HB5050 Appreciation Page

The Box

One of the most commonly boxes used by Air-Stream members a basis for an enclosure is the Jaycar "HB5050" Sealed Aluminium Die-Cast Enclosure. It measure 222 x 146 x 55mm and is rated to IP65. These boxes provide effective weatherproofing and EMI/EMC/RFI shielding. They conveniently fit at least one Mikrotik RB433/RB433AH with MiniPCI cards. With careful planning, two RB433 sized boards can be squeezed into one enclosure.

The Modification Process

Converting the basic box into a outdoor pole mount enclosure for a typical outdoor installation requires some work. The basic steps are:

1. Drill one or more ~15.5mm holes for N-Type connector bulkheads
2. Drill one 20mm hole for the Ethernet cable feedthrough (to suit Jaycar cat no. HP0732)
3. Create grounding points for MiniPCI cards that have ESD protection
4. Make up an L-shaped bracket from aluminium with drill holes on one face to suit your selected U-bolt
5. Rivet the other face of the bracket to the top of the enclosure
6. Using either a template or a real board, adhere some PCB stand-offs to the bottom of the box to suit the board mounting holes using an appropriate epoxy
7. Wait for epoxy to dry then screw host board to the standoffs
8. Insert MiniPCI card(s) and connect ESD protection grounding wire(s) to box
9. Insert and connect N-Bulkhead pigtail(s) then tighten
10. Feed Ethernet through the cable feedthrough and plug into Routerboard then insert and tighten the gland
11. Insert the rubber seal provided with the HB5050 into the lid
12. Power on and test before screwing on lid

One rule to try to follow is to not drill any un-necessary holes in the box. This is why the standoffs are glued to the base rather than screwed in from behind. The screws require holes which may compromise the IP65 rating of the box. The holes for the N-type bulkheads and cable feedthroughs are acceptable because those parts are also IP65 or IP68 when mounted correctly. The guide below below is only one variant of what can be done and indeed there are many improvements possible.

Step-by-Step Modification Guide

The first step is to drill, cut or punch the large holes. The image below shows two holes drilled for N-Type connectors that were drilled with large drill bits and a larger hole that was cut for a cable feedthrough. Burrs have cleaned up using a Dremel. All holes for connectors or cables should be drilled in face of the box that will eventually be facing down towards the ground. This provides another layer protection from the rain and sun above. For a RB433 enclosure, the most common side is the long edge.

If you have the ability, a more elegant way is to cut the N-bulkhead holes to the following shape. This will give the best seal and stop the connector moving while you tighten the nut later.

If you would like to take advantage of the ESD protection of your MiniPCI card (eg Ubiquiti XR2, Mikrotik R5H) you will need to create some kind of connecting point for the grounding strap. This is where you might make one exception to the "no holes" rule by providing a hole for a grounding screw and nut. Make sure this is then well sealed over with epoxy or RTV.

For at typical installation there will need to be some way to attach the enclosure to a pole. This can be done with an L-shaped bracket along the top (ie opposite edge to where you drilled the connector/cable holes) of the enclosure to "hang" the box off. The L-bracket is then attached to a pole with an ordinary U-bolt. This can be any L-shaped piece of metal you have lying around. The image below shows cutting a length of metal from an old roller door guide.

This is what the bracket looks like after it has been cut and de-burred. One improvement to this picture would be a bracket that is the entire length of the top edge. The reason for this is that you can then rivet the bracket into the three screw posts of the box. The design shown here will break the 'no holes' rule later because of this small bracket. Drilling halfway into the screw posts without breaking through to the inside of the box avoids breaking this rule.

Using your U-bolt bracket you can mark where to drill holes into the L-bracket.

After drilling the holes.

Testing that the U-bolt fits through the holes.

Conveniently this bracket already had holes drilled in it just the right size for 3.20mm rivets. It was just a case of selecting a few and drilling holes into the box. Notice that the L-bracket will be mounted flush to the back of the enclosure.

As mentioned above, an improvement would be to use a longer bracket and rivet only into the screw posts by drilling through into the middle of the posts at the locations shown on the image below (but not all the way into the inside of the box.) On this box, extra epoxy was used to totally seal the rivets on the inside of the box.

Using the rivet gun.

The bracket rivetted to the enclosure.

Prepare standoffs. The ones shown here are 10mm long.

An easy way to locate the standoffs in the correct location is to use an actual board. Loosely screw the standoffs to the mounting points as shown below.

Then deposit a blob of epoxy on each standoff.

You could also use an actual-size template to work out where approximately to put some extra epoxy on the base if you want adhesive on both sides before attaching. This will also help align the board to the exact location you want as you need to have enough clearance for the MiniPCI card on one side and for the RJ45 connector on the other.

Carefully insert the board into the box and line it up to the location you want then gently push downwards on the board to push the adhesive together.

After allowing the adhesive to dry, it might be a good idea to remove the board to easily plug in the RJ45 connector. However if you have designed the board location well there should be just enough clearance to, with some convincing, plug in and remove a RJ45 with the board in the box while still having enough clearance for the MiniPCI card on the other side. This will only work with basic crimped RJ45 connectors, not the ones that are moulded with boots. Make sure you feed the cable through the cable gland before plugging it into the board.

You are now able to screw the board in. Do not tighten too much as the stand-offs are only glued in.

Now you can insert the MiniPCI cards. Attach the grounding straps from the MiniPCI cards to the grounding point that you previously prepared.

Disassemble the N-bulkhead pigtail and insert it through the hole. While the pigtail is loose, plug the card end into the miniPCI card. Find some way that it plugs in without having to twist the coaxial cable. This means you might have to rotate the N connector in its socket and/or make a loop in the cable to get the plug to line up with the card connector without having excessive cable twist. Once this position is found plug the pigtail into the card then, without rotating the N connector from its current position, attach the washers and nut to the N connector and tighten.

Test the board making sure the wireless card(s) works.

Insert the seal provided with the box into the groove into the lid. Make sure there are no gaps. For an extra safety measure, make sure the start/end of your seal is in the long edge of the lid and when the lid is place on the box, put that long edge at the bottom edge. You could also smear a small amount of appropriate silicone sealant over the area where the start/end join is.

A U-bolt can be used to attach the box to a mast as shown below

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Below are some more images of modified HB5050 designs

TBA