The year was 1990 and I was but a small nerdy child, overly obsessed with video games. When a game came onto the scene which was to lodge itself in my sub-conscious for the rest of my days.
A cyberpunk inspired, classic D&D dungeon crawler, you played the part of an unfortunate protagonist stranded on a decaying space station with nothing but a briefcase computer which enabled you to remotely control four droids in an attempt to enact your rescue.
Suffice to say, that game had a massive influence on me, from my love of mobile computing to the huge drain on funds my obsession with RC and FPV causes. So when a friend of mine gave me a 15" monitor which runs on 12v with the all to common phrase "I'm sure you'll find a use for it" it was only a matter of time before I placed it on a shelf beside an empty briefcase. at that point it was out of my hands, I just had to make it.... So let's get started...
Step 1: Dismantle the Monitor
I have opened up many a monitor in the past to repair them, so I wasn't at all surprised with what I found.
Along with the screen module itself, there was a power inverter for the back-light, a control board and a small board with the VGA and power sockets.
I removed everything that wasn't necessary, especially anything metal that would add to the weight of the final machine, and lay everything out for measuring.
Step 2: Cut Bezel for the Monitor
I took the inside measurement from the lid of the briefcase and cut a piece of 8mm MDF to match.
There is a little play in the frame of the lid so my plan was to simply push-fit the MDF in place and only secure it further if needed. You'll see later on that after a few issues nothing further was needed to secure it in the frame.
I rounded the corners off on the disc sander and centered the screen on the board to measure a hole to fit the screen.
I cut that out with a coping saw as I couldn't find my jigsaw... My advice here would be to look harder for a jigsaw ;)
Step 3: Mount the Screen
I measured the mounting holes on the side of the screen and 3d printed some mounts and using M3 bolts mounted the screen behind the bezel.
Then using hot-glue I attached the control boards and inverter to the back of the screen. I used masking tape underneath any bare connections to ensure there was no shorts on the metallic backing of the screen.
Fail in 5... 4... 3... 2... 1...
Step 4: Re-Mount the Screen Because You Screwed It Up!
As you can see in the picture, there just wasn't enough room behind the bezel for both the screen and the control boards. You can just make out the capacitors touching in the image.
Easily fixed, I simply mounted the screen on the outside of the bezel.
I was annoyed to begin with but the bare metal rim of the screen does look kind of cool in the end.
Step 5: Mount the Keyboard
I'm using a Logitech wireless keyboard and trackpad for this project so my idea here was to section off a tray for the keyboard to sit and still allow it to be removable.
Once sectioned off, I covered the area with black felt material and set the keyboard in place.
I intend to cover all the MDF in this material as frankly, it looks awesome :)
Step 6: Install the DC Jack
There are 2 holes either side of the case which were intended to be used to attach a strap. All that was needed was to widen one of them a little and insert a 2.1mm DC Jack Socket.
Step 7: Install Buttons for the Screen Functions
I wasn't originally intending on adding these but the screen won't automatically turn on so I needed access to the power button. I measured the distance of the buttons and glued the board behind the MDF.
I then printed some buttons and a cover and glued small lengths of printer filament onto the buttons. This will poke through the MDFand contact the buttons behind.
All that was needed was for me to trim the filament accordingly so as to be long enough but not too long.
Step 8: Cut the Main Cover and Install the Speakers
Following the same procedure as with the screen, I cut a piece of MDF as a main cover and cut holes for power button and the speakers.
The speakers are 3w speakers that will be attached to an Adafruit Speaker Bonnet (bonnet because apparently it isn't big enough to be called a hat?!?) This will handle the audio connecting directly to the GPIO pins on the Raspberry Pi.
I will also be making some 3d printed speaker grills.
Step 9: Install the Battery and Usb Hub
I cut some more holes in the MDF cover and 3d printed some "bays" for the battery and usb hub and glued them in place.
Step 10: Connect and Test the Electronics
So, here's the fun bit...
The raspberry pi connects to the screen via a HDMI>VGA adapter.
The Speaker Bonnet is connected directly to the GPIO pins.
Next we have a UPS Hat. This is exactly as it sounds, an uninterruptible power supply with its own 2500mah 1 cell lipo battery.
This enables me to hot-swap battery's or switch to mains power seamlessly without shutting down the pi. Unfortunately there wasn't enough space for the UPS hat to actually sit on the GPIO pins as it is designed so a quick look at the schematics told me that it only needed 4 of the pins so I manually connected them with jumper wires.
Power is distributed like this:
The 12V input from either the DC jack or Battery is connected directly to the screen and also to a "buck" converter which drops the voltage to slightly over 5v. This 5 volt line goes to the UPS hat and to the USB hub (the reason for this is I do a lot of work with RGB led strips which draw a lot of current and I didn't want to draw that current through the pi, this way it comes directly from the supply).
I plugged everything in and it all seemed to work :)
Step 11: Glue Everything in Place and Make It Look Pretty
Using hot-glue I secured all the boards and cables, making sure to allow enough slack on the cables going to the screen to allow for opening and closing the case.
Then I covered the remaining MDF in black felt and put everything together.
Step 12: A Warning on Lipo Batterys...
You may notice I am using a standard RC lipo battery to power this machine. Ordinarily this would be an very bad idea! Lipo battery's are temperamental at best and prove to be a fire/explosion risk when both under and over charging.
Over charging isn't an issue in this case as I will be disconnecting the battery completely when running on mains power and will only charge it in the proper balance charger as I would any RC lipo.
Under charge however would be an issue. However the battery I am using is specially made, by Turnigy, to be used in RC Transmitters and as such has a low voltage cut off circuit built in, making it ideal for this purpose.
Step 13: Testing and Conclusion...
Once everything was finished I fired it up and setup Raspbian.
after everything was configured I thought I'd do some stress testing and see how long the battery would last etc. so with a freshly charged lipo, I booted the system, turned the screen to it's full brightness and left it playing a YouTube playlist until the screen turned off (the pi was still powered in the background by the UPS hat).
Give or take a minute or two to allow for me not paying attention, the battery lasted 1hr 20m before the low voltage cut off kicked in and the screen went dark.
I have to admit, I am very pleased with that!! It makes it more than feasible to use with one or two battery's.
Being functional and certainly looking the part, I can't wait to get using it in the field!