Garden lighting is provided for safety, decoration or convenience.
Solar Garden Lighting
Cheap, solar garden lights are readily available but they vary in their light output and quality. They typically incorporate a small solar PV panel, that charges an in-built battery during the day and then uses this to light up some LEDs when the light level drops. The internal circuit is quite simple and lights up the LEDs until the battery discharges to a certain level.
The problem with these lights is that they have a very small solar panel and a small AA size battery (or a pair of them). This means they don't store much energy and thus don't give out much light and for a short period of time.
In our current garden, we use a single central power source. The main disadvantage of this is the additional wiring required but, the benefit of decent lighting that works for long periods of time is worth it in our view. To achieve this we use some decent sized solar panels (rated at ~12W) to trickle charge a large 12V battery (we used an old car battery). The other advantage of this is also better control of when the light is on/off. We have a twilight sensor to determine when to switch the lighting on and our Home Control System (HCS) can also control when it goes off.
We use fuses from the garden lighting battery bank.
In order to make power distribution easier and extensible, we have run our cables between a number of water-tight underground enclosures. Typically, there is one of these near each garden light. These are fabricated by using standard 110mm soil pipe parts, to reduce the cost of installation. Each one costs less than £15 in parts.
A length of 110mm soil pipe is cemented into the ground with all the cables coming up through the bottom. The pipe is set in wet cement to ensure a good seal inside and out. Once the cement is dry the bottom is then fully sealed with a resin poured inside the pipe. A single socket is then fixed to the top of the pipe (Floplast 110mm Single Socket) and we have used solvent cement at all joints.
To ensure a solid fixing and to ensure it won't rotate, a stainless-steel bar is inserted through 2 holes drilled in the sides of the pipe, before it is cemented into the ground.
By keeping the pipe sticking up out of the cement, it is possible to add other cables later. These can be drilled though the soil pipe sides and fully sealed. The wires are all kept long enough to work on outside of the screw cap.
The top is sealed with a screw top cap (Floplast 110mm Screw Cap). Ours have been mounted so that the screw caps are just below the soil surface. You could put them in locations with flower pots or planters on top, to hide them.
A centralised 12V power supply can only be used with lighting designed to accept a 12V power supply, which is a bit limiting. Most decorative garden lighting is not designed to do this. To get around this problem we use a voltage regulator to provide the required lower voltage to power various lights.
These Tesco berry lights have a separate solar cell and power module and two AA batteries providing about 3V dc. Our testing showed that we get the required brightness using an LM317 adjustable output voltage regulator set at 2.8V. At this voltage two sets (50 LEDs per set) of lights draw about 110mA. When using a 12V supply the LM317 is dissipating quite a lot of power so a heatsink is required. The actual voltage at supplied at the regulator is much less than 12V though, due to the voltage drop over the wiring around our garden.
Close to these lights, we have a small waterproof (IP56 rated) box with a two-way switch (on - off - automatic) and the voltage regulator inside. There are three wires going into the box: OV/Ground (black), +12V permanent feed (red), switched/automatic +12V (orange).
These lights are wrapped around some decorative rope, with the wires following the rope spiral, to make them difficult to spot. The come on automatically when it gets dark and go off again at 11:30pm. They are powered by a battery, which is charged by solar panels.
Any mains power distributed underground needs to use armour-plated cable. This is relatively expensive but avoids issues with voltage drops over longer distances.
Low voltage wiring can be used using ducted wiring and this can be done using cheap plastic conduit or even hose pipe. It is much safer than using mains voltages but, the voltage will drop off with distance. One way to negate the effect of these is to use lighting that works at a lower voltage to the supply and to have local voltage or current regulators near each light.
Around the garden we are using automotive 1.0mm2 32/0.2 cable rated at 16.5 amps. It comes in 100m rolls and is relatively cheap. It also has a low resistance. We have also used this in our home for home automation.
As described above, we are using three cables:
- black = ground
- red = permanent +12V dc
- orange = timer switched +12V dc
We initially used a 12V dc timer switch (bought on eBay) to control our garden lights but, this doesn't take account of the changing length of days or summer time changes.
We are now using a more intelligent control system where our Home Control System (HCS) turns on the lights shortly after dusk is detected and then switches them off later, depending on the day of the week.
- Let cement dry properly before you put lids on enclosures. It has a lot of moisture content.
- Tin all leads with solder and solder all connections where you can. It is much less likely to corrode.