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[Reply #15 on:]

Threaded rod (aka allthread) is just a very long bolt, if you put a nut on it and turn the rod the nut moves linearly along the rod.

So by mounting the nut to the thing that needs moving and turning the rod the "thing" moves.

So it's just a matter of mounting things in the right place.

It may help if you tell us what needs to be moved.

______
Rob

[Reply #16 on:]

Threaded rod (aka allthread) is just a very long bolt, if you put a nut on it and turn the rod the nut moves linearly along the rod.

So by mounting the nut to the thing that needs moving and turning the rod the "thing" moves.

So it's just a matter of mounting things in the right place.

It may help if you tell us what needs to be moved.

______
Rob

The object needing to be moved is a passive solar heater. Basically a big wooden rectangular flat box, with a bunch of aluminum painted black inside that absorbs heat from the sun.

So how would I attach the metal threaded bolt to a motor? If I wanted the solar heater to move on two different axis's would I need two motors? How about attaching the nut to the panel? Any tips with that? Thanks for the advice man! I really appreciate it. My official project thread is over here http://arduino.cc/forum/index.php/topic,54992.0.html

[Reply #17 on:]

Attached is a quick drawing of the general idea.

As the rod turns the nut moves up (or down) and moves the panel with it.

Note that there are three pivot points (the red dots), obviously the panel, but also the motor and the nut have to pivot as well. This means that both the motor and the nut have to be in a mount of some kind that allow them to pivot. Pretty easy to do.

This is essentially a "linear actuator" done on the cheap.

This can be mounted several ways and may have to be different depending on the clearances, but this was quick to draw.

Another thing to think about is the need to rack in two axis. One of them (the altitude?) only changes over weeks and months an dit's not normally worth the effort to dedicate control gear to that. Either leave the whole apparatus at the optimal angle for you latitude or have a manual system that you adjust every few weeks.

Another thing to think about, you will need an RTC or some method of knowing the time/date etc.
______
Rob

[Reply #18 on:]

Attached is a quick drawing of the general idea.

As the rod turns the nut moves up (or down) and moves the panel with it.

Note that there are three pivot points (the red dots), obviously the panel, but also the motor and the nut have to pivot as well. This means that both the motor and the nut have to be in a mount of some kind that allow them to pivot. Pretty easy to do.

This is essentially a "linear actuator" done on the cheap.

This can be mounted several ways and may have to be different depending on the clearances, but this was quick to draw.

Another thing to think about is the need to rack in two axis. One of them (the altitude?) only changes over weeks and months an dit's not normally worth the effort to dedicate control gear to that. Either leave the whole apparatus at the optimal angle for you latitude or have a manual system that you adjust every few weeks.

Another thing to think about, you will need an RTC or some method of knowing the time/date etc.
______
Rob

Why would need an RTC? Isn't the point of having a solar tracker so you set it and forget it?

I've been thinking that it probably isn't worth the extra effort to make it pivot on the second axis. But I thought for a challenge it might be fun, because eventually I want to create a solar parabolic stirling generator and that requires the 2 axis tracking style system.

Thank you very much for the diagram! It certainly helped me make sense of it all. I suppose I could get an electric motor that has a threaded drive shaft off of it and I could use some hardware to bolt them together. But how do you attack a metal nut to a piece of wood? I could see me screwing a piece of metal to it and maybe welding it? But then again it has to pivot right ... Hrm...

[Reply #19 on:]

Why would need an RTC?

Maybe not because I guess you want to use LDRs to track the sun.

But how do you attack a metal nut to a piece of wood? I could see me screwing a piece of metal to it and maybe welding it? But then again it has to pivot right

Yes it would almost certainly require some welding if you want to do it on the cheap. Not hard but does need some metal fab skills.

You could probably bodge something up, for example a hose clamp can be used to hold the nut, the clamp could be bolted to a plate that is screwed to the wood. The bolt is your pivot point. A search through a junk yard may give inspiration.

I suppose I could get an electric motor that has a threaded drive shaft off of it

I doubt you will find a motor with the rod already attached, normally you couple a motor shaft to the rod.

There's quite a lot involved, even for a "simple" application like this.
_____
Rob

[Reply #20 on:]

Alternatively have you considered simply turning off the pump

Turning off the pump unfortunately will allow water to trickle back through the pump.

Use a check-valve (you make one for a few cents). 
Or use a different kind of pump that prevents back- (or forward) flow.
The combination of a low-performance pump and an electrically-operated valve is going to be difficult to resolve.

Aye I agree. I'm gonna abandon the water pump idea and try the motors with the threaded rods instead. Thanks for replying

[Reply #21 on:]

Do a search for linear actuator.  Here is one I found for satellite dish tracking. http://www.summitsource.com/product_info.php?ref=1&products_id=8220

For your app you need water resistant/proof so it does not fail after the first rain.  I have been looking at them for another project.   You should be able to find what you need for $50 to $100.  Many of them also have a sensor to tell your controller how far they are extended.

[Reply #22 on:]

tjbaudio is right I think wh33t, my "poor man's" linear actuator could be made for next to nothing from junk lying around the garage, but a real one would be a lot better. If you can find one for $50 I'd get it.

AFAIK most only have end of travel limit switches but if you can get one with positional feedback that's good.

No matter what you use you HAVE to have positional feedback.

_____
Rob

[Reply #23 on:]

How appropriate...In todays new products presentation Sparkfun had these:
http://www.sparkfun.com/products/10456
http://www.sparkfun.com/products/10455
You'd best do the research and make sure the pump you have will provide the pressure you need for the solenoid.
As mentioned above garden / hardware / irrigation / hydroponics shops will stock these. Not sure how the prices compare.

[Reply #24 on:]

I would have thought the central heating motorised valve would be the cheap easy way.  Most of em have a switch that gives positional feedback built in (used to fire up the boiler when the valve opens without it opening the valve when the boiler is fired seperately).  Has to beat faffing with threaded rods and linkages. Reasonably cheap and readily available from your nearest plumbers merchants, only possible downside is they are mains controlled. They are free flowing when open and shut tight when closed so don't need any pressure to open them (they need to be with the average C/H pump being a loose fitting impeller in a rough cast housing).

http://www.uk-plumbing.com/honeywell-2-port-zone-valve-v4043h-1056-22mm-p-1410.html