Introduction: Creating a Base-Station for Use With an Autonomous Vehicle.
This Base-Station was originally conceived as the control centre for FishPi's Proof-O-f-Concept Vehicle (POCV). I had in mind an aluminium flight case with a keyboard, mouse, LCD, and a USB Hub along with extensions for USB & Networking. The Base-Station would connect direcftly to the POCV via a 32-pin umbilical.
In this instructable I will demonstrate how to build your own accompanying Base-Station.
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Step 1: Parts.
Initially the Base-Station featured;
- Aluminium Flight Case (Large).
- 12" IBM LCD & Touch Screen.
- Sejin SPR-8695TU Keyboard & Trackball.
- 7-Port USB Hub.
- 32-Pin Aircraft Plug & Socket.
- 12v to 5v DC DC Converter.
- 3mm Birch Plywood.
- Bulgin USB Buccaneer.
- Bulgin Ethernet Buccaneer.
- Panel Mount USB Extension.
- DC Jack.
- Panel Mount Fuse Holder.
There are no batteries inside the Base-Station. Power is supplied from either a 12v car battery, or a 12v PSU.
Several months ago I built the LapPi, a Raspberry Pi Laptop. There are many similarities between the two. It is worth noting that although the LapPi was published first, work on the Base-Station had began well before the LapPi's completion.
Step 2: Repairs
The 12" IBM LCD I planned to use didn't work. The back-lights had failed. Before I could continue they needed to be replaced.
I shall spare you the exact details on how to do this, there are quite a few guides on Instructables detailing how to replace failed CCFL back-lights in LCDs.
In short one dismantles the LCD, removing the LCD panel from the enclosure. In larger screens it is normal for there to be two CCFL tubes, sometimes even four, but on this smaller screen there is only one.
Taking a slow and methodical approach to swapping the back-lights is the best way to tackle the repair. The CCFL tubes are delicate and rushing will only lead to accidents.
It should take around one hour to replace a single CCFL tube correctly.
Now that the LCD has been repaired we can continue with the Base-Station build.
Step 3: Nicley Framed
The LCD goes inside the flight case. Before you do any work check you have ample space for the LCD panel. Once you are happy we'll need to prepare the LCD & the case.
1 | Dismantle the LCD. Make sure not to damage any of the cables as you will need those for the LCD to work later.
2 | Strip the inside of the flight case. Take care not to damage any of the cardboard liner.
3 | Measure the upper case's internal dimensions.
4 | Cut a plywood panel using those measurements.
5 | Check that it fits inside the upper case.
The plywood board I had wasn't tall enough to completley fill the upper case so I had an open strip at the bottom. Later on I will fill the gap with a wooden strip.
6 | Using the old plastic frame from the LCD measure the viewable area (L x W).
7 | Transfer the measurements onto the plywood panel make sure the area is centred and level.
8 | Cut out the viewable area from the plywood panel.
9 | Check your work fits.
There are two sections to the screen pack. The touch panel needs to sit in front of the LCD. Both need fixing in place.
10 | While the plywood panel is face down measure the touch panel and mark where it will sit on the back of the plywood panel.
11 | Glue wooden guide strips to the back of the plywood panel. I have left approximately 1mm of clearance on each side for foam padding.
The screen rests directly against the touch panel. I have put some foam strips around the edges to give a little bit of protection.
12 | With the plywood panel face down and the touch screen in position, place the LCD face down on the back of the touch panel. Make note of where the mounting holes are for the LCD.
13 | Build up removable brackets to hold the LCD in position.
Step 4: Supporting PCBs
There are three PCBs that power & control the LCD & Touch panel; the main logic board, button board, and the inverter for the back-lights.
The boards are arranged in a specific pattern. Taking the screw holes in the boards as reference points I drew a mounting pattern onto an A4 sheet of paper.
Holes are cut into the pattern and the paper temporarily attached to the back of the upper case. Wooden blocks are permanently glued to the card liner in the upper case. Once the glue has dried the paper pattern is removed. Screw holes are drilled into the brackets and the PCBs can be test fitted.
