ideas welcome! arduino UPS / Sleep / wakeup

[ianmorris1960]

Hi, I have built a factory data collection machine, the circuit is involved, but that is somewhat unimportant..

a requirement is that ist is able to store data when the 24v supply is interupted.

It recieves power from the factory plant (24v) it has sensors from the plant, an arduino clocks the inout, and stores it in a time based table - say 1 minute buckets.

The unit is polled periodically via RS485, when it transmits the data collected to a PC which then sends the data onto a sql database to provide a dashboard for anyone who is interested!

Suffice to say it is split into two parts, 24v to 5v to deal with sensor inputs, display and comms. should 24v feed stop, there will be no data caoming in, the local display is pointless and the comms just uses power so stop that.

What matters is to preserve the data stored in the arduino - nb, using the nvram is not an option, it would soon exceed the 'warranted' write cycles.

So, I am using a powerboost and a lipo battery, the set up is that the 24->5v powers the powerboost, which charges the lipo, then the boost section provides the 5v for the arduino only. This seems to work well.

I would like to send the arduino to sleep whilst there is 24v supply.

Sounds like a UPS! well really that is what the powerboost is in this application

I have toyed with, and tried various mechanisms but none have proven viable.

Important the board is a Leonardo - I just had some to hand!

How would others approach this?

Thanks in advance

Ian