Base Station - Utah-WiESEL/wren_wsn GitHub Wiki
The PCBs that make up the base station are called Blades. Each Blade can hold up to 10 motes and a fully populated base station can support 100 motes. The Blades are designed to be modular and most can be used interchangeably; with only the first and last on each base station having different pass through resistor configurations for addressing. They easily connect using 8-pin connectors and are mounted on a wooden support structure.
There are several aspects of the support structure that help the base stations maintain an ease of use and a simple interface. This wiki page provides detail on each component of the base station and the assembly process.
###Table of Contents Base Station Vector Layers
##Base Station Vector Layers (Illustrator File)
The following will explain the purpose of each layer used in the base station design. The designator in brackets in front of each layer name is used to specify the layer in the Construction section. These layer names correspond to the layers in the Adobe Illustrator file.
The layers make up the main support structure of the base station. They can be grouped into three main sections: the base, spacers, and support. The base is what the PCBs, PSU, and programmer mount to. It can be used as a preliminary test bench before the supports are attached. The spacers are used to ensure the proper row and column alignment of every PCB and connector. The support layers are used to keep the motes vertically in line when being plugged into and out of the Hirose connectors. This prevents the motes from damaging the connector by bending it too far one way or another.
Small screw holes are cut in each layer to align the components and avoid damaging the wood when mounting.
###Base Station Layers
#####[A1] Base - Bottom
This layer is the bottom of the base station. There are no cutouts for the dowels because it helps support the weight of other base stations. The stack legs will mount directly to the underside of the base station.
#####[A2] Base - Middle
The middle layer is used as structural support for the base station. One low weight iteration of the base stations omitted this layer, but warping was much more pronounced with only two base layers. The large, round cutouts are used as side wall supports for stacking other base stations.
#####[A3] Base - Top
The top of the base layers is what the Blade PCBs will mount to. The cutouts are designed to match the through hole components on the blades and various programmers we are testing. This ensures each PCB sits flat on the base.
#####[A4] Spacer - PCBs
This spacer is used in between each blade PCB. Its main purpose is to keep the next spacer and support structure from bowing downward in between each blade. It also provides a more rigid structure.
#####[A5] Spacer - Hirose
This is the most important spacer for aligning the Blades prior to mounting. It will make sure the PCBs are mounted such that the motes have no problem fitting through the support structure.
#####[A6] Support - Bottom (x2)
This layer is the first support structure for the motes when plugged into the base station. A second copy is added directly on top to provide clearance over the Blade interconnections for the top support.
#####[A7] Support - Top
The top support structure extends over the top of the Blade PCBs. This provides protection from accidental contact. The third support layer also maximizes protection for the Hirose connectors when handling the motes.
#####[A8] Stack Legs
These are used with pegs when stacking multiple base stations. The additional elevation protects the base station from spilled liquids. They can also come in handy when lifting the base station because the bottom is easily accessible.
###Extras
These are not necessary in the construction of a single base station, but add additional features if desired.
#####[A9] Dowels
The dowels are used for stacking base stations. Using the laser cutter ensures each dowel has smooch sides and is the same length.
#####[A10] Light Pipes
This piece of acrylic is used to easily see the status LEDs on each blade. It is also used to protect the top of each blade from unwanted contact or debris.
###Component Outlines
These layers are not for cutting. They are included to visually show the location of the main hardware components on the base station.
#####[B1] Outline - Power Supply
This shows where the PSU will be mounted.
#####[B2] Outline - Individual Blades
This shows a detailed outline of all 10 Blades and their components.
#####[B3] Outline - Programming Connections
This is a simplified outline of the Blade PCBs and the Bus Pirate programmer.
###Component Outlines
These layers are not for cutting. They are included to visually show the location of the main hardware components on the base station.
#####[C1] Glue Paths on [A1] / [A2]
This shows simple glue path locations in orange for the bases. Notice there are no overlaps with the mounting holes.
#####[C2] - Glue Paths on [A6]
This shows simple glue path locations in orange for the supports.
#####[C3] - Screws on [A3]
This color codes the screw locations in relation to the top base layer. Look for components in the Bill of Materials section.
Note: the purple screw holes are not cut in the top base layer [A3] for a cleaner look. They are only in the stack legs [A8] and bottom 2 base layers [A1], [A2].
- Red: Use [Z1] for PCB mounting
- Green: Use [Z4], [Z5], [Z6] for PSU and power plug mounting
- Blue: Use [Z3] for support structure mounting
- Purple: Use [Z2] for mounting the stack legs from the botton
##Construction
Please note: Follow all manufacturer guidelines for each tool and material used. Also use common sense. We will not be held liable for any damages to equipment or injuries to personnel.
