Case Design option

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• Board layer (yellow) printed in 2 parts, to hold and align the electronics.
• Screws together, boards screw in as well
• External case (blue) is printed in halves, and slid over the electronics
• 4 final screws in the 4 corners hold all together
• Exaggerated back angle, for a stable viewing angle in landscape or portrait

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Pi Case

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• See Part Library
• 155 mm Screen Length
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https://youtu.be/_5fTuE0_8hU

Pi Wiring Finalization

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No Splice needed

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Use header on Pi to feed screen with 5V

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Bat Pack

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Rip USB cable and solder 3 pins to back of Screen

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One end of USB cable cable just plugs in, other is cut - or solder to underside pi board on d-n and d-p pins (See Here)

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• External battery
• Battery USB to USB-C on Pi
• Later may make our own USB-C cable

Bat pack. Right now there will just be a hole in the back where we can plug the adapter in directly, and have an external battery pack. Something like this would be ideal if we wanted to integrate it into the shell.

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Back of Screen

Power Pins (2) on back of screen

Data (3 pin) (under pi)

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Pi on top

3A to USB C

Whatever plug is available

Plug type C - Male

USB B

Chris Work

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Working Configuration

USB B on top, HDMI to right?

(Blue wire => 5V headers + USB signal to back of Screen)

Direct soldering to underside of USB on Pi (Green Star) Find D-n and D-p (TP18=D_n TP19=D_p) pins. The Gnd is the same circuit, not really needed -JD This wiring is verified and works! See This Slide

The best battery pack I'm not sure. Right now there will just be a hole in the back where we can plug the adapter in directly, and have an external battery pack. Something like this would be ideal if we wanted to integrate it into the shell, getting one that comes with the right usb cables --

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Although I know we'd much rather move towards having our own battery packs.

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Solder Power and USB to Screen

Power Here

USB Data Here

Solder directly to board, or attach correct size dupont connector header. Pads are spaced correctly to use a dupont header.

This eliminates the need to use the side mounted USB ports.

Solder USB to Pi

• Direct soldering to underside of USB on Pi
• Find D-n and D-p (TP18=D_n TP19=D_p) pins.
• Solder leads to these pads. Use provided wires with male dupont connectors, cut one end off and solder that to Pi.

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Pi -> Screen Final Wiring

• 5v power to pin 4
• Grd to pin 6
• D_n and D_p soldered to underside of Pi

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Chris Evaluation

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USB C plug

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USB C on edge of Pi Case

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• External battery
• Interface cable goes from USB C to regular micro USB, so we can plug in any battery pack that has a USB connection?
• USB C M-F connector ?
• C female goes on edge of case so power pack can plug in there

Back of Screen

Power Pins (2)

Data (3 pin) (under pi)

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Pi on top

3.5A to USB C

Plug type C - Female

Plug type C - Male

How to solder to USB C plug: get one with a solder pad already on it

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Sliced apart some usb micro - C adaptors and tried this out, it is difficult!

PowerPack Testing -

• Pi - Wall plug = 3A
• Screen draws 700 - 730 mA (820mA at one point during boot)
• 2.1A battery powers everything up, low voltage indicator comes on
• Used only one output cord (USB A to USB C)
• Screen Draw is higher on battery pack (825 - 850 mA)
• 2.4A power pack also works, but has “Low voltage” indicator.
• Used only one output cord (USB A to USB C)
• Screen Draw is higher on battery pack (815 - 830 mA)
• Low Power Icon (main power light on Pi also goes out)
• Learned this is a low voltage alarm. Battery pack and cable combinations result in slight voltage drop
• USB cables with undersized wires result = same.

Further research online:

Stackexchange - 3.0A supply will be sufficient

Raspberrypi.org - 3.0A @5V

Stackexchange - comprehensive testing on power banks and cables

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Testing in Lynden with USB Inline Power Monitor.

• Pi + Screen total draw is 1.25 to 1.50A during boot and idle. Consistent with wall power, 2.1 amp battery pack and 2.4amp battery pack.
• *Voltage warning is occasional when running from battery packs. I only had 2 for testing, both get occasional warnings.
• ** Third party (non-pi) usb C cable to 3.1A wall outlet also gives voltage warning at boot.
• **Pi wall charger only consistent way to avoid voltage warnings.
• *Online research indicates that a short 20” or less, high quality, USB cable is likely to eliminate the low voltage warning. All testing done with 60” USB C Cable.

Reference:https://www.tomshardware.com/reviews/raspberry-pi-4-b,6193.html#power-and-heat

BOM

• 12” USB C Cable.

