# 1B. Principles and Practices¶

## Description¶

In winter there is no sun in our garden. Once in a while the sun is reflected into the garden by a neighbors window. This lasts just for a couple of minutes but I always enjoy this moments of sun. This made me think - what if I put a mirror on my neighbors roof which adjusts to the sun’s position so that it reflects sun into my garden all day long?

Once I searched the internet I discovered that I’m not the first one to come up with this idea and that such a mirror that adjusts to the sun is called a heliostat.

Heliostat definition from merriam-webster.com

An instrument consisting of a mirror mounted on an axis moved by clockwork by which a sunbeam is steadily reflected in one direction

As a final project I want to build a heliostat to reflect sun from the neighbors roof into our garden.

## Control mirror angle¶

How do I know how the mirror should be positioned to reflect the sun to the right place? These are some options I can think of:

• Calculate sun’s position, know target position, calculate mirror angles
• Sensor at destination (where sun should be reflected)
• Sensor between heliostat and target

## Mirror movement mechanics¶

The horizontal and vertical angle of the mirror have to be adjustable. There are many possible mechanical designs to have this freedom of movement. I took a look at some existing designs for inspiration.

## Open questions¶

• Necessary range of movement?
• When the mirror reflects the sun to a place which is far away (e.g. 100m) a small change in mirror angle leads to a big movement of the spot of reflected sun. How accurate does the mirror positioning have to be to provide an acceptable positioning of the reflected spot?
• How fast does the mirror’s reflective property degrade when it gets dirty?
• Can I make it solar powered? That would make it easier to put on a roof
• It would be really handy to be able to adjust the target location remotely (without having to go on the roof). How can this be achieved?