***For all mentions of sheet wood cutting, laser cutting, and wood gluing, refer to their corresponding sections for more detail. This will keep the guide looking cleaner by not repeating general information.
###Guidelines ####Sheet Wood Cutting
The easiest way to cut the 2x4 foot sheets of wood is to have a store employee use the power tools. Make sure to account for the width of the saw blade as the base station layers are almost exactly 1x2 feet in size. Depending on your laser, this may cut too close to the stand offs and damage them or there won’t be enough material on the sides. For the base layers, we ensured an extra 1/4 inch of width and length to give us enough room to safely laser cut the material.
####Laser Cutting
Keep your lens clean! Make sure the HEPA filter and air assist are turned on.
How often you should be inspecting and cleaning the lens depends on the material you are using and how much cutting is taking place. As a general rule to get you started: inspect the lens after completing all the base layers, after each acrylic layer, and after one or two support layers, depending on how much the material smokes.
If the wood layers happen to be warped, use tape to hold down the edges while cutting. Also, do not cut each layer such that the warped sections protrude the same direction each time. This will cause the whole base station to warp in that same direction. By alternating which way the layers warp, the base station will straighten out once glued and assembled.
####Wood Glue Application
For any type of wood glue, follow the specific manufacturer instructions. This concerns the amount of glue, changing application methods, or longer/shorter clamp times.
Generally, apply wood glue liberally to the top of the wood surface. Avoid covering the screw holes and stack locations. Follow directions on glue for press time. We used several clamps on all the edges and placed weights on the center of the wood for at least 24 hours before any mounting. If any excess glue seeps out on the edges, be sure to wipe it off with a damp cloth.
###Step 1: Materials
Gather all the necessary materials in the Base Station’s BOM. The BOM lists quantities for a single base station.
Depending on how many base stations are being built, it may be beneficial to purchase components in bulk.
####1.1
Cut down sheets of wood such that they fit inside your laser cutter or other routing machine.
The base layers are approximately 1x2 feet. The acrylic and support layers are approximately 10x20 inches.
###Step 2: Laser Cutting
####2.1: Wood Laser cut all three base layers ([A1], [A2], [A3]).
Laser cut all three support layers ([A6], [A7], [A8]).
Laser cut the stack legs ([A9]).
Use appropriate laser settings for quarter inch wood.
Note: When laser cutting, it’s easier to group the same materials together to avoid changing settings several times.
####2.2: Acrylic
Use appropriate laser settings for sixteenth inch acrylic.
Laser cut acrylic PCB spacer ([A4]).
####2.3: Acrylic
Use appropriate laser settings for eighth inch acrylic.
Laser cut acrylic Hirose connector spacer ([A5]).
Note: If eighth inch is not available, 2 layers of sixteenth will work.
####2.4: Extras
Laser cut extras if needed: stack legs dowels light pipe
###Step 3: Gluing
####3.1: Glue the Base Layers
First glue [A2] onto [A1].
Next, glue [A3] onto [A2].
I found that only applying glue on the top side of the bottom layer you’re gluing works fine assuming clamping is sufficient.
Use [Z7] to line up the layers when gluing. The best way to do is to place at least 4 wire brads into the mounting holes of the upper layer you’re gluing. Once you apply glue to the bottom layer, dropping the upper layer is easily done by aligning the wire brads.
View Figure --- for sample alignment locations (red circles).
View Figure --- for a sample glue pattern (yellow lines).
Make sure to wipe excess glue from the edges while it’s wet.
####3.2: Glue the Support Layers
First glue [A7] onto [A6].
Next, glue [A8] onto [A7].
Use [Z7] to line up the layers when gluing. The best way to do is to place at least 4 wire brads into the mounting holes of the upper layer you’re gluing. Once you apply glue to the bottom layer, dropping the upper layer is easily done by aligning the wire brads.
View Figure --- for sample alignment locations (red circles).
View Figure --- for a sample glue pattern (yellow lines).
Make sure to wipe excess glue from the edges while it’s wet, especially in between the mote supports.
####3.3: Glue Stack Legs
As with the previous layers, use the wire brads to align each layer you are gluing. Since these pieces are small, it’s easier to use a brush to apply the glue.
###Step 4: Mount Stack legs
###4.1
Make sure your base and stack legs have been clamped for the appropriate amount of time and the glue is dry.
Flip the base over so the bottom is facing up. Use 2 wood screws [Z2] per stack leg to mount them onto the base. A total of 6 stack legs and 12 wood screws should be used.
The wire brads can be used here as well to help align the stack legs.
###4.2 (only for multiple base stations)
Glue the dowels into the stack legs.
###Step 5: PCB mounting
####5.1
Remove any tabs on the PCBs if they were used to hold a large panel together.
Connect each Blade using their 8-pin interconnects and place onto the wooden base [A3].
####5.2
Slide the acrylic PCB spacer [A4] between the PCBs.
####5.3
Place the acrylic Hirose spacer onto the PCBs. This task may be difficult if the Hirose connectors or PCB interconnects are not soldered straight. This will let you know if there is any rework that needs to be done.
The PCBs will most likely shift around the interconnect area to accommodate this spacer. This is essential for the mounting holes and the support structure to fit properly.
####5.4
Next, once the spacers are in place and the PCB mount holes are directly over the pre-drilled holes in the base [A3], use 30 small wood screws [Z1] to mount the all 10 Blades (3 screws per Blade).
View Figure --- for mount locations.
This should be done with the acrylic spacers in place to keep everything aligned.
There is enough clearance from the PCB such that the screws will not interfere with components.
####5.6
Glue these into the bottom of the base station. To ensure they are aligned properly, stack the base station onto another one and allow to dry using weight on top of the base station.
###Step 6: Power Component Mounting
####6.1
Take the AC connector and bend the pins back such that it sits flat on the base station.
See Figure ---.
Next, solder about 3-4 inches of 18-20 gauge wire onto each lead.
####6.2
Align the PSU and AC connector with the proper mounting holes as seen in Figure ---.
Use the screws [Z4], nuts [Z5], and washers [Z6] for mounting.
Screws should go top down with washers on both sides. The stack legs will provide enough clearance from the ground for the screw.
####6.3
Connect the wires from the AC connector to the PSU, trimming the length as necessary.
####6.4
Add DC power cables from the PSU to the first Blade.
For a full base station (100 motes) the current draw will be between 10-12 Amps. Make sure the wire can handle this load. We used 12 gauge wire.
###Step 7: Testing
Before mounting the wooden support layer, test the PCBs to make sure everything is working. Although the PCBs should have been individually tested during manufacturing, things can break.
Things to double check:
power / ground
signals
continuity
resistance
###Step 8: Support Structure
Mount the support structure onto the base, over the PCBs using the drywall screws [Z3]. A total of 16 screws should be used. See Figure --- for mount locations.
An easier way to align the support instead of using wire brads is to use motes that are already assembled in the cases. Since the goal is to align for the motes, plugging in several motes will correctly align everything for mounting.
Fin.
##Bill of Materials (1x Base Station):
###Wood
For the laser cutter, light colored wood will cut cleaner, leave less charring, and smoke less.
Birch Project Panel Plywood - used for the base station layers
1/4 in. x 2 ft. x 4 ft. (x2)
Refer to the Sheet Wood Cutting Guidelines for proper sizes when cutting.
Dowels - used for stacking multiple base stations
1/2 in. x 48 in. (x1)
###Acrylic
1/16 in. x 1 ft. x 2 ft. (x1) - used as PCB spacer
1/8 in. x 1 ft. x 2 ft. (x1) - used to align Blade PCBs and Hirose connectors
###Hardware
Wood Screws - used to mount Blades onto wood base
[Z1] #4 x 1/2 in. Flat Head Phillips (x30)
Wood Screws - used to mount stack legs onto wood base
[Z2] #6 x 1 in. Flat Head Phillips (x12)
Drywall Screws - used to mount wooded support onto wood base
[Z3] 1-1/4 x 8 GA Coarse Thread (x16)
Power Mounting - used for mounting the PSU and AC connector onto wood base
Switch Plate Screws:
[Z4] #6-32 x 1 in. (x4)
Machine Screw Nuts:
[Z5] #6-32 (x4)
Flat Washers:
[Z6] #6 (x8)
Wire Brads (or something similar) - used for alignment during wood glue process
[Z7] #17 x 1 in. (x8)
###Glue Titebond Original Wood Glue (Although any generic wood glue should work)
###Other
Trim Tray - used for diluting wood glue (if necessary)
Small Paint Brushes - used for applying glue, mainly on dowels and stack legs
Rags - used to wipe off excess glue
##Laser Cutter Information
###Epilog Mini 24 Laser System:
- 60w
- Auto Focus (on)
- Air Assist (on, 30 PSI)
##Laser Cutter Settings
Note: These may differ based on the laser you are using.
####1/4 in. wood (light color)
- speed: 30-34%
- power: 100%
- frequency: 500Hz
####1/8 in. acrylic (clear)
- speed: 20%
- power: 100%
- frequency: 5000Hz
####1/16 in. acrylic (clear)
- speed: 35%
- power: 40%
- frequency: 5000Hz
##Errata
The space from B2 to B3 was accidentally not adjusted like the others. Therefore the base station accounts for that. If there is another revision, both the PCB design and base station will fix this issue.