Tuesday, June 18, 2013

brunnhilde's power ports

I considered naming this post "how to make lemonade out of lemon. I decided not to least someone mistake that I put down the cup holder in Taytana's cabin is a lemon. It is not a lemon. In fact it is one of the best cup holder money can buy.

I have always loath the cigarette lighter jack. I don't smoke and cigarette lighter jack is only good for it's original design purpose - to light a cigarette. For used as a 12V power outlet they are big, ugly, and do the job poorly. However often did you find the device is not getting power because the spring loaded contact has jarred loose?

Disclaimer - this post is not intended to be an instruction for modifying the DC system in your vehicle. Should you choose to follow what I did, in part or in whole you are solely responsible for any potential risk or damage that occur.



For my VW Vanagon Camper I had built a custom DC outlet box for the purpose for secure connection of devices. The DC  outlet box also allow me to plug in charger to charge the batteries when the vehicle is under storage for extended period.

this one in my Vanagon Camper has two banks of 12V ports - one for the house battery and one for the starting battery; there is also a rocker switch to turn on or off the doom light with an LED indicator to help you find it in the dark


In Brunnhilde the ideal place for this DC outlet box is where the cabin cup holders are. It happens that one of the two cup holder is defective. Someone at Airstream tried to make it open and close more easily by filing off the length of the plastic spring tabs. Problem is they are filed down too short that they binds the cup holding ring.making it useless.

I have been trying to find a good looking plastic project box for electronic hobbyist that can accommodate the XLR connectors that I have used for many years in the Vanagon Camper. I always subscribe to that constraints are prerequisite for good design and constraints I have here. I didn't want to drive all over town to find a electronic project box so I would try to make lemonade out of a lemon.

A few days ago I was staring at the defective cup holder again. I thought to myself may be I turn the cup holder into the panel for the power port. My initial plan was to install 4 ports. I took some measurements and inspected the hole behind it. Soon I was quite sure despite the shallow depth I can install the almost 1" deep XLR connectors if I just put my mind to it.

the left cup holder has a cutout already - i wonder what Westfalia intended it for; may be the European James Cook have a connection here
 behind the right cup holder does not have the same cutout
 the XLR connectors requires at least 1" depth
i found the grounding point above the DC charger
 a very nice charger for the house batteries as well as the starting battery
i knew the land line phone jack Airstream put in is good for something - I use the cable to feed the new wiring behind the plastic trim
the cup holder front cover has a ridge in the middle - this is the only orientation of the connector that will take advantage of the hole behind it; i just have to go with 2 instead of 4
Actually there was a lot of dremel tool work, drilling, and filing to get the connectors installed. The plastic material of this German cup holder is very thick and strong, and I am so happy that I can re-purpose it for the DC outlet box.It turned out to be a very handsome panel.

i use masking tape to hold them in place so I can drill the screw holes accurately
There are some interesting thing I found in my search for a suitable place to connect the load. I removed the panel where the master shutoff switch for the cabin batteries and I was shock to see this hidden hazard. If you like me find the three seatbelts for the rear passenger a neusance and stowed them out of sight the chance is you tuck them in the gap between the head cushion and the steel box. Guess where the right hand most one sits. It drops down to where the two contacts of the master shutoff switch is.

a potential arc welder hazard - i am not sure it is possible to short one of the terminal post and the back steel frame with the seatbelt buckle but you cannot aford it to happen even the chance is very small
the duct tape at least mitigates the risk

The other thing I discover is the label for the cabin batteries fuse box is not consistent with the numbering of the fuse box. It is transposed 180 degrees. Someone had fallen to this trap and most of the fuse sizes are wrong because he/she relied on the orientation of the label without paying attention to the numbering of the fuses which is on the transparent cover.

i  verified all the fuse circuits by pulling them one at a time and the label descriptions are correct; you can see many fuse sizes are still wrong in this photo
i wonder if someone has flipped the fuse strip 180 degrees when servicing it before; i don't want to stress the cable bundle so i left it well alone as it

one can never stress the importance of properly fusing the load - i used a blade type fuse holder
30A is more than I would ever need

i don't care for big dc-to-ac inverters; my goal is to conserve battery charge so i only use one that is just enough for the job; this one is about 120w but enough to power my notebook, charge the DSLR's battery, and the TV

it can power my notebook and the best part is it has no fan, hence no noise
   i carry this larger one just as a backup
after it served it's purpose the landline jack sole useful life is over - airstream please put me on your do-not-call list as you cannot reach me via the landline phone jack that you so thoughtfully upfitted

a duplex DC power panel
But when you try to unplug doesn't the panel hinge down? I have a solution for that. If you look closer at the photo below there is a self-tapping screw that keep it from being pulled open. The screw takes advantage of one the two holes the cup ring hinged on.

some of the many use cases

the same dc-to-ac inverter powers the LCD HDTV using an adapter cable to plug into the "cigarette lighter" socket
it is normally hidden from view
the dumbing down of public television - they arrange this excellent documentary "Independent Lens" at 11pm so they can put carp at the prime time slots
oh, i have to go over everything Airstream had done, and the holes left behind by the original TV mount is no exception
need me say more
one of the nicer pieces at ikea - these three are new releases; i have to exercise self-restraint to not buy one
Ikea has a new LED fixture that looks similar to the one I installed on the top of the kitchen upper cabinet. It has a motion sensor (seems to sense ambient light change) that may be perfect for the entrance step at the sliding door. It requires no wiring as it is powered by 5 AAA battery. It is cylindrical and has a round cross section about the diameter of a AA battery. I was very tempted to buy one for only $14.99. In the end I resisted due to my general distrust of sensors in low cost consumer products. I am also quite used to climbing in and out of the steps and the light is just solving a problem that does not exist.

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