Author Topic: Mounting my Raspberry Pi  (Read 3048 times)

Offline lrhorer

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Mounting my Raspberry Pi
« on: February 24, 2015, »
This is hardly Earth shattering, and likely not all that original, but I thought I would share my idea for mounting the Raspberry Pi controller for my show.  I'm not going to get compulsive about cables and boxes in the yard, but I figure anything that makes additional use of an existing rain-proof enclosure and reduces the number of cables running around the yard (not to mention that have to be stored when the display comes down) is a worthwhile effort.

What I decided to do was mount the Raspberry Pi computer and DMX controller inside the case of my primary Lynx Express.  Currently I also have a Bluetooth adapter in there in order to drive a pair of Bluetooth loudspeakers, and I am looking into possibly getting an FM transmitter, as well.  I went to a local plastic supply and purchased a 9-1/2" x 10" piece of 3/16" Lexan plastic ($5) to provide a flat mounting surface.  In addition, many adhesives, including common industrial adhesives and Cyanoacrylate glue stick really well to polycarbonate plastics and sometimes not so well to PVC.

For WiFi access, I purchased a Rosewill RNX-N250UBE USB / WiFi adapter, which was reported to get good performance and to work with the RPi out of the box.  I also obtained an Insignia four port USB hub, because I need at least 4 ports for all the devices, and the RNX-N250UBE obscures the USB port adjacent to it.

Here is the process:

After removing the lid from  the enclosure body, lay the plastic plate in the lid of the LE housing and drill a hole at each corner securing the platform into the lid.  Insert some 6-32 screws into the holes in the lid and waterproof the mounting points with some Silicone Sealer.  Measuring and placing very carefully, use CA adhesive (superglue) to attach one of the cheap indoor 3 port extension cord outlets to the Lexan so that when plugged in the Raspberry Pi power supply just misses the LE heat sink and the DC power supply of the LE when the lid shuts.  The vinyl of the plug will stick instantly to the Lexan plate, so take great care in placing it.  Place four 1" adhesive backed Velcro pads to the back of the case of the Raspberry Pi.  Making sure there is enough room to get to the micro-SD card, apply the RPi to the Lexan as close to  the extension cord head as possible.  Let the RTV sealer cure overnight, and then remove the Lexan plate from the lid.

Attach the WiFi dongle to the lower middle port on the Raspberry Pi B+.  If you are going to use the RNX-N250UBE, then use the following procedure.  Mark two points directly below bases of the twin antennas of the RNX-N250UBE.  Remove the RPi, drill two significantly oversized holes in the mounting plate, and  then mount the RPi back on the plate with the antennas pointing away from the mounting plate.  Setting the plate back in the lid, carefully mark the point below one of the antennas on the inside of the lid.  Removing the plate again, drill a small pilot hole through the lid.  Turn the lid over, measure the distance between the antennas, and mark the spot where the second antenna will penetrate the lid.  Bore two slightly oversized holes in the lid for the antennas.  Removing the RPi from the plate yet again (gotta love Velcro!!), place the plate back inside the lid and secure it with four lockwashers and nuts.  After flipping the antennas around, pass the antennas through the holes in mounting plate and the lid and push the RPi onto the mounting plate one last time.

At this point, I bored a 15/16" hole in the side of the enclosure body just above where the AC cords exit the case using a step drill bit.  I then inserted a 3 pin female XLR  panel mount connector into the hole.  It formed a press-fit, rain proof seal.  I obtained some adhesive backed saddle cable clips and placed them along the sides of the enclosure going toward the hinges and then up towards the DMX input and output ports.  I then soldered a short Cat-5E cable to the XLR connector, routed it along the side of the case, and plugged it in to DMX Output #1.  I prefer this approach because

1.  Many of my lighting fixtures have XLR connectors, and XLR cables are cheap and easy to find.
2.  Using an Ethernet cable either means threading the cable back-and forth through the feed-through of the LE housing, eventually wearing it out, or else leaving the cable in place where it presents one more piece of spaghetti with which to contend while storing and deploying the unit.