See for example of 3A/5V - https://www.amazon.com/10400mAh-Portable-Charger-External-Compatible/dp/B07JYYRT7T

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These cables should work:

https://www.amazon.com/Cable-Matters-USB-C-Black-Feet/dp/B07NL8CMKR?th=1

Plan B

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• Innovate Asterisk Tablet
• https://www.instructables.com/id/Raspberry-Pi-4B-3D-Printed-Tablet/
• Save this for later. Screen is easier to connect:

MVP Case Configuration and Assembly

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NewCAD for thinking thru how to print the case. Two layers

• Layer 1 (Yellow) = Bezel - print in halves or 4d.
• Layer 2(Grey) = back of case. May be able to put a fold line in (aka D3D electric panel) to get it printed in 1 piece.
• Still working thru how to best 4d print.
• 4 screws to hold Pi. Mount from underside to pylons attached to rear of case
• 4 screws at corners to pull case together.
• Add grip to rear where batteries will someday be? Possibly some sort of kick stand to hold screen upright on desk/table.
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Low Profile Wiring

MVP Case Configuration and Assembly

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CAD for thinking thru how to print the case. Thinking 3 layers in 2 halves

• Layer 1 (Blue) = Bezel - print in halves if 6” bed
• Layer 2(yellow) = mid level of case - print in halves if 6” bed
• Add handle to layer 2.
• Layer 3 (Orange) = back holder for Pi, External ports exposed. This layer can be expanded, or eliminated when external battery pack added
• Pi Screen Purple

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Low Profile Wiring

4D Printing

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Print Bed

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Perforate Bezel and bend into flat shape afterwards with heat gun. See 4D Printing example.

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3D print of bezel

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CAD for thinking thru how to print the case. Thinking 3 layers in 2 halves

• Layer 1 (Blue) = Bezel - print in halves if 6” bed
• Layer 2(yellow) = mid level of case - print in halves if 6” bed.
• Layer 3 (Orange) = back holder for Pi, External ports exposed. This layer can be expanded, or eliminated when external battery pack added
• Pi Screen Purple

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Wire Connection Requirement

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Original Cables - slanted config

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Jeremy softer USB to micro

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Also other USB ports on this side

Front of .

Screenz

hdmi

USB

Power

Not accessible as is. Can do a broken 2-wire connection to the outside. Immediately, ignore this and

Enclose this area inside case, leaving ports exposed to exterior via a inset area on rear of case. CAD File

Enclosed - Internal Wires inside.

Resolving the Cable Issues

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Issue: power cable not accessible, and it needs to be plugged in and unplugged as needed.

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Jeremy softer USB to micro

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Screen

Bat pack

Pi

Tested USB to Screen Connector at rear instead of side. This works great, touch screen works without need for USB connection at edge or screen, will greatly reduce width of bezel at screen edge. Notes in Jeremy Log

Tested Power to Screen Connector. NOTE: this powers the screen even when Pi is shutdown. Need to add a transistor circuit and a shutdown/startup script similar to this. Once power switch off, or USB C disconnected, screen powers down. Punt this to next version and use external power switch (on USB cable) for now?

Not accessible as is. Can do a broken 2-wire connection to the outside. Immediately, ignore this and. USB C diagram from pi site. Could leave an inset notch at lower rear side of case for access. See CAD Case concept. This could help protect charging plug from jostling while tablet being used upright on a surface.

Is this the only practical configuration for now?

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• Cables determine this:

Screen

hdmi

USB

Possible solder pads for power and USB on back of Display could eliminate side USB connections? Unable to find any documentation.

These may be test locations for the factory? But could serve as viable access points to these inputs without the need for bulky connectors

Screen can be powered from pins 4 and 6. Tried it today(2/1) and the screen powers up and Pi boots correctly.. See Jeremy Log

Critical Access Points to Be Aware Of

Pi:

1. Power for Pi - USB C
2. HDMI to screen - either one
3. USB B for USB Touch

Screen:

• HDMI
• Power
• USB B for USB Touch

Needs to be unpluggable: power cord

Minimum Minimum Viable Product Roadmap

Initial Implementation:

• Screen
• Pi on the back,
• Battery issue - right now with limited Texas site internet - and questions on whether our boost converter will hold a stable voltage and not fry the Pi - we don’t want to risk frying the pi

Disadvantages:

1. 2 power cables from outlet - one for screen, one for pi
1. See Here for work around.
2. Step 2
1. Add battery pack
2. Add Camera Module

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Howto:

• Multiple parts are Merged into one doc
• Before you do that, prepare files for merging
1. Make compounds from multiple parts so that move/rotate is easy
2. Eliminate sketches and other artifacts to make dumb objects. This reduces memory size
3. Save all your files in version history
• To merge, go to FIle->Merge
• Merge works only with FreeCAD files
• For merging other file formats such as STL or STEP - save them first as FreeCAD files
• Rotate and move things to make assemblies.
• Assembly workbench is not needed
• When you have the final product:
• For each individual part: select, copy to new document, save each part individually.
• Then upload the individual parts back to the Parts Library
• This will save the positionally correct individual part in its respective version history, allowing others to quickly merge the files into the same final assembly very rapidly.

