Sleep Mode?? Effective and worth it?

TJHJ

So I was thinking about a sleep mode similar to an interrupt based wake up pin, but I am wondering if it really would be worth it. I am working on a solar panel sun tracker, ·and at night the chip does not need to be running full speed sampling the sensors.
If I were to stop all cogs except two and have one running

Repeat  until Lightsensor > nightlevel
                Waitcnt(5min +cnt)

And the other

Waitpne(|< Gohome, <| Gohome, 0) &#8216; The go home button to move the panel back to the down position. 
Movehome &#8216; Move motors to put the panels down. 

·

I am thinking that both cogs would effectively be asleep for most of the time. Reducing power consumption, but the prop is such a low power component anyway would it really be worth it? Am I really reducing the power consumption that much over a constant single cog sampling a repeat loop like the following? One cog only here but its running constanly? more power less power? I think more correct me if I am wrong please.

Repeat until lightsensor > Nightlevel or ina[noparse][[/noparse]gohome] == 1 ' so single line repeat loop that stops until the conditions are met. 
If lightsensor > nightlevel 
                Tracksun
If ina[noparse][[/noparse]gohome] == 1
                Movehome

·

What do you all think? Would it even be worth the power saved to kick it into sleep mode? I am thinking that due to the size of the solar panels, 3 6x3 foot panels, they probably would put out enough power based on starlight to keep the prop running no matter what. The concern is that since it needs to run to see when the sun comes back up again, it needs to run, but I don’t want to waste a whole bunch of extra power. Having it run all night looking for the·sun.
edit*
Also what about the life of the prop, would there be long term “wear and tear” from running at full speed for such extended periods of time. Ie failure in a few years? Has anyone even had a chance to find a failure time for the prop?

TJ

Post Edited (TJHJ) : 8/8/2008 5:41:43 PM GMT

Phil Pilgrim (PhiPi)

It might be easier just to keep all your cogs running and switch to a low-speed internal clock during the idle periods.

-Phil

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'Still some PropSTICK Kit bare PCBs left!

Mike Green

As you should be able to see from the Propeller datasheet, the power drain depends primarily on the number of cogs running and the speed of the system clock. It's very easy to switch from the RCSLOW clock to a crystal controlled clock and back again. If you need precise control of timing, you could even switch between PLL1X and PLL16X with the Propeller spending most of its time with a 5MHz system clock.