NXT hibernation

[entozoon]

I've built a robot that opens the curtains.. and as I found out this morning, the batteries don't last overnight.
I was wondering if there was a more efficient way for the NXT to wait overnight other than a simple thread.sleep(x) ?

(I realise I could connect it to a PSU but electricity bills are expensive >_< )

[skoehler]

As far as I know, leJOS 0.9.1 will come with a firmware, which puts the NXT into a deeper sleep state, if there's nothing to do. So if all Threads are sleeping, the NXT's CPU is sleeping as well. Also, it has been observed that putting the motor in float state consumes less energy than having the motors in break mode. And I believe the little AVR co-processor which assists the big ARM CPU cannot be suspended as well. Even though enhancements were made, the NXT will probably not last all night. As far as I'm aware, there is no low-power wakeup timer inside the NXT. Also, I wonder why you think that using an (efficient) PSU is worse than charging the batteries the next morning.

[entozoon]

That's fascinating! I'm looking forward to the new firmware then, I think i'm still running 0.8.5
And putting the motors in float is a great idea.

I just thought that leaving the psu plugged in might waste energy.. the transformer heating up and stuff. Perhaps I'm wrong then?

[skoehler]

I just thought that leaving the psu plugged in might waste energy.. the transformer heating up and stuff. Perhaps I'm wrong then?

The modern PSUs (not the ones that work electrically, without coils) are pretty efficient. Also, by charging a battery will consume more energy then there is afterwards in the battery. I'm not sure either, but I'd bet that a modern PSU wins compared to charging/using batteries. Also the charger itself needs a PSU.

[entozoon]

Thank you very much for your help!

I suppose the best thing would be a clockwork device to press the on button and have it run as the default program.. if only I was a clockmaker