ARK Vault: the Ammo-Can Library Computer

How long it runs: a full battery runs the Pi for about 30–40 hours of use: a long day of use every day for a week (rule of thumb).

Checking the battery: hold the meter button. About 13.3 V is full, 13.0 V half, and 12.0 V nearly empty: charge it then (rule of thumb).

From the wall: with the lid open, plug the wall charger in (set to lithium). About 10 hours from empty. Unplug it when the Full light comes on.

From the sun (after an event):

1. Set the controller up once in the VictronConnect phone app (battery type LiFePO4, charge current about 10 A). The BlueSolar needs a Victron VE.Direct Bluetooth dongle or USB cable to talk to the app.
2. Wire the battery first, in 12 AWG: BATT+ → battery + through the 20 A fuse (the fuse close to the battery), BATT− → battery −.
3. Then the panel: PV+ and PV−, with the panel's own leads.
4. When done, unplug the panel first, then the battery, and store the panel outside with nothing plugged in.

A 100 W panel fills it in about a sunny day. More in Off-Grid Power.

The phone: charge it from any phone charger, or from the Pi's USB port while it runs. Keep it about half charged in storage.

⚠️ Never charge with the lid shut, never run a cable through a hole in the can, and never connect the panel straight to the battery.

Anyone on the Vault's Wi-Fi can print a guide section, an AI answer or a book page on the little receipt printer. It uses heat-sensitive paper: no ink to run out.

• 🖨️ Print is at the top of every guide and page, and under each AI answer (🖨️ Print this answer). Every book has a 🖨️ button too.
• Pick a size: Tiny fits the most on the paper; Small or Medium are easier to read; Large for weak eyes. The preview shows how much paper it will take.
• Book pages: print the words (re-flowed to fit, least paper) or a picture of the page (for drawings and tables). A picture can be printed bigger, in strips you tape together; each strip is labelled (A1, A2, B1…) so you know where it goes.
• Doses and measurements: in Tiny, check every number, or print in Small.

Paper: 57 × 30 mm thermal rolls (2¼ in wide). If the paper comes out blank, the roll is in upside down. Prints fade in heat and sun, so copy anything important in pencil. Keep spare rolls cool and dark.

A mesh radio sends short text messages and positions from one radio to another, with no cell service and no internet. Every radio in range passes messages along. It needs no license. The software is Meshtastic, which is free.

• One radio stays with the Vault, under the lid. The Vault powers it whenever the switch is on.
• The pocket radio (the card) goes with whoever leaves, along with the second phone.
• Each radio talks to its own phone by Bluetooth, through the Meshtastic app. You type and read messages in the app, which also works away from the Vault.
• Or use no app at all. The Vault reads its own radio down the USB cable, so any phone on the Vault's Wi-Fi gets More → Mesh messages and a People layer on the map, with no app and no pairing. See the Vault's own mesh pages — and note the three settings there that decide whether the map is any use.

⚠️ Antenna first, every time. Screw the antenna on before you flip the switch. A radio that sends with no antenna can burn itself out.

Do these now, while there is internet:

1. Put the Meshtastic app on both phones.
2. Check each radio has Meshtastic on it and set its region to US (the app asks). The pocket card comes with it. The Vault's board may need it put on first, from a computer, at flasher.meshtastic.org.
3. Pair each radio with its phone, give both radios the same channel, and send a test message each way.

How far it reaches (rule of thumb): through thick forest or hills, ¼ to 1 mile; around town, 1 to 3 miles; with a clear view across a valley, 5 miles or more. A ridge in between often blocks it. Height helps most: after an event, raise the Vault's antenna as high as you can.

Stored, everything is inside the sealed can: the radio, its antenna (unscrewed), the pocket radio and both phones. Nothing goes through the can's wall.

Setting the radios up, private channels, range, relays and a neighborhood mesh: the Mesh radio guide. The project's own manual and the Android app are on the library drive, in Comms-Signals\Mesh-Radio.

The crank radio listens. The mesh radio sends text. A handheld two-way radio — a Baofeng UV-5R or anything that size — is the only thing in the can that lets you talk, and be answered, by anyone within line of sight. It also picks up the NOAA weather channels and the local fire and sheriff traffic.

