I wish to place some Raspberry Pi's in remote locations (data centres) for telemetry and other services like serial OOB access.
Typically dual AC feeds are presented to customers in a data centre which come from completely separate feeds from the local power grid. Raspberry Pi's take a single DC 5v 1mA input. In the event that one of the power feeds in the data centre goes down I want the Pi to stay up (and in the event they both go, it will have a battery pack).
This isn't a natural feature of the Rasp Pi (two power supplies) so I need to design a safe and fault tolerant system that will do this. My knowledge of electronics is limited and I will be consulting others and testing in a lab style environment; As a basic premise though, does the following sound sane or a have I grossly misunderstood electronics and risk exploding all the kit in my rack and potentially others;
- Dual 16A or 32A feeds per rack (A and B feed)
- Attach a regular 5v DC Rasp Pi transformer to each feed to present two 5v DC feeds
- Attach a diode to each feed to stop any current passing back towards the source A or B feed
- Attach a polyfuse in case of a surge coming in from the source A or B feed
- Attach A feed to Rasp Pi battery pack, then to Pi 5v inpit
Attach B feed as the power supply to a powered USB hub, which is then connected to Rasp Pi USB port (A Rasp Pi can be powered by either it's main USB mini power input, or voltage coming from a powered USB hub, both together as far as I have read, won't harm it)
A Feed B Feed | | DC DC Transformer Transformer | | Diode Diode | | Polyfuse Polyfuse | | 5V DC 1mA USB Hub Battery Pack Power Input | | Rasp Pi Rasp Pi 5V Input_________________USB Socket
I understand this question is somewhat Rasp Pi specific, but in terms of general electronics, would this work? What should I be looking out for on the Rasp Pi that could cause this plan to fail?
My main concern is that I will connect the A and B feeds directly together and blow everything attached to both feeds. Also, what if the A and B feeds are out of phase as they are coming from two different sources?; I assume this doesn't matter as they are both being converted to DC?
Many thanks and sorry if this seems silly, my knowledge of electronics is very limited.