Place adhesive backed clips around the sides of the lid to aid in routing cables.  (I used saddle clips, but you can use tie clips or whatever you like.)  Route the extension cord to one of the AC power inputs, cut it to length, and insert it into the tie points.  Mount the DMX controller and route the cables to the RPi (or the hub) and the DMX input of the LE.  Plug in whatever other USB peripherals you will need.  There is probably enough space to mount a Lynx wireless controller in the lid, as well, and it should be possible to power it from the second port on the extension cord, but personally I was leery of putting WiFi, BlueTooth, and Lynx Wireless transmitters and receivers all in such close proximity.  I may give it a try, however.  Once you are certain the Raspberry Pi is no longer likely to have to move, a little Silicone Sealer around the antennas will rain proof the enclosure again.









« Last Edit: February 24, 2015, by lrhorer »

Offline tbone321

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Re: Mounting my Raspberry Pi
« Reply #1 on: February 24, 2015, »
Are you sure that you want to expose your Pi to the outside environment?  While you enclosure may be rain tight, it is not air tight so you may still have issues with condensation.  You may want to include a small heat source in that enclosure like a C9 or two that are on all day and night to help prevent that.
If at first you don't succeed,
your not cut out for sky diving

Offline lrhorer

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Re: Mounting my Raspberry Pi
« Reply #2 on: February 24, 2015, »
Well, I have to.  There's really not much choice.  The question is, "Do I put in the enclosure with the Lynx or in a separate one?"  Either way, it's going to be outside.  Not only that, but when it comes to putting equipment in jeopardy,  the RPi is considerably less expensive to replace than the electronics in an LE.  Nonetheless, your point is well taken.  I suspect, however,  that even at idle, the heat produced by the LE, the RPi, and the associated electronics will be enough to prevent condensation inside the enclosure and in particular on the electronics themselves.  When I get home tonight, I'll put a watt meter on the unit to see just how much heat is generated at idle.

Offline tbone321

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Re: Mounting my Raspberry Pi
« Reply #3 on: February 24, 2015, »
I can't speak for all of the components but the LE runs dirt cold when idling and I don't recall the Pi putting out much heat either. 
If at first you don't succeed,
your not cut out for sky diving

Offline CaptainMurdoch

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Re: Mounting my Raspberry Pi
« Reply #4 on: February 24, 2015, »
Nice writeup.  I have seen pictures of enclosures with a Pi shared with a pixel controller like this but never with a LE that I can recall.

Offline CaptainMurdoch

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Re: Mounting my Raspberry Pi
« Reply #5 on: February 24, 2015, »

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I can't speak for all of the components but the LE runs dirt cold when idling and I don't recall the Pi putting out much heat either.

Yeah, even at 100% CPU utilization the Pi is generating less heat than a C9 would and you probably won't see the Pi at 100% utilization anytime.  I agree with the OP though, the Pi is cheaper than the LE and much easier to replace.  :)

Offline tbone321

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Re: Mounting my Raspberry Pi
« Reply #6 on: February 24, 2015, »
While true, the LE was designed with these conditions in mind and the Pi was not.  As I said before, one or two C9's in the case lit up all the time will generate enough heat to keep the condensation out or at least off of the Pi.
If at first you don't succeed,
your not cut out for sky diving

Offline lrhorer

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Re: Mounting my Raspberry Pi
« Reply #7 on: February 24, 2015, »
The Pi, DMX dongle, and LE at idle are consuming 5.7W, which is nearly as much as a C9 bulb.  If I mount a Lynx wireless TX/Rx module in the lid, that's another 2.1 watts, which puts it just above the heat dissipation of an incandescent C9 bulb.  Right now the case is sitting closed in a 72F (22C) room, the temperature of the Pi board is 94F (34C).  Obviously, sitting outside in temps that may be close to or even below freezing, the temperature in the case is going to be much lower, but raising the ambient temperature inside the case lowers the relative humidity, which in turn raises the dew point.  At the same time, the Pi itself should be running at least 10C above ambient (as it is now), so I don't really expect any issues with condensation.