Why it lives in the can: a handheld has no shielding of its own, and the sealed, foil-taped can is the best shield you own. A spare that still works afterwards is worth more than one that doesn't.

Where it goes: standing on the floor against the front wall, under the overhanging half of the wall charger, between the phone at the hinge end and the solar controller. That is the only spot in a packed can with the 113 mm of clear height a handheld needs, and it props up the half of the charger that otherwise hangs over nothing. Lift the charger to get it out.

• The antenna screws off and stands loose in the front corner of the latch end, beside the mesh aerial. It will not fit any other way.
• Take the battery out and lay it beside the radio, charged to about half. A lithium pack left full, in the radio, for years comes out flat or puffed.
• Program it before it goes in. The channel list is typed on a computer with a programming cable, and after an event you may have neither. A radio in the can with empty memories is almost no use to whoever opens it. Write the channel list on a card and put that in beside it.

⚠️ Antenna on before you transmit, the same rule as the mesh radio. And key the microphone only when the law allows it — see the law, plainly.

If the battery pack is dead and no charger works: a 6 × AA case sold for these radios clips on where the pack went. See running it on AA cells.

Buttons, menus, channels and the programming cable: the Using a Radio guide.

1. Switch off, unplug the chargers, and put the phone back. Mesh radio fitted? Unscrew its antenna and stand it back in its corner, and put the pocket radio and second phone back.
2. Charge the battery to about half for storage, and top it up every few months.
3. Close and latch the lid, then run one band of foil tape right round the can over the bare strips (about 1 m), over the hinge and the latch, overlapping at the end. Press it down well (why seams matter).
4. Test the seal: tape a phone inside and call it. If it doesn't ring, the seal is good. (More in the EMP guide.)

Store it somewhere cool and dry, not in a hot car or shed.

• Check the battery with the meter button, and top it and the phone up to about half. The second phone and the pocket mesh radio too, if you have them.
• Switch on and run the test. Then switch off and re-tape the seam.
• Update the library: run the installer on the library drive again, then finish the Pi's card again (see The steps).
• Replace the foil tape if it's torn or loose.

"Power too weak", or the AI takes minutes

The Pi isn't getting a full 5 volts. It can then slow itself down to about a third of its speed, and the AI suffers most: an answer can take 10 minutes instead of one or two. Weak power can also make the Pi or its drive misbehave, so fix it even if the AI seems fine.

Quick test: switch off, unplug the Pi's power plugs from pins 2 and 14, and run the Pi from an official Raspberry Pi USB-C power supply instead (never both at once). If the warning goes away, the can's power wiring is the problem.

To see what the Pi is doing, open More → Vault system status on the phone, while the AI is answering. It shows the power, the temperature and how fast the processor is running.

1. Check the battery: hold the meter button. Under about 12.5 V, charge it.
2. Check the converter: ask the AI a question, and while it's working, touch a multimeter to the converter's two output screws. It should read 5.1 to 5.25 V. Lower than that? If the converter has a small adjusting screw, turn it up to about 5.2 V; if not, replace it.
3. Check the wires to the Pi: if the converter reads fine, the power is lost on the way to the Pi. The usual weak spot is the two little plugs on pins 2 and 14 and the joints to them: the 18 AWG must be soldered to the jumper leads' short wires, not crimped into the plugs (see Wiring). Redo any joint that wiggles, and keep the wires as short as the route allows.
4. Switch off and on again so the old warning clears, and ask the same question. A healthy Pi should start writing within a minute or two.

Inside the can:

• the Raspberry Pi stuck under the lid, with the library drive (a small thumb drive) plugged in
• the battery
• the wall charger, and a solar charge controller stored for later (not wired)
• a printed stand (the riser) holding the printer, the power switch and the battery meter
• a crank radio and an old phone, about half charged
• optional: a handheld two-way radio with its antenna screwed off, standing under the wall charger (see The handheld radio)
• optional: a mesh radio under the lid beside the Pi, for texting with no cell service, with its antenna, and a pocket mesh radio taped to a second phone, packed beside the battery (see The mesh radio)
• a card with the Wi-Fi name and password, and a spare roll of foil tape

Outside the can: the solar panel, with nothing plugged into it. Panels survive a pulse fine (Sandia, p. 39); the danger is a pulse running down the wires into whatever they're plugged into (EMP guide). So the charge controller waits inside the can, and you wire it up only after an event. Never connect a panel straight to the battery.

