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Joined: Wed Nov 27, 2013 1:23 pm

2 axis Heliostat / Sunfollower

Wed Nov 27, 2013 2:05 pm

Hi all,

as I have a bunch of ideas but no hints how to realize them, I am asking you folks.
More brains are more effective ... ;)

Something about me, 15 years in Experience with webprogramming (php, JS, etc ..) and experience with Linux, mostly Ubuntu.
I fairly cope with the raspberrypi. Everything is running apache webserver, php, mysql.

Anyway, I want to realize a 2 axis heliostat with my raspberrypi.
The diameters of the "table" will be 1mx1m. The table is grasped by an aluminium profile,
which is mounted with a 2 axis joint on a steel tube with 15cm diameter.
So that should be solid enough.

I have read much about the concepts, (sundata, versus following the lighter areas).
I am prefering the "following the light" method.

But I don't get all these things connected.

I want to write a program in php (preferred), which will steer the electro engines.
* But what kind of engines should I prefer ?
* Normal ones with gear mechanism (Lets say 1: 3500) so that the steps will be most precise, or stepper engines (expensive with drivers ...)

And how do I get these things connected to the PI?

I would like to have 4 LED (no LDRs please) top bottom, right, left which send different in the middle.
According to the Voltage and a certain barreer, the two axis should be steered, so that the heliostat will always show into the lightest area.

From the horizontal way of move, it can move 360°
From the vertical way about 270°.

Do you know how bad this is, to have so many ideas in the head, but no idea where to start?

So maybe someon could point me in some useful direction.

Thank you all for reading.


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Joined: Fri Dec 25, 2015 5:35 pm

Re: 2 axis Heliostat / Sunfollower

Fri Dec 25, 2015 5:48 pm

I've been considering this problem for some time I think there is a simpler solution. There is already an astronomical table of sun rise, tracking and setting for every location on the planet. It's a question of sinking the movement of the heliostats or solar panels to the known data. Just a stream of mathematical calculations required, the more frequent the calculations the more accurate the tracking.
So that on a day when sun is in and out of clouds it's always in the optimum position.
The pi can then also be given the secondary task of positioning the array to minimise wind damage etc.

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Re: 2 axis Heliostat / Sunfollower

Sat Dec 26, 2015 2:34 pm

Lemme make sure I got this correct -you want a 1Mx1M flat surface to always face the sun - not necessarily to have it track the sun and reflect the light to a another stationary target? I've done the latter.

My first advice would be to use regular gearmotors - just because it's simpler. The sun moves slowly enough that with the right gearing you can "bump" the array and it won't over travel. I might try a cordless screwdriver for a motor with some additional gearing for a cheap motor.

Even before you get that far - install the wiring pi library and read up on that on the wiringpi website - master reading inputs and using that data to manipulate outputs to LEDS. Once that is done it's an easy matter to swap LEDs for relays.

Tony is correct about the tables and timing, and that would require either a stepper or some kind of feedback for positioning. I guess it also depends on how precise you want to go - Keep in mind I just wanted to focus the sunlight from several 1mx2m mirrors onto a single .25mx.25 target to heat a tank of water across the yard - I tried a few ways (trying to find the most economical/fastest way to build dozens of these things) and what ended up being the cheapest/fastest to produce was actually to not even use a microcontroller but rather to make the circuit relatively "dumb." I had photo transistors feeding at the array and around the target and using windshield wiper motors, I let one axis go back and forth (when sensor said there was enough light to bother) until it lined up, the other axis was enable to do the same. The phototransistors at the array fed relays which took signal the 12 meters or so back to the array where the controller was. I wish I had photos or a schematic or something...been a long time

Of course this was before I had a pi and was using basic stamps and picax micros. I might use the pi now...I'll ponder this a little on my drive and chime back in later.
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Joined: Mon Sep 19, 2016 11:32 pm

Re: 2 axis Heliostat / Sunfollower

Mon Sep 19, 2016 11:40 pm

Hi Triplehelix,
Have you managed to finish your heliostat project with the Pi?
I've got a heliostat on a 7 meter pole at my house in S-Africa, but I am very interested in the Pi version of it. My heliostat track the sun by means of an algorithm. I also have a gps interface for time and position, as well as an anemometer for when the wind picks up.

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Re: 2 axis Heliostat / Sunfollower

Tue Sep 20, 2016 9:58 am

Don't hold your breath waiting for a reply. Triplehelix hasn't been near the forum since November 2013 (yes, that's nearly three years ago).
Languages using left-hand whitespace for syntax are ridiculous

DMs sent on or LinkedIn will be answered next month.
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