sudomod

So, I've been trying to invent a Gameboy Advance build, and the shell isn't nearly as forgiving as the original Gameboy. it isn't easy to cobble together a whole bunch of components to make it work. So, I've finally decided that I need to make a PCB to get it done.

My plan is to make a PCB that can function as either a barebones common ground button PCB, or a fully functioning AIO, depending on whether you solder on the necessary components. I plan to modularize it, so you can pick and choose which components you want on the board. You can either build the onboard charger, or you can use your own Powerboost/Banggood power supply. You can use the onboard amp and/or PWM audio circuit, or you can use a USB audio board. Everything is optional: charger, audio amp, PWM circuit, type of display, safe shutdown switch, membrane vs. tactile switch buttons, etc. Either solder on the SMD components to create the various onboard circuits, or use an external board of your choice.

I'll post circuit diagrams in chunks as I go. USE THESE WITH CAUTION!!!! This is my first venture into PCB design and I'm no electrical engineer, so please pimp-slap me into reality if I post something that'll clearly burn down houses (and given that my first contribution will be the LiPo charging circuit, you'll quite likely get a chance to do this right away).

Also, I won't be selling these. I'll post the final links/files you need to get stuff fabricated, and it can be your own adventure into SMD soldering. If somebody else ultimately wants to sell populated boards, good on them. I just don't have the time or resources to do it on my own.

Links to component schematics...
- Charging circuit with load sharing & boost converter

Changelog:
Oct 13, 2017 - Initial post: Charging circuit V1.0
Oct 18, 2017 - Charging schematