Connected Shed

Having used small LED solar lighting in our garden, we were dissappointed with the performance of the lights. Not only do they not last very long but, they are also not very bright. Each device also requires an unsightly solar panel (albeit a small one) and there was no control over when the light went off. On days with little sun, they would often come on for very short periods of time. Our plan is to add a low voltage wiring to each garden light and to provide more intelligent control over the lighting. In addition we plan to provide a single, large battery power source that is charged all year round by PV solar panels.

Having reviewed the Fibaro Universal Z-wave Sensor, we saw an obvious opportunity to add one to this project. We will use the sensor to monitor a micro-switch on the shed door, to connect an additonal twilight sensor for controlling the external and to monitor the temperature inside the shed, outside the shed and also the ground temperature. These will all be connected using the wireless Z-Wave.

We have also run an Internet connection down the wall cavity and into the shed but, we haven't found a need to use it yet.

To reduce the amount of power used, all of the lights use LEDs and the majority are warm white LEDs. Because of the voltage drops, each light uses a constant current driver to optimise light output.

Implementation

Shed under construction
Our starting point for this project was a spare 12V car battery. This is has a large capacity and can be charged via some solar cells, without requiring a charge controller. The key is to keep the battery from being frozen and to put more power into it through the course of a day, than is taken out. The former is achieved by having built a shed that is against the side of our current house. This means that it is effectively heated slightly through the wall of the house. The shed is also reasonably well insulated with a clear 25mm triple-wall polycarbonate roof. This also lets sunlight through to heat up the shed.

12V solar panel
Solar power is initially provided using two 4.8W 12V solar panels. These were bought from Maplin (part no. N30CX) whilst they were on sale. We may add more power generating capacity as the load from the garden lights increases.

Lighting Control

12V timer
To provide independence from our wider home automation system, we have used a seperate 12V timer module that restricts the hours that the external lighting comes on. These are available on eBay and very cheap. We might replace this with a Z-Wave controlled switch later.

In parallel with the timer, we also have a light-level sensor, which ensures the lights only operate when it is dark outside. This saves a lot of battery power in the summer months, where a timer alone would switch on the lights

Manual Lighting

The 12V battery power is also distributed to patio areas (via a fuse) to waterproof sockets for 12V lighting at tables, etc. These are manually controlled.

Temperature Sensors

The first temperature sensor will be inside the shed, close to the battery. The second will be on the outside of the shed and mounted in a waterproof enclosure. The third will be sealed in a waterproof tube and buried in the ground at a depth of 15cm.

Summary

The car battery and solar cells used have survived a whole year of usage so far, without any charge controller or other forms of battery management. It would be good to add some means to remotely monitor the battery voltage in the future though. We would like to add a larger solar panel in the near future, with higher power output (e.g. 40W).

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