Build a mini solar tracker

[Grelinette]

Hello,

Yesterday afternoon I had a little time to lose and I tinkered this little solar tracker. For the moment it is in test phase to see if the ratio of the 2 pulleys is precise enough so that the plateau makes 1 turn in 24 hours.

So I used a small recycled 20 € watering timer, which works with 2 AA batteries from 1,5v.
On the small spherical valve that rotates on an axis, and accessible by delicately cutting the plastic case with a hacksaw, I fixed a small 2,4 pulley cm in diameter, a circumference of 7,5 cm.
The large tray has a diameter of 28,8 cm (12x2,4cm), so it is 1turn when the small pulley makes 12.

For programming, I put 1 valve opening every hour for 30 mn, so that the small pulley fixed on the valve rotates a quarter of a turn every 30 mn, 12 turns in 24 hours; the board will make 1 turn in 24 hours.

For the drive belt, I used a brown rubber cord that is used in gardening to attach the plants to a stake: it is a small elastic tube that sticks easily with a glue for soft plastic (kind glue to patch). I hesitated to add a tension wheel but for now a belt works well and does not slip.

The tray is fixed on a ball bearing recovered in a car-breaker

The groove that holds the belt was dug with a grinder whose disc just brushed the edge of the plate by rotating it on its axis

You can put what you want on the board: small solar panels, flower pot or even the cat's basket so that its exposure to the sun is optimized!

I started it last night and I will see if the gear ratio is accurate enough to follow the sun to compensate for 30 mn.
Depending on the deviation (rotation too fast, so the diameter of the plate too small, or the opposite, too slow rotation) I dig a little more the throat of the tray or I add an elastic in the throat to increase slightly the diameter.

[pierredecamargue]

Hi Grelinette,

I just read your subject.
I am thinking of building a system with a mirror that would follow the sun's course to reflect it in my house in order to heat it (it is not exposed to the sun).
Does the system you are proposing here seem to be the best compared to those using photovoltaic sensors?
In another subject, you proposed a workshop for children, in what area are you?

Good continuation.

Pierre

[chatelot16]

the idea is interresting

if the swivel mirror is placed anywhere, the movement to give it is quite complicated, more complicated than a single rotation on an axis

cells that measure the position of the sun are not the simple solution, since the mirror should not target the sun, but put itself in the position that sends the sun to the right place

the sun detector can be mounted in the middle of the window and see if it sees the sun in the middle of the mirror ... when the sun is no longer in the middle of the mirror must correct the position ... but problem if the sun is hiding, and when it comes back it is no longer in the mirror the system does not know anymore or look for it

I do not like the solar tracking system with cell because it takes motor fast enough to find the sun after a period without sun ... I prefer a follow-up of the sun by following a theoretical program that the sun is visible or not

an optical tracking can be a means of autoreglage an inteligent follower: the day when there is sunlight it is seeing the position of the sun in the mirror and records to be able to follow theoretically when there is no sun

another solution: choose the location of the mirror so that a simple rotation on a single axis is sufficient: the light ray must enter through the window along the axis of rotation of the earth: the mirror must return the sun of 90 ° at the equinox, and a slightly different angle at different season ... this angle varies slowly with a manual adjustment once all the 15 days are enough

thanks to the special position of this mirror a rotation along a single axis 1 tower / 24h is enough: it follows the sun even at night and finds the sun in the morning

as there is no electric cable on the mirror, it is useless to stop the movement in the evening and come back in reverse ... just let it run

[izentrop]

Hello,
Valiant heart, nothing impossible.
To return the same amount of heat as that received to the south, a mirror area greater than that of the southern sunny surface, plus reflection losses, is required. and incidence.
The control logic can be executed by an arduino, an "ephemeris" library and a calculation program.

[Grelinette]

Hi Grelinette,

I just read your subject.
I am thinking of building a system with a mirror that would follow the sun's course to reflect it in my house in order to heat it (it is not exposed to the sun).
Does the system you are proposing here seem to be the best compared to those using photovoltaic sensors?
In another subject, you proposed a workshop for children, in what area are you?

Good continuation.

Pierre

Hello Pierre,
my mechanical system works pretty well, I'm happy with the result, but it's limited to small, light items.
I tested it over several days and the orientation to the sun is correct. There is just a small gap that is increasing little by little because of the lack of precision of my pulleys that are tinkered. It is probably the guide groove of the belt in the big wooden pulley which is too hollow (I made it to the grinder on the rotating wheel) and which has too much reduced its diameter, but it is played to a sixth : I made a reference and I see that after 24h it does not fall exactly in front of the starting point. I think that by changing the diameter of one or other of the pulleys a bit, I can empirically reduce this offset. That said, the DIY was very fast, simple and easy to do, and rather fun with children.

To return to your project, a system with pulleys, belt and irrigation programmer should work with a mirror provided that the mirror support is solid. For example, a car wheel bearing recovered in a car-breaker may be suitable.
I have several models for wind turbines, like this one:

Axle Bearing car.jpg (15.51 KIO) Viewed 11961 times

There is however a reflection and a prior calculation (as written Chatelot) because mechanically follow the sun with a turntable is one thing (finally simple ... with the help of econologists thank you to them!), but returning the sun's rays from the sun moving from a rotating mirror to a fixed point (your house) is surely another problem ... which is also interesting!

Otherwise, it seems that we are almost geographically "neighbors": you are in the Camargue and I am between Aix en Provence (BdR) and Pertuis (Vaucluse), roughly less than 100 km separate us!

[chatelot16]

there is no hope of making a perfect precision with a belt ... even if the diameters are perfect the elasticity of the belt makes a mistake

which is the advantage of a solution with alternating movement, at the place during the day and at the back at night: it allows each end of the night to return to settle on a switch end switch, thanks to a delay day night voluntarily settled with a return time the night a little longer than the time in advance the days

for a photovoltaic orientation that does not require great precision, this system of return to the reference position allows to contain a speed without great precision ... a DC motor supplied with constant voltage is sufficient

for a heliostat that sends the light into a window, even with a return to the reference position each end of the night it takes a motor with good speed accuracy, so the synchronous motor programmer is a good solution ... we take advantage the remarkable precision in frequency of 50Hz

[chatelot16]

To return the same amount of heat as that received to the south, a mirror area greater than that of the southern sunny surface, plus reflection losses, is required. and incidence.

this reflection is interesting! in the case of an old traditional house all the surface of wall which receives the sun heats a little the house ... so even without heating the temperature of the house will be a little habitable except cold


in a well insulated modern house the power of the sun on the wall is useless at all ... so much better if you have a heater but without heating a well insulated house is worse

[Grelinette]

I have not thought about it yet and I admit that I have no idea yet, but how do you imagine the principle of mounting with a rotating mirror, even small, which follows the sun and returns its radius to a fixed point ????

Not simple as a question?

[chatelot16]

it is simple in a particular case: the straight line between the mirror and the window is parallel to the axis of rotation of the earth, and in this case a simple rotation of the mirror at a constant speed is sufficient

if the line between the mirror and the window is not the axis of rotation of the earth, it jumps a system to 2 axis a little more complicated

[izentrop]

There are lots of amateur projects on instructable http://www.instructables.com/howto/heliostat/
and even more on the tube https://www.youtube.com/results?search_ ... y+heliosat