• Lid shut and taped: the steel can acts as a shield (a Faraday cage) and keeps an EMP out. Nothing is switched on.
• Lid open, switch on: the Pi starts in 2–3 minutes and makes its own Wi-Fi. Phones join it and use the library. An EMP lasts only seconds, and solar storms come with hours of warning, so having it open is fine the rest of the time.
• Why not run it sealed? It would overheat, phones couldn't reach it, and any wire or hole through the can ruins the shield (right and wrong ways through a shield).
• The power switch just cuts the power. That's safe because the Pi is set to read-only: it never writes anything that could be left half-done. (The catch: a setting changed on the running Pi is forgotten. See Changing a setting later.)
• The meter stays dark. Hold the little red button and it shows the battery's volts (top) and the amps being used (bottom).
• The phone is the screen. Several phones can use it at once. The AI answers one person at a time, in about a minute.

⬇️ Download the parts (ark-can-parts.zip). It has every measurement and the wiring in one file (READ-ME-FIRST.txt), and the whole Vault to scale as a Rhino file (ARK-Vault-assembly.3dm).

• printed/: four parts to 3D-print in ABS, no supports, 3 walls (0.4 mm nozzle):

  • the printer riser: a stand that holds the printer, switch and meter, and the converter on the inside of its leg (two M2.5 inserts)
  • the wall cleat: a small strip the riser hooks onto
  • the Pi's base: a thin plate that sticks under the lid, with four posts (two take M2.5 inserts, two take long screws from underneath)
  • the mesh radio's base (only if you add the mesh radio): a thin plate with two rails and a tab for the antenna's socket (two M3 inserts). It also sticks under the lid

  The parts as they print.

• laser/: the ARK Vault logo, and bare-metal strips around the lid seam for the foil tape. No laser? Scrape the paint off the same strips by hand.

The long sides (both the same).

The ends: one band of tape goes right round the can, over the hinge and the latch.

1. Bare metal around the seam: etch or scrape the paint off a strip on the lid's edge and one on the body just below it, all the way round (see the pictures above). The foil tape sticks here, metal to metal.
2. Cover every bare wire end and bolt (rubber boots, heat-shrink or tape) so nothing metal touches the can.

The screws go into brass heat-set inserts, melted into the printed parts with a soldering iron, so they can go in and out many times. Every insert hole has a small bevel at its mouth to start the insert straight.

1. Heat the iron to about 230 °C (ABS). A pointed or conical tip works; an insert tip is better.
2. Set the insert on the hole's bevel, small end down, standing straight.
3. Rest the iron's tip in the insert and let it sink in under its own weight with light pressure. Keep it straight. Stop when it is flush with the surface.
4. Lift the iron away and, while the plastic is still soft, press the insert flat with something cool and flat (the side of a screwdriver). Let it cool for a minute.

Stand it at the latch end, against the back wall, terminals toward the back. Bolt on the main + and − leads and the wall charger's leads, then push the rubber boots over both terminals.

In front of the battery: stand the solar controller on its long edge, terminals toward the hinge end (stored, not wired). Lay the wall charger flat on top, with its cord coiled on top of it.

1. Snap the meter and power switch into their holes in the riser's front strip. Screw the microswitch into its slot, button up (2 × M2).
2. On the inside of the riser's leg: set the converter on the raised frame, terminals toward the front, its two ears over the two inserts. Put an M2.5 × 6 mm screw with a washer through each ear. (The ears' holes are a little bigger than the screws, so there's room to line them up.) Stick the fuse holder across the leg below it, about 1 cm up from the bottom.
3. Drop the printer into the top.
4. Stick the wall cleat inside the can's hinge-end wall, thick edge up, its top corners about 29 mm (1⅛ in) below the rim and about 6 mm from the back wall.
5. Wire it (step 7), then lower the riser into the hinge end: its leg stands beside the battery and its other end hooks onto the cleat. It lifts straight out for repairs.

