Greenhouses are used for growing plants. Plant rely on an amount of sunlight to grow, and so we can also use some of this sunlight to power the control system. Harvesting sunlight to product electricity is possible by using solar panels.
The Kitronik Smart Greenhouse kit includes a 5697 Environmental Control Board is designed to provide both environmental sensor inputs to, and control outputs from a BBC micro:bit.

Adding a Solar Panel to the Kitronik Smart Greenhouse:

The board is powered by electricity, and can be powered by a mains adapter, or by batteries. Batteries are ideal if there is no connection to mains electricity available, but they are limited in capacity.
The design includes a solar panel input, which can be used in conjunction with rechargeable batteries to produce a solar powered control board. It has a reverse blocking diode on board – to prevent the discharge of the batteries when the panel is not sufficiently illuminated to charge them. For more information on Solar power see this guide.
The solar add on kit (56113) consists of a Solar Cell and 3 NiMH rechargeable batteries.

The solar panel (3608) is capable of outputting up to 130mA. It is generally accepted that NiMH rechargeable batteries can be left on charge indefinitely at a rate of 1/10 of the capacity of the battery. The batteries (2278) are 1300mAH – which is a good match for this 1/10C charge rate.

How to assemble the Solar add on kit:

Firstly, insert the 3 NiMH AA batteries into the battery cage on the reverse of the Environmental Control board.

Then connect up the Solar Panel. The Solar panel comes with 2 leads – Red and Black in colour. The Red lead connects to the Solar Panel Input terminal marked +

Tighten the screw terminal, and connect the Black lead to the terminal marked -, also tightening its terminal.

The Kit is now assembled, and ready to power your environmental control board. You can confirm this by switching the Environmental control board on – its Power LED should light up.

A simple stand can be created to hold the solar panel. This DXF contains a simple stand designed to be laser cut from 3mm thick material, such as acrylic or ply.