Heliostat - What's a heliostat?

I want to start building a heliostat, with the eventual goal of making a solar tracker, but for now, I really want to just build something that will send light through my window.

Why? You may well ask.

And "What's a heliostat?" you may add.

A heliostat is the kind of thing someone with a water drop lensed microscope might have used to get some light on the subject*. Early models involved humans, who were forced to point shiny things in such a way as to reflect the light to shiny men's laboratories. Later versions incorporate wind up mechanisms. For a single day device, all that's required is that it turns 15 degrees every hour, as long as you are willing to manually adjust the elevation for the particular day you are using the device,
a heliostat will track the sun so that a mirror will always reflect to the place I want the light.

The solar tracker is like a heliostat, except that the place it's pointing at is always moving. (that point being directly at the sun wherever it is. But the solar tracker is for another day. Actually all of this is for a great many days.

For now, I'll be working on a small digital device that controls the direction a small mirror is pointing, to make it always reflect light to a fixed point. Basically a way to bring some natural light through a window that doesn't see a lot of light.

There seems to be a few different ways to create some linear movement. Linear movement being required to lift a side of the mirror to adjust the direction of the reflection in the up and down aspect.. I figure if I can raise or lower one side, and make the entire device pivot around a mast, I should have all the degrees of movement required.

According to the invention engine, one way to create the required angle might be to glue a hinge to a mirror, and mount that to a mast to support it. Tie a string to one side of the mirror, then wrap it around a tiny winch mounted half way up the mast, then tie the other end to the other side of the mirror. That would give me up and down, and then all I need is a way to rotate the entire device, perhaps using a geared motor, and a pulley.

I haven't really tackled this bit of the design, but the control of the motors could be done via a PICAXE chip similar to that used in my demand feeder. and some light dependant resistors (LDRs).

If two LDRs were arranged so that when the device was pointing correctly, they were both in full light, but when one became shaded, the motor could be turned in the correct direction to make the adjustment.

A similar arrangement could be made for both the up and down, and rotational movements.

I'm off to an electronics store to buy some stuff.

*may not reflect reality.

120 Things in 20 years is busy finding bits of heliostat. 

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