The riser lifted out, with everything it holds.

1. Put the cooler's thermal pads on and set the cooler on the Pi, but leave its two little screws out: longer ones take their place. Plug its fan onto pins 4, 6 and 8 (red, black, blue).
2. Set the Pi, cooler up, on its printed base: the two posts with a hole right through go under the cooler's two screw holes (diagonal corners).
3. Turn the stack over. From the base's flat side, put an M2.5 × 8 mm screw through each of those two holes, through the Pi, into the cooler. Their heads sink into the base. Snug, not tight: these two hold the cooler on the Pi and the Pi on the base.
4. Turn it back. Put an M2.5 × 6 mm screw from the top into each of the other two posts (their inserts). If the one at the memory-card end is hard to reach under the cooler's edge, leave it out: three screws are plenty.
5. Stick the base under the lid at the hinge end, USB ports toward the front, about 13 mm in from the hinge wall and 9 mm in from the back wall.
6. Plug the library drive into a blue USB port and the printer's cable into a black one.

Under the lid: the Pi, and the mesh radio beside it.

Every part with all of its terminals, and each wire's size. Tap the picture to open it full size and zoom in. The 3D model shows where each wire runs.

Every run, with its wire. Lengths include some spare; cut to fit as you go.

• Why these sizes: everything on 12 V draws at most about 4.5 A (the Pi through the converter, plus the printer while it prints), so 16 AWG runs cool and the 7.5 A fuse protects it. The Pi's 5 V pair carries up to 3 A: 18 AWG keeps the voltage up over its length. The meter's thin wires carry almost nothing, so 22 AWG is plenty.
• Ends: ring terminals on the battery's bolts. Blue female spades on the power switch: its input terminal takes three wires (runs 2, 11 and 13), so crimp them into one spade together, or use a piggyback spade. Butt splices (crimped) or solder at the two splices. Cover every joint with heat-shrink, so nothing bare can touch the can.
• The Pi's two plugs: 18 AWG is too thick for the little pin plugs. Run the 18 AWG most of the way, and solder it to a female jumper lead's short wire about 5 cm from the Pi, with heat-shrink over each joint.
• Check your meter's own wiring sheet: some put the thick wires the other way round.
• Before plugging runs 14 and 15 onto the Pi, switch on and check them with a multimeter:

  ⚠️ It must read 5.0 to 5.25 V, with + and − the right way round. A mistake here can kill the Pi.

• Route: run the Pi's power pair and the printer cable together along the front wall to the hinge corner, and up into the lid. Leave a loop of about 6 cm (2½ in) so the lid opens freely. Tie the short wire from battery + to the fuse down, away from sharp edges.

All five wires go on the outer row. Pin 2 is the corner pin farthest from the USB ports.

Pi 5: its cooler plugs into its own fan socket instead; the power still goes on pins 2 and 14.

• The radio stands on the floor in front of the riser, and the phone stands on its end against the front wall beside it.
• If you add them: tape the pocket mesh radio to the back of the second phone, clear of the camera. The pair lies on its long edge in the slot between the solar controller and the battery, screen toward the controller (lift the wall charger to reach it). The mesh radio's antenna, folded at its joint, stands in the corner between the battery and the latch end. These are packed for storage and come out after an event.
• Keep loose metal off the can's walls (CISA, p. 45).

⚠️ This part is new and has not been built or tried yet. Check the printed base against your own board before you stick it down.

