Ian from Thermoguard Instruments replied:

I doubt it will be cost-effective for a couple of portable panels. The ones I've heard of are complex feedback controllers with some sort of detector to tell when it's pointed directly at the sun.

If you are right into electronics I'd suggest a PIC-based open-loop positioner. This could be programmed with a 'map' of suitable position changes each, say, 15 minutes and use a small stepper motor to move the panel frame via a suitable gear reduction. This would give about 25 positions over six hours of exposure.

If this is too complex, then just aim it North at your latitude angle +/- 10 degrees for winter/summer and, optionally, change the East/West tilt manually a couple of times a day.

Ian

Member - Davoe (Nullagine) replied:

I wouldnt have a clue but I would be thinking along the lines of the system and motors/gearing whatever they use to keep telescopes fixed on a planet. high end ametur units have them

traveller2 replied:

In a previous life I worked for Telstra and from memory they decided it was cheaper and easier to fit an additional panel to make up the shortfall than all the tracking stuff.

Kevin1243 replied:

An equatorial telescope mount with a motor drive would work OK, as long as the panel weight is not too much. I have bought from Andrews Communications in the past and have always been happy. A heavy duty EQ5 mount with a motor drive will set you back about $600. The only drawback might be the weight of the mount and counterweights.

Kevin

Member - Alastair D (NSW) replied:

I think it easy to get carried away here.

If you are using solar panels that are not highly sensitive to direction then all you need is a simple motor drive that will rotate the panels by about the right amount per hour. You set the panels at the best starting point and then turn on the system. There is no need to have a highly accurate tracking systems.

A simple stepper motor of the type available from Oatley will be inexpensive, low power consumption and they have a simple driver for it. A 555 timer can be simply used to give the right pulse rate. I think to use programable devices etc is overkill.

Just my thoughts as I have often overdone things myself and then afterwards realised how much time and $ I have consumed unnecessarily.

alastair

Pomgonewalkabout replied:

You may get some ideas from these links as this was something that I was thinking about a while ago.

www.solazone.com.au/tracker.htm

A simple timer circuit operating a relay driving a motor would do the job.

The relay would be on for a few seconds at a time maybe 15 times a day.

More complex circuits could involve heat or brightness seeking circuits but as somone has already suggested, we know where the sun rises and sets so a simple timer would suffice.

By using a relay you wouldn't even need a stepper motor but a normal DC one, the relay supplying voltage to the motor, whilst the panel moves.

Of course if all this gets too expensive then I would buy an extra solar panel.

Ianw replied:

Actually its quite simple to build a sun tracker. Full details were published in one of the electronics mags a few years ago (about 1990 I guess) . It will increase your output by at least 25% per day, as soon as the sun pokes up it will be charging until the sun passes below the horizon in the evening. At the time I bought a panel and did a lot of experimenting and concluded that it was worthwhile doing. The circuit used two LDRs with a shade between them and when the shade covered one LDR a motor moved the panels until both LDRs were in full sun again. Very simple. At dark, the panels were moved back to the start ready for the next morning. Motor used was a rotisserie drive from a BBQ. 3V geared motor operated from 12v for short periods required was no problem and had plenty of torque.
Ian

techo2oz replied:

Hi there,
been there done that and works out that for the extra bulk of the framework etc for the little extra that is gained was not worth it. I now have that extra little space for important things that I take. Unless you are planning on staying in the one place for more than a couple of weeks at a time I would advise simply moving them by hand at least 2 times a day. ( I move mine 3)

Whole setup including the frame and tracker was a few hundred dollars by making it all myself. The frame needs to be sturdy but adjustable to allow for azimuth adjustment but needs to be securely pegged to the ground for those sudden gusts of wind. My setup had 2 X 68 Watt Sola panels mounted side by side but connected via a swing arm. (Wish I had taken photos before breaking it all up again) The swing arm had a pivot lever which attached to a worm drive (length of booker rod) This was attached to a low current low volt motor.

The tracker is a simple device with discreet components that uses shadows to track the sun. 2 LDR's look for the light, when one falls in shadow, it applies power to the motor to move the panels (Tracker mounted on one of the frames of the panels) so both LDR are in the light. A third LDR detects dusk and drives the whole assembly east ready for the next morning. Add a few limit switches and support components and it's it is quite simple yet elegant.

I gave the board away but if I dig around I may still have the drawing here somewhere.

Cheers
Peter

Im.away replied:

Thankyou all for the suggestions so far. I've certainly got a few options now. I'll be sure to post the end result. I've got 4.5 months to make it happen, so It'll end up being a last minute thing of course!

Pomgonewalkabout replied:

I'd be interested in a photocopy / scan of the Silicon chip project if possible?

I have yet to buy a Solar panel and was looking getting a Suntech freedom folding 80 watt type that come complete with a tilting stand regulator and bag or just a 85watt panel on it's own that are about $200 cheaper.

cheers