"Turn on when sufficient power available" (& back off) ...

[Photon939]

I noticed with hubs that if there isn't enough power some or eventually all of the USB sticks stop working, without ill effects seemingly.

Also I recall reading about bitfury's chip that he designed it specifically to be able to gracefulyl degrade in hashing power as it gets less electricity. So maybe his chips would be the best for this type of application.

If hubs would shut off individual plugs when they don't have enough power that would be great, but I think what is tending to happen instead is all the sticks get iffy when there is not enough power coming into the hubs. Having lots of hubs would likely end up with all of them not getting enoguh power so nothing working. So even just switching entire hubs in and out would be an improvement over that.

Maybe I will have to get a solar panel and a car battery and experiment a bit.

Though the arduino idea seems decent too at first glance.

Its possible I won't need to deploy until early spring or late winter, depending on difficulty increases. (Grid power here is $0.14 to $0.15 CAD.)

-MarkM-

Yes you would still need the arduino setup to handle the load shedding, otherwise the voltage supply would droop and cause problems for the whole system. Switching power at the hub level would be much much easier although would make the load switching more granular. All depends on how in-depth you want to go I suppose

[markm]

Maybe this would work, with car batteries:

http://dx.com/p/battery-voltage-over-voltage-under-voltage-detection-sensor-module-for-arduino-152322

Turn on a hub when car battery is fully charged, turn it off when battery is not fully charged.

Not sure though how one would measure just the battery charge, without the power from the solar/wind stuff that presumably is also connected to the battery's terminals also getting measured at the same time / confusing the measure.

Oh maybe it disconnects the charger from the battery, measures the charge, then reconnects the charger, or something like that, hmm...

-MarkM-

[Photon939]

You don't need external hardware to measure the battery charge, you can do that with the arduino's built in analog inputs. (using two resistors for $0.20)

Assuming you're using a charge controller with the solar panels and battery, you can determine how much power is available just by looking at the battery terminal voltage (even with loads actively connected)

A fully charged lead acid battery with no charger will sit at about 12.6v, whereas if the charger is actively running a float charge you'll see voltages around 13.6v,  You can use that to tell how much power capacity you have in the system. If connecting a dummy load doesn't cause the battery voltage to drop below a float charging state then you're good to go to bring a hub of erupters online, etc

This also works in reverse; if the battery voltage drops out of float charge while loads are on, then you want to begin shedding loads until you get back to a float charge or all loads have been turned off

[markm]

Nice, thanks!

-MarkM-

[markm]

So a timer, again. We already covered timers, thanks.

-MarkM-

[klondike_bar]

a basic controller that can determine voltage from your panel and the current battery capacity should suffice. Once one or both those reading pass a certain limit (use a relay for this), the relay will switch the main line ON for your devices.

turning off is different though, as it may be difficult to 'slow' or 'stagger' the OFF mode. If using a relay, once the lower threshold is hit the circuit will turn off.

relays typically have a range for activation though. for example:

I have a 12v / 120v relay. when it has >10V it turns on the 120v line until the sense voltage falls below 8V. maybe something similar from your panel?

[markm]

A multi-pole relay maybe, so that it would be in parallel with a dummy load until it plus the dummy adds up to enough, then it switches power from the dummy load to the real load and also switches in the next relay that will do the same when even more power becomes available. Oops but that is another dummy load on the syste in addition to the real load that just got switched on. I guess its not a simplistic problem.

But relays apparently don't just throw and stick, they need power constantly to stay thrown, so would consume some of your power all the time. I have to go look up MOSFET as apparently those are better than relays, someone posted earlier.

-MarkM-

EDIT: I looked at the arduino, and it was far from obvious how to go about "simply" using it to do this stuff. I think it could become a seriously useful product to offer though, as mining moves toward being mostly a seasonal or time-of-day activity as difficulty keeps going up and up and up...