Advantages of Merge Workflow:

1. Large assemblies can be worked on by unlimited numbers of people, as opposed to a single master draftsperson
2. A design file is not locked - people can upload new files as they like on any part of a project
3. This process is accessible to anyone without using advanced and expensive PLM toolchains

Disadvantages of Merge Workflow:

1. People are not used to this workflow. People are typically familiar with a process where a single draftsperson that does most of the work. This requires a collaborative mindset in which each person pays attention to making files accessible for others to build upon

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Merge Workflow + Pi Tablet

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Links:

Marcin YouTube for this Page

Wiki Page - Merge Workflow

FreeCad 101 - OSEWiki

Light Module

Pushbutton light for the tablet

The light module has a high power LED light element that is activated while a button is pressed.

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To power the light module from the battery module, the voltage is boosted and a control module limits power to the LED.

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Now, to package the pieces of the light module into an assembly, we start with the dimensions of the components:

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Button: ¼” W x ¼” L x ¼” H (with two leads extending from bottom)

Boost Converter: 13/16” W x 1 11/16” L x ½” H

LED Congtroller: ⅝” W x 1” L x ½” H

LED / Fan assembly: 1 ⅝” W x 1 ⅝” L x 1” H

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The fan on the LED assembly has a heat sink that vents warm air out two sides.

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Pi Detail

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Dimensional drawing:

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Pi

Case

Pi in Case

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Download pi with case

Screen Detail

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Dimensional drawing:

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Freecad File:

Bezel CAD for testing screen Fit. Need a way to attach the halves.

Collab and Rapid Prototyping Workflow

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Dev Principles

1. Work docs with most current page brought to the top
2. Work Log, Part Libraries, 60 second rule
3. Work Logs with most current on top
4. Scrumy with most pressing Task on top
5. Review Scrumy, Work Doc, Organizing Wiki Page on an ongoing basis
6. More details at Test-Driven Design and Second Toyota Paradox

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Rapid Prototyping

Laser Cutter

Rapid Laser Cutter Folding File Generation

FreeCAD

FreeCAD

STL

3D Printer

Scrumy

Work

Logs

Part Libraries

Working Docs

Circuit Mill

Ki

Cad

Operating System

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1. Stock Raspbian Desktop - not the full version
1. Light is non-gui - just on-off switch like a flashlight
2. Insert card, go through settings such as keyboard and time zone - and then change screen resolution to something like 1280x720 - resolution is really high here
3. Then enable keyboard - see Stack Exchange for Matchbox-keyboard

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Notes:

1. Matchbox-keyboard software is super lame, does not pop up upon text fields but you have to keep it on as an app. It disappears behind the wiki, and it shares screen with the wiki. Completely unusable from a functionality perspective.
1. Ramifications - install another keyboard software that is better?
2. Install whole new OS - Android - instead, assuming it has a good touchscreen like any android phone?
2. “Florence” seems to be a decent on-screen keyboard, resizable and stays on top well. I do wish there was a “swype” style keyboard like Android, so trying two android builds as well
3. Also amazing feature of this, we can easily have multiple operating systems on the device; pop it open and swap between SD cards to switch between Android and full Linux

Modular Breakdown - Visual

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Batteries

5v Cooling Fan

need it for processor speed otherwise clock speed slows for cooling purposes

Camera Module

Touchscreen

18650 battery charger

(from 5V supply)

Pi

Power Supply

(USB C)

10W LED

LED Driver

Boost Converter

Takes 3.7V batteries and boosts voltage to 5V for the Pi

Form Factor Ideas/Discussion

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• What dimensions are we aiming for?
• Any that work: needs to have access to touchscreen keyboard
• Limited by wiring
• Can/do we need lower profile connectors inside the case?
• Example from ebay’
• Yes, but we don’t have them so not now
• What ports do we leave accessible to exterior?
• Pi?
• Screen?
• Battery Charger?
• Audio
• Can we add “extensions to the ones needed? Then Pi board can be located elsewhere?
• What ports need to be utilized internally?
• Pi?
• Screen?
• Hdmis?
• Power
• Cooling - vents needed? Sides? Top?
• Hand Grip?
• Tripod mount at bottom or Side
• Camera in top or left/right?

