[WIP] PROJECT BARTOP called MinPItel with 1984 Minitel 9 NFZ-300

[YaYa]

PROJECT BARTOP Minitel called MinPItel

I'm beginning a new project to build a bartop with an old (1984) Minitel 9 NFZ-300.
For those wondering what is a minitel, take a look at the english wiki https://en.wikipedia.org/wiki/Minitel

The minitel i am using is the first version even if it's called Minitel 9 lol.

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Picture taken from the french computer museum (http://www.museeinformatique.fr/)


What will be inside...
Battery

• 12x18650@3400mAh battery (total 40.8Ah !!!)

• battery management system

AC/DC Power

• 12V ups module for uninterrupted power with seamless switching from AC to DC, ability to charge while playing @6A

• 12V to 5V buck module

• 12V 10A power supply

Video

• 9.7" LCD screen HDMI used @12V 4:3/1024*768

• HDMI splitter for TV output if needed

• hardware scanline generator

Sound

• 2.1 amplifier with 3" subwoofer, 2x2" full range speakers, 2x1" tweeter

• audio crossover filter for left and right sound outputs to direct the correct frequencies to tweeter and medium speaker

• jack output with speakers sound off if plugged

Computer

• raspberry 3 (with cooling and overclocking)

• custom safe shutdown, reset board

• custom board with a relay to cut power after safe shutdown from the Pi with CR2032 battery to wake up

Controls

• arcade joystick with 6 arcade buttons

Other

• power plug, ethernet port, SD card slot, USB port, HDMI port, sound jack on the rear

The project aim is to not touch the external case in anyway to preserves the original retro look...


The cherry on the cake, i will build a second unit without computer but with full same specs. The second unit will act as a slave and will allow two players to play together

• video will be in from hdmi through master's hdmi out

• controls will be made with arduino or atmega don't know yet and will act as a USB HID to the master's RPI3

• the sound will come in from master's sound out (jack to jack)

Ultimately, i will transform the slave to be able also to act as a standalone unit (but not master) so two players can play together or each will play its own game


What's done so far...

• finding parts (no buying yet, i want to finish the GBZ before) almost done

• 3D designing of internal structure (still WIP)

• design of the safe shutdown board (the components have been ordered to make tests with breadboard before sending the gerbers files to factory)

• i bought two minitel, this part took a lot of time as people are trying to make a huge profit on those units because they are called "vintage"... I found one unit at 32€ including shipping, and another one at 28€ including shipping, while on ebay, they are sold at around 100€ or more (example of prices https://goo.gl/fSXDMh), and on other second hand sales websites around 70€
  Unfortunatly, one unit came damaged during shipping, but it can be repaired

The internal structure

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The battery stage is ok with all the ventilation holes, but i still need to work the power and computer stages.

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On the right side of the battery, you can see the BMS.
The second stage (with red components) is dedicated to the power (AC/DC power supply, 12V/5V buck, UPS module)
The third stage is dedicated to the PI, the HDMI splitter (in green), and the power amp and sound filters (sound components are in purple)

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There is still a lot of work to do with the structure as i want to add feets to PCB directly to the print but for this, i will need to have the components in my hand to make sure of screw placement (not all the sellers on ali give the schematics of their board)

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The ultimate stage is supporting the speakers (still need to add the subwoofer and rework the ventilation holes)

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Global schematics (don't pay attention to the modules i have used, they are not the right one as Fritzing does not have what suits my needs) This schema is for reference only and understanding the internals.


The safe shutdown board

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The circuitry is taken from here https://www.pi-supply.com/make/adding-a ... pberry-pi/ thanks to them for sharing their knowledge. I'm using THT only because i'm not a super expert at soldering (even if i'm not a beginner)


What must be done

• find a good solution to catch the shutdown signal from PI and control a relay to completely cut power to all components. The relay must be attached to a CR2032 battery to be able to wake up the device because if i shut down the unit and unplug the AC cord, there will be no power to change the relay state.

• design the relay board and test it

• finish the 3D design of the structure (ventilation holes, assembly holes, PCB feets etc.)

• choose a solution for the slave controls to act like a USB HID (Arduino ? ATMega ? other ?)

• design the bezel for the screen (the front of the case is round as the original screen was a CRT screen but the LCD is completely flat lol

• start trying to bend acrylic glass on the original CRT screen to give the unit this original domed style after assembly. The fake screen will be placed in front of the LCD, between the case and the bezel

• design the graphics for decoration (both units will be prepared for spray can painting or airburshing)

• ... and so many more

The final device should look like this (finished project from someone on the net)

but this project uses a 8" screen while the original CRT screen is 10" so the bezel is huge and you loose a lot of display space

The cost estimation is 600€ for master and 500€ for slave

[YaYa]

UPDATE 10/09/2017

Screen BEZEL ready, this will need professional printer as the size is approximately 21cmx16cm.
I hope this will fit, i really need to make a test print

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The most top stage is ready to go : Speakers support.
The embossed area is for tweeters, the small hole for a 40x40x10mm fan to extract heat, and the 2 others are for the medium speakers.
Unfortunately, i have no room available for the subwoofer so i need to find another room for it.
I found on ali express an extra small bass subwoofer (15mm thickness) so maybe i can put it under the battery tray.
I will see otherwise, it will be a stereo system with 2 ways.

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The first stage is complete : Battery Tray
The batteries will be packed with a heat shrink plastic and will be maintained by the pillars and the upper stage that sit on the bevel on each pillars.
On the left side, the battery management system (BMS)

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[YaYa]

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[YaYa]

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[YaYa]

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[moosepr]

Looks like an impressive project! How are you planning on wiring up all those batteries?

[YaYa]

Looks like an impressive project! How are you planning on wiring up all those batteries?

Thanks, yeah it's an ambitious project with plenty of traps to avoid lol

I am harvesting parts from broken stuffs to make a DIY spot welder machine
and i will make a 1S12P battery pack with heat shrink wrap (you know the blue stuff we can see on every pack)
The batteries themselves will be brand new, i don't want to get annoyed with sick or dead batteries, i want to charge them one by one, test and wire them all together...

I will use nickel battery plates to link the batteries all together.

The Battery Management System will lay out of the pack.

[moosepr]

There is always the debate with 1S packs as to if you need to have a battery management system monitoring each cell. I have never actually managed to find one!

[YaYa]

You don't need to monitor each cell, as parallel wiring make one enormous cell. You just need to manage under voltage, over charge, and current limiting to preserve battery life and risk of fire/burn/explosion...

Batteries in series need monitoring individually for each cell

EDIT : you can dig as deep as you want over the net, i don't think you can find a BMS that has the ability to monitor individual cells in 1S packs... You will find for above 2S, but not for 1S. For 1S BMS, you have only the IN/OUT for main circuit

[moosepr]

Yeah, I personally am in the camp of not needing a BMS on parallel cells.

I think the worry comes from the possibility of having cells that may charge faster than the others. So while the overall pack voltage may be at a safe point, there may be one cell that is potentially already full, and will still be getting the power.