Arduino heliostat calculates the position of the sun

We’re past the winter solstice and the days are getting longer, but that doesn’t mean we’re not sick of the sun setting around 5 in the afternoon. There is a way to get more sunlight through our windows – a heliostat. Lucky for us, [Gabriel] sent in his Open Source Sun Tracking / Heliostat project that can reflect sunlight through our windows all winter long.

Using mirrors to brighten up a room is an ancient practice; a few thousand years ago, heliostats went by the archaic term, “slaves.” Luckily there’s a far more elegant way of doing things nowadays – an Arduino. [Gabriel] came up with an Arduino sketch that calculates the altitude and azimuth of the sun using only latitude, longitude and time zone. [Gabriel] used this sketch to drive a pair of stepper motors and reflect sunlight through his window.

You can check out [Gabriel]‘s demo of his heliostat after the break.

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Building a solar power heliostat

[Frits] has been working on an solar panel heliostat (in Dutch, check out the translated page here).

The heliostat uses a small PICAXE to control the motor, along with an DS1307 real-time clock to make sure the motors start at dawn. Instead of using optical encoders or magnetic sensors, the angle of the heliostat is measure with a pot attached to the drive shaft. [Frits] did a lot of data collection to figure out that this method is accurate to about 1 degree – just fine for something that doesn’t need to be exact.

According to [Frits] this heliostat will put out 12 to 50 percent more electricity than a fixed panel. Although the build does seem a little bulky, putting it on a  house with a roof pitch of 23.5° would greatly reduce the horizontal profile.

A video of a solar panel rotating at 15 degrees/hour isn’t that interesting, so [Frits] posted a clip of 6 mirrors slewing around fairly fast to demonstrate his system. Check it out after the break.

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