1. Leave the pin strips off the board. With pins soldered on, it won't slide into its base.
2. Slide the board into the base from its USB end, screen up, until it stops. Put an M3 × 6 mm screw into the insert in each post at the USB end: its head rests on the board's corner and holds it in.
3. The antenna's socket: push the screw-on socket of the thin lead through the hole in the tab, and tighten its nut on the outside. Clip the lead's small end onto the board's antenna end. Tuck the spare loop flat.
4. Stick the base under the lid beside the Pi, on the latch side: about 5 mm from the Pi's base, the antenna end about 10 mm in from the front wall, the USB end toward the back.
5. Plug it into the Pi: the short USB cable goes from the board to the blue USB port above the library drive. Run it along the lid between the Pi and the base, and tape the slack flat.
6. Keep the wall charger's coiled cord and plug toward the latch end, so nothing sits under the radio when the lid shuts.
7. Check the Pi can hear it, before the can is sealed: the five-minute test in the Mesh radio guide. That cable carries data, not just power, and the Vault reads the radio through it — so every phone on the Vault's Wi-Fi gets More → Mesh messages and a People layer on the map, with no app and no Bluetooth pairing. Do the test now while you can still reach the ports.

The library installer prepares the Pi's memory card, and the Pi sets itself up the first time it starts.

Two separate pieces: the Pi's card and the library drive

Outside the Vault, the library drive can also be a small SSD, or a big microSD card in a USB card reader. It just can't share the Pi's own card slot.

⚠️ Never point Raspberry Pi Imager at the library drive. It erases whatever it writes to. Check the size before you write: about 32 GB is the Pi's card; 256 GB is the library.

The steps

1. Fill the library drive with the installer kit, like any library drive: ⬇️ Download the installer kit (ark-illinois-valley-kit.zip) (see Get the whole library). Keep Offline AI and Works on every kind of device ticked. Want maps beyond the local area? With the drive still in your computer, start the library and use More → Offline & downloads → Detailed offline map (see Offline maps).
2. Write the Pi's own small card with Raspberry Pi Imager (free, from raspberrypi.com). Unplug the library drive first.
   • Device: your Pi. Operating system: Raspberry Pi OS (other) → Raspberry Pi OS Lite (64-bit). Storage: the small card.
   • When it asks about customisation, choose No.
   • When it's done, take the card out and put it back in.
3. Finish the card: start the installer again and press Finish a Raspberry Pi memory card. Pick the card (called bootfs), keep It's in the ARK ammo can ticked, and press Finish the memory card. Write down the Wi-Fi name and password it shows.
4. Put the card in the Pi and plug the library drive into a blue USB port.
5. Switch on. The green light flickers like a heartbeat while it sets itself up (5–10 minutes), then it restarts. A few minutes later its Wi-Fi appears.

It also saves PI-WIFI-CARD.html on the library drive with the Wi-Fi details. Print it and tape it inside the lid.

If the green light keeps blinking fast, it got stuck. Switch off, put the card in your computer and open ark → setup-log.txt to see why (usually the library drive wasn't plugged in). Fix it and switch on again.

Updating later, or moving to a Pi 5: run the installer on the library drive again, then finish the Pi's card again (step 3) and switch on.

Changing a setting later

The Pi forgets changes made while it runs (that's what makes switching off safe).

• To change the Wi-Fi name or password: finish the card again (step 3) with the new ones.
• Anything else needs a screen and keyboard: log in (user ark, password = the Wi-Fi password), type bash /mnt/emergency-library/OfflineLibrary/SETUP-Raspberry-Pi.sh --writable, restart, make the change, then run the same line without --writable to lock it again.

Test it

1. Flip the switch on and wait 2–3 minutes.
2. On the phone, join the Pi's Wi-Fi (Emergency-Library unless you changed it). If it says no internet, tap Stay connected.
3. In the browser (Safari on an iPhone), type http://192.168.4.1:8096. Add it to the home screen.
4. Search, open a guide, ask the AI, print something, and hold the meter button.
5. Switch off. Then do it all again with your home internet off.

• With a touchscreen (for a bigger box): use the desktop version of Raspberry Pi OS (64-bit), not Lite, and tick touchscreen when you finish the card.
• No power switch (a Pi on a shelf): untick It's in the ARK ammo can when you finish the card, and power it with a normal USB-C supply. Shut it down before unplugging: a Pi 5 has a power button; on a Pi 4, add a push button on pins 5 and 6.

A push button on pins 5 and 6 shuts a Pi 4 down safely.