Possibility of adding a shutdown battery

[Caine]

Hi guys,

I was looking for a low-power server platform when I stumbled upon the plug computers. I've read that you need to remotely issue the shutdown command to turn the plugs off.

I had the idea of adding a small rechargeable shutdown battery.

This battery should be capable of powering the device for only a couple of minutes (2 would already suffice). Furthermore, the OS should be capable of determining the battery level and if the device is plugged in or not. Whenever the plug would be running on battery and drop below e.g. 50% capacity we can issue an automatic shutdown command. Plugging it back in would restart the plug (and recharge the battery).

Advantages:
- Easy starting/stopping interface, just plug it in or out.
- Automatic clean shutdown and restart whenever the power fails.
- You can quickly plug the computer into another socket without losing connectivity.

Unfortunately I'm no hardware expert, so here's my question.
Can this be hacked onto the existing board? If not, any chance of seeing this added in the future?

Thanks,
-Caine.

[dattaway]

Unfortunately I'm no hardware expert, so here's my question.
Can this be hacked onto the existing board? If not, any chance of seeing this added in the future?

A tiny, cheap 9 volt NiMH battery into a simple 3 pin 7805 regulator's output right onto the sheeva's power supply ought to do the trick.  Have some resistor or something trickle charge the battery and it should be good to go.

[jlpoole]

Having temporary power to shutdown is very desirable.

The plug is designed to run in non-server secured environments, and as such, will be subject to intermittent power interrupts.  The risk of software being thrown a curve ball because shutdown was not properly had argues in favor of having a simply battery port based on the suggestion herein.  I'm hoping the engineers monitoring this topic will consider such an option for future releases.  I often worry about the status of matters when I return to my office where I have a plug running and it probably has been subject to a sudden power outage.

[Abra]

it would be nice indeed.
dattaway, with your suggestion, will the software be aware of the fact that it is now running on battery power (and how)?
thanks a lot

[UnaClocker]

You'd need some kind of USB adapter with an ADC port on it, and a voltage monitoring circuit hooked from that ADC to the 9v battery. Then you'd need a daemon running on the plug that monitors that ADC port and issues the shutdown command when the voltage reaches a preset level.

[MarkF]

Since the GPIO are somewhat accessible, I believe a TWI (I2C) solution could be built instead of using up the only USB port for the ADC.  It would also be cheaper.

For the second part (software), adding a "driver" to the NUT stuff (Network UPS Tools) to support something like this would be pretty easy.  After all, you are describing a UPS with a very small battery so it fits perfectly into the paradigm.

My real-life solution has the plug, a powered USB hub, a GigE switch and another server powered by a single UPS.  The UPS provides feedback to the NUT enabled plug through a serial to USB converter.  The plug sends alerts to the other server (also running a NUT client) when the power goes low and both shut down.