I would like to put a few small lights along my main gate, to reduce the chances of someone crashing into it. The gate slides, so the electricity will have to come from solar panels, or long-lasting batteries. Ten or twelve lights would be enough. The gate is about 22 ft wide. Unfortunately the location gets very little direct sunlight in winter. However the solar panel can be any reasonable size without looking too odd. I'm envisaging 300 x 300.
A 50W panel would be approx 500x700mm, between november and february, would give you a grand total of 8 kWh, so 66 Wh/day, if you want 12 LEDs to run 16 hours a day, they need to be about 300mW each (and that's disregarding battery losses)
Can't you rig some sort of power supply that makes contact when the gate is closed?
Or put the light source on the post, and use fibre optic bundles as a light pipe on the gate?
You could also be a bit more frugal with the power by flashing the warning lights, rather than having them always on.
Would reflective tape not be simpler?
You can run a flexible cable on a cable drag chain onto a sliding gate (you'll often see similar in car-washes).
I used a carbon fibre fishing rod wit a steel wire attached to it and the back of the gate with a twisted pair of wires to carry the current.
the rod placed halfway along the track the gate retracted to at the yard where I worked 15 years ago.
I've thought about it, but the gate positioning is not all that accurate. I think it would be a maintenance issue. Unless anyone had any good ideas. Bill
I'd rather not have them flashing. Bill
The panel would have to be vertical to pass between the posts that support the gate. Six lights would be enough. It's a very dark area, so I think 300mW LEDs might be bright enough. Can you point me to some examples of these? How do I make it so the lights come on at dusk and go out at dawn? What do I do about voltage regulation? Bill
Far too complicated, get some from Audi/Liddle with rechargable cells and solar powered. Quite cheap. Had some for years and still running now the wife has passed.
A CdS cell detects dawn.
You've probably seen these sensors at some point in your life.
There are photodiodes and phototransistors, which react quicker to light sources. All sensors have dark current as a source of noise.
*******Reliable batteries, that work in the coldest weather, are expensive.
The engineering is toughest in winter. That's what all this expensive excess is about. If the project only had to work in summer, the project becomes a lot cheaper.
The fairy lights here, have never worked that well in winter. Usually they're flat in mid-winter and not lighting up. And in summer, they might run until midnight. That's just to give a comparison to an "unreliable" solution. Most of the time, your gate would be unlit with those. They just drain too fast, and cold weather affects the Lithium iron Phosphate batteries.
*******Reflective tapes are another item you can use on a gate. Works with automotive headlights. You cannot use just any product for this, as people will take your money and give you a poor quality (low reflection) tape.
Paul
You are not trying to light up the area in front of the gate but to make people aware that there is a possible obstruction in front of them. I have a couple of discrete LEDs working from 4 off AAA batteries and they are constantly on for months until the batteries die. I'm running these LEDS at around 0.2mA (approx 0.5mW) and they easily can be seen from greater than 5m. With a different supply arrangement (series resistor) they could be run at 30mA (approx 100mW) and burn out my retina :)
As others have suggested, also use some reflective tape which will be illuminated by car headlights
Big Clive solar dusk to dawn switching
Random example of discrete LEDs (data - scroll down)
It's now possible to buy sodium ion batteries from China: they are much cheaper per Wh than lithium cells and supposedly work down to -30C, with the downside that the voltage curve is less flat (4V down to 2V usable range). Cycle life is better than lithium ion but slightly worse than LFP.
Theo
So flash them at 100Hz :-) They will look like they are on, but consume less power (at expense of apparent brightness). It is common technique with LED lighting to lower average power consumption.
PV panels with no direct sun will give very little, you'd need to massively oversize them. LEDs require current regulation or limiting rather than voltage. Ultrabrights would work.
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