Topic: "Turn on when sufficient power available" (& back off) ... (Read 1690 times)

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...

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?

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

-MarkM-

Nice, thanks!

-MarkM-

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

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-

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

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 enough 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-

The idea would to be not discharging the batteries at all under ideal conditions, only using it as an intermediate buffer during short dips in solar output.

Alternatively, if the mining computer had a backup supply (easy for something low power like a raspi) then you could eliminate storing any power for the miners (and hope that CGminer deals with frequent usb comm errors gracefully)

Car batteries also are not deep cycle though, supposedly one wants deep cycle types of batteries for this.

Still, I guess in a pinch a bunch of old car battiers would be used outdoors if they would be kept pretty much charged all the time, thanks.

-MarkM-

Well cars don't start in winter a lot of the time, people use block heaters if car isn't going to in a garage.

Indoors well insulated seems to conflict with well ventilated, so I am thinking marine batteries or whatever, ones that don't have to be ventilated? Lithium ion even maybe? Expensive but that is why I am trying to figure out how to minimise the need for them.

It would be really cool to be able to make actual products, "solar/wind miners" that have pretty much everything they need except the actual solar panels or wind turbines, I imagine there could be a market for such things. Or even leave out the actual miners and make units that have USB and ethernet connectors for people to plug in end-of-life ASICminer and Avalon gear to, with 12 volt power plugs modular or somesuch.

-MarkM-

Pretty sure UPS software + usb/rs232 can do what you want... shutdown a system when the battery reaches a certain level and turn computer back on when it reaches a certain level. You might look at some of the higher-end APC models.

Oh I see, it would be hard to do a setup like that. And remember it's dangerous to keep the batteries in enclosed areas because hydrogen (from battery's electrolysis) is highly flammable and can cause a disaster. Make sure to put your batteries in a well ventilated area.

Try to look up the link I posted above. As it is a grid <---> solar/wind controller.

I am thinking probably have enough battery to power the master computer that runs cgminer or whatever, that could go on at early dawn and off in late evening or something on a timer, maybe it could be a laptop or something similar to a raspberry pi but without the pi's inability to properly handle some (such as 3.0) types of USB hubs. Also some battery power to cover a few minutes of cloud or birds etc.

Then have all the hubs, or even each USB miner, be what go on and off based on power available.

I will look up the various references people have given, thanks.

Lead acid in winter might have problems here in Canada if outside, or actually maybe even inside since the mining operation itself would be the only heat in the place...

Is cold going to be a big problem for pretty much all kinds of batteries?

I have coded in machine code and assembler as well as pretty much all generations of languages since, so a bit of coding should not be a big problem.

Though maybe a nice idea would be to make units as a product people can easily plug cheap solar panels into, and have someone actually put support for them into cgminer etc software...?

-MarkM-

It's a much better option although you've made it clear that it's not an option due to the age of the wiring and cost to bring it to code.



As far as doing the sequencing forget about using a UPS, you would end up replacing the lead-acid batteries frequently and it seems you want to avoid batteries completely at this point.


As far as off-the-shelf components go, I am not aware of anything that would do what you are requesting. Adjustable voltage switching relays are available, but without any kind of "smarts" and control logic behind them, they would end up oscillating and repeatedly switching loads on and off during periods where there is more power available than what is being used but not enough to support an additional load.

You will need a temporary source of power though, and ultracapacitors will be prohibitively expensive if you are planning a decent size system. A lead-acid battery would be a good candidate here as it would really only be handling temporary brownouts (small passing cloud, etc) and would not be deeply discharged.

Without it even blocking the panels for half a second would kill your mining setup and frequent power cuts will quickly corrupt the OS on your mining controller.


Back to the sequencing logic - if you want to take a bit of time to learn basic microcontroller function you could implement it easily with an Arduino and something like this http://dx.com/p/8-channel-5v-relay-module-board-for-arduino-red-156424

Combined with a raspberry pi running CGminer (bfgminer doesn't seem to support hot-plugging currently) you could wire the relay board to switch the +5v rail to the usb ports on a modified USB hub.

The arduino can read the system voltages by using a voltage divider with the arduino's analog to digital converter pins

Current sensing and power reporting can also be done with items like this http://dx.com/p/20a-range-acs712-current-sensor-module-for-arduino-148656

You can get digital controllers if you have extra bucks to spend. You can start researching from this item:

http://www.alibaba.com/product-gs/805984391/Saip_group_12_24V_solar_grid.html

Yeah for really rough guess stuff a timer switch would work.

But if it only turned on enough stuff to eat the power an overcast, no-wind day provides, it would miss out on all the power it could be getting when a sunny, windy day happens along.

In other words it doesn't adapt to the actual conditions prevailing at the time.

Even just some kinfd of porch light switcher, if it could be tuned for how much light/dark to switch at,, would probably be better than that, as you could have banks of miners each one triggerd by brighter light than the previous one so on dull days only some would come on, whereas on bright days all would come on.

Not sure though if porch light switches have enough adjustment range to make them not come on on middling-bright days, only on the very brightest days.

Oh and of course their logic would need reversing, maybe double pole double throw switch or something, so they go on in day off at night instead of vice-versa.

-MarkM-

Audio triggered switch is a very bad idea, it beeps from time to time so it would switch on and off. To automate it, it would be easy to use timer switches. 12 hours on the solar and 12 hours on the grid.

Have you seen some timer switches on your local electronics store?

So we need an audio-triggered switch of some kind to listen for the beep?

-MarkM-

Very Easy. Use UPS. when the inverter marks fail (drained battery) UPS takes over, you hear the beep, plug it back to the grid.