Build Log 4: The Handle with Handle Handle (and some power supply notes)

A project log for Network Detached Storage Device

Ever wanted a self-hosting NAS robust enough you can throw it in your rucksack and forget about it?

sdfgeoffsdfgeoff 09/02/2022 at 10:410 Comments

It has a handle, so you can pick it up now. Twisting the handle relative to the body is super satisfying as it actuates the latches. It really feels like something you'd have mounted into the wall of some sci-fi vehicle. 

"EMP incoming!" Jacob yelled over the intercom.
I stood up from my station and started running towards the op-center. Maybe I could disconnect the equipment before the EMP arrived. I was just at the doorway when the floor jolted sideways by half a meter and I stumbled against a wall. I could already tell I was too late. Only one activity light was still glowing, and it was flickering in a haphazard mockery of it's normal pattern.
I grabbed the handle of the nearest compute module, twisted it and slid it out. Nothing looked damaged, but I knew that inside the tracery of silicon had been destroyed. We had spares - there were spares of everything, thank goodness, but that'd count on us surviving the next few minutes.....

Ahem, uh, wrong universe. Anyway.... handle. Yes:

Fun fact: the 3D part that's actually the handle (the bit you grab) is ... "HandleWithHandleHandle.stl". yeah.

And that's the battery bank you see in there as well. It's quite large, I'm going to need to make up a custom cable to be able to extract power from the USB ports on the top. How is the battery bank held in? Well at the moment it's just resting there. The easiest design that accommodates the largest variety of battery banks is .... zip ties! Yup. So underneath the battery bank is a platform with some holes in it, and you can zip tie in whatever power source you have.

Another snag with this power bank is that while this battery bank can provide power to the pi while charging, it momentarily disconnects when you plug/unplug it. So I'm going to need some serious switchover capacitors or something.

I grabbed my USB power analyzer (which I really don't trust, it was a $2 purchase), to see how long I expect the battery to last. Here it is with just the raspberry pi and no accessories (this is a pi2):

So that's 1.25W.

The battery bank I have claims 10,000mah (at 3.7v I assume), which is 37Wh. This gives an estimated time of operation of ... 29 hours if everything is 100% efficient. With the hard drive plugged in the current goes up to 0.66A (3.3w), and the estimated battery life drops to 11 hours if everything is 100% efficient. I still have to add a USB Wifi dongle as well.

I'm guessing that at the end of the day we'll see closer to 5-6 hours operation.



Just a teaser. There really isn't much more than what you see in that screenshot. I need to write another story log before I can figure out what software is needed!