Monthly Archives: January 2015

Custom Weatherproof Power Supplies

20150126_14115820150126_145553I like to say “If it were easy, we would’t make the big bucks”. That’s tongue in cheek, but the point is that engineering jobs are never straightforward. I need to supply 144,000 mAh of capacity at 5 VDC to power an accelerometer for a month. Naturally, this is going to be on the ocean, in winter, so the power pack and power transmission lines need to be water proof and robust.

So here’s what I chose. A PVC pipe housing, two parallel 6-packs of D-cells in series (9 VDC) regulated to 5 VDC with a low dropout voltage regulator. I’m using Bulgin fittings sourced from Mouser and rated to IP-67. I machined some PVC rod so that one end will fit perfectly into a PVC cap (bonded with -J-B Weld) and one end will slide with very little clearance down the PVC pipe. I figure this will be bouncing around so I don’t want the batteries to be taking those hits. I used a small proto-board from Adafruit to parallel my battery packs and run it through the voltage regulator up to the cap fitting.

Before building these I did a test outside with one pack of 6 D-cells and only logged 20 days of data. I think the cold does a number on the alkaline batteries, but they also pack some convenience and capacity. I’m going to be swapping these out in the field periodically so I want to be able to drive up, swap power supplies, pull down some data, and move on. These packs will work well for that. I just started a second test outside in hopes of getting the full 30 days of data.


Felling a big cherry tree


I had a good time felling this cherry tree. It was an old dead one and the hawks would perch in it, so her day came. It got to the point where my hinge was nearly gone and I had felling wedge in my back-cut driven pretty deep. There was plenty of space for her to go any way, but I didn’t want to get trapped if it went the wrong way because it was right on a stone wall. So, I ended up removing the last few fibers with a hand saw, then they started popping and I had plenty of time to move safe ground to observe her fall. Turned out some vines were holding on up high, going horizontally to some other trees and shrubs. I think that is why it didn’t fall easily.

Fun cutting though. I just got a drawbar for the tractor too so I skidded the logs up to the barn for bucking up in spring.

Entering the New Year

Lots of activities going on to kick off the year:

  • On the homestead we now have a plan for the garden – ordering seeds soon.
  • Installed the second Layer Light for the girls up at Mimi and Bobo’s farm. One more is almost complete, hitting the market soon.
  • It’s COLD, looking for feedback on whether or not to supply heat to the hens.
  • Lot’s going on at work – Currently designing power supplies and data acquisition units for at sea testing in a few months.
  • Tried my hand turning PVC on the lathe at work – easy day – awesome results.
  • Bogart is growing up to be a very jumpy great pup, we look forward to working with him.
  • And the Navy…lots going on here too, working on nailing down the AT for this year.

Look for updates on the Layer Light to come soon.