Front

Display

Bottom

Right Hand Hold

Diagram this. See Next page

How do we get right hand to work touch keyboard?

Left Hand Hold

How do we hold with both hands so we can type? Screen must go all way to the edge, unless we are not using it like a phablet but more like a tablet, in which case screen location is not important.

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Can we print and wire a soft keyboard that is part of the case? Perhaps the challenge of a thumb type code suggests an external keyboard is the mode recommended for the rasp pi

Thingiverse Example:https://www.thingiverse.com/thing:1503651

Wiring Requirements

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• Based on MVP: wall power + working pi in case
• Do this by end of day Fri Jan 31, at least to a mockup rapid rapid prototype in cardboard or paper as the plastic case prints.
• Need for laser cutter for rapid RP emerges - even in thin cardboard. Should plan on this for next STEAM Camp - 4W laser. See RP Workflow next page

Pi

USB To screen

Pi USB C Power

HDMI

Screen

Form Factor Ideas/Discussion

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1. Start with wiring - we only have the cables that we already have
2. Once wiring is clear, it will determine much of the geometry for now
3. We probably end up getting custom wires to make the thing fit better, otherwise the tablet is oversized

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Part Library

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Link

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Battery Holder v0.1

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M6 Bolt holes

(USB C)

Design Rationale:

• Clamping bolts can be used for wiring
• Wiring can produce series, parallel, and hybrid configurations
• Bolts allow for stackability via wire or or busbars with the correct hole spacing
• Clamping bolts and battery orientation determine series or parallel configuration
• Protection circuit can be added
• In 3.7 volt config, requires boost to 5V to power the Pi
• In 36V configuration, is a base pack unit for vehicles and cordless welders
• Lithium ion is not eco-friendly. We can envision a future with Lithium is a scarce resource, with 30-200 years of supply left

The future of batteries?

Use chemical energy instead of electrochemical energy, for a factor of 10-100x increase in energy

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Video discussion of the future of batteries:

Advanced Battery Holder with BMS by Luke

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https://wiki.opensourceecology.org/wiki/Open_Source_Battery_Pack

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Modular Breakdown

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Case

• Case
• Battery Pack
• Screen
• Charger for batteries (should this be combined with BatPack?)
• Power supply

Screen

Cam

Bat Pack

Power Adapter

Boost Converter

Pi

Case

Interface Design

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Marcin

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Jeremy

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Don

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Jessica

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Tom

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Case

• Case
• Battery Pack
• Screen
• Charger for batteries
• Power supply
• Software
• Keyboard… printed?

Screen - has a certain bolt or mounting pattern, and particular cable arrangement, and particular dimens

Cam

Bat Pack

Power Adapter

Boost Converter

Pi

Minimum Viable Product

Minimum Minimum Viable Product - Phase 1 - 2 days

Minimum Minimum Viable Product - Phase 1 - 2 days

1. Working hardware and OS
2. All inside a case
3. Powered by batteries or wall
1. Could integrate off the shelf USB Battery bank of similar form factor to OSE battery module until OSE Battery Pack is ready for integration. Would allow 100% wireless use!
4. Camera integrated into case.

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• Working hardware and OS
• All inside a case
• Powered by batteries or wall
• Camera integrated into case.

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• Add camera
• Add batteries

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Top Level Requirement

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Detailed Requirement

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• First check is [[OSE Specifications]]
• Has tripod mount built in
• Phonebloks style modularity
• This product is designed to be modular and continuously evolving
• MJ - 36V expernal pack (10 cells) - modular add-on for extra battery life
• Standard - 5s battery pack (50Whr) - so Pi Tablet lives for 5 hours on a single charge
• 12 hr lifetime for a full day of documentation

Battery Life Calculations

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• Need 12 hours for 12hr time lapse without need to charge

Thoughts/Note for Next Iteration

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• Consider low profile cables
• Consider alternate screen with only a single connection point? Pi screen is slightly more expensive, but has a single connection for power, HDMI, and inputs. Pi Screen may change the form factor due to location of screen control board, but likely to significantly simplify hardware integration and cable routing.
• Reduced wiring issues by soldering connections to available pads on back of screen. HDMI is the only “poor” connection due to the size of the connector plugs.
• Pi screen seems much lower resolution. Big trade off to consider?