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How best to power an offsite backup

Posted: Wed Jun 06, 2018 4:02 am
by jango_22
Hello I am currently prototyping the parts I plan to use for making a rpi based offsite backup server but am having a dilemma on how best to power these items. Idealy I want to power the Raspberry pi, a 2.5 inch hard drive, and hopefully an 80mm 12v fan. at this point my thinking is to use a 12v 2amp power adapter to a barrel jack and split that two ways inside the case. my plan is to then use a stepdown buck to step down to 5v 3amp for powering the pi, and a leave the other 12v for powering the fan.

currently While I configure software and acquire parts I have been using a 2.4 amp usb power adapter to power the pi but it still seems to have a hard time just powering itself and the drive. Would this be helped by using that buck with the 12v adapter? or is the pi always going to have low voltage warnings while powering a major peripheral?

What do you think the best option for powering these three devices would be?

Re: How best to power an offsite backup

Posted: Wed Jun 06, 2018 7:31 am
by Z80 Refugee
Your current difficulties with the 2.4A adapter may be simply the length and thin-ness of the connecting wire. It's not just a question of resistance, the longer the wire is the greater its inductance and this reacts against the peaky nature of the RPi's current demand to cause even greater instantaneous voltage drops.