Step 5: Wooden Blocks
The LCD plywood panel assembly must be securely held in place in the upper case.
Along the inside edges I have placed wood blocks. The blocks are secured using wood glue & screws. The wood blocks are 3mm lower than the edge of the upper case. When the plywood LCD panel is fitted the panel sits flush with the edge of the case.
The touch panel & LCD moved around too much when the touch panel was pressed so extra brackets have been added to stiffen up the assembly.
The filler strip at the bottom is permanently fixed to the blocks.
Step 6: The Other Half
The lower case is built by the same principles used to construct the upper case. Eight wooden blocks fit around the inside of the case. A made-to-measure plywood panel sits on top of the blocks, and is held down with eight large wood screws.
An opening is cut into the panel wide enough for the keyboard & trackball combo to fit inside. A box section screws to the plywood panel and runners are fitted inside. The keyboard rests against the rails so it sits flat with the plywood panel. If the keyboard were to protrude above the level of the plywood panel there is a chance it might come into contact with the LCD, causing damage to either items.
Additional openings are made for the Bulgin USB & Network Bucaneers, 32-Pin Aircraft connector, Cable-Way, and the DC Jack & Fuse holder.
A 7-Port USB has been removed from it's casing. The USB Hub is fixed inside the lower case using the methods described to mount the LCD's PCBs. When installing devices like a USB Hub it is worth remembering to allow space for any cables which will later be connected.
Before final assembly all surfaces are smoothed with fine glass paper before being sprayed with a protective satin varnish.
Secured to the back of the larger box section is the 12v to 5v DC DC Converter. The converter will provide power to the USB Hub.
The buttons on the button board are removed and wire extensions fitted. The plywood LCD panel is modified and three push-to-make buttons hot-glued in along with a power indicator LED. Notches in the lower edge of the plywood panel make space for the cables to pass between the upper case and lower case.
Final assembly of the screen pack takes place away from the workshop to help limit the incursion of dust particles.
This completes version one of the Base-Station. Connectivity to the POCV is available via the 32-Pin umbilical. Access to the POCV's HDMI, Network connectivity, and USB functions are now available. In principle.
Step 7: I Love It When a Plan Comes Together
- Sharp LQ170M1LA3 17" LCD
- LCD Controller Board, Inverter, Button Board, & Cables.
- 40 Pin IDE Cable.
- HDMI to DVI Cable.
The viewable area has been increased on the plywood panel. Larger brackets and two cross spars fix the larger panel in situ. Between the spars in an additional panel to which is mounted the PCBs.
I cut an HDMI to DVI Cable in half, counted the individual wires in the cable, 15 and added six to the count for power (3x 12v & 3x gnd). By splicing in the flat IDE cable we greatly increase the resilience towards bending. The previous three round cables kinked easily and over time this would have led to broken cables.
Step 8: Third Time Lucky
- 512mb Raspberry Pi.
- D-Link Wi-Fi Router.
- Cat5e Cable,
- SMA Female to SMA Male Panel Mount Pigtail Extension Cable.
- USB A to Mini B Cable.
Before beginning the modifications I checked to make sure all components work. Originally I had intended on using a USB Dongle but quickly upgraded to a Wi-Fi router. Both the router and Raspberry Pi are installed into the small space under the keyboard.
I installed a false bottom into the keyboard space. The Raspberry Pi rests on a foam pad (old Yoga Mat), and two wooden blocks on the underside take the screws.
The hole for the 32-Pin Aircraft connector has been blanked and a hole drilled for an RF cable extension from the router.
Power for the Raspberry Pi is drawn from the DC DC Converter and the Wi-Fi Router is fed 12v directly from the PSU via the DC Jack.
We're using the Raspbian “wheezy” image in the Base-Station, which is available from the Raspberry Pi Foundation's website.
Over the summer we'll be broadcasting live video, and or images from the POCV during testing. For loads more details about the FishPi project please visit http://fishpi.org
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