos the anchor light is off are behind

 

[ex-Gladys]

...or buy a boat specific light activated LED bulb for about a fiver more than an ordinary one...

 

[GHA]

...or buy a boat specific light activated LED bulb for about a fiver more than an ordinary one...

Why downgrade when there's a very good bright waterproof diy anchor light already working every night?

This cost nothing from bits stashed on the boat already.

"[h=1]Forum: Practical Boat Owner's Reader to Reader[/h]Share practical, hands-on information.
"
Or....
Don't bother, just go spend money on something not as good....

 

[GHA]

Fitted and working, with a little LED added to the enclosure to see when it's putting out power (with a 2.2k resistor so it's quite dim )

So, final question - what potting compound to put on the board in the enclosure. Read somewhere cheap silicon isn't a good idea as it's acidic and might cause corrosion. What about some glue from a glue gun?
Bearing in mind "unobtainium 2987" or such like may be the best known to mankind but getting anything remotely exotic round here might be a tad challenging.


And now the temptation to hole up in a little bar somewhere til after dark so the row home will be towards a triumphant brightly shining anchor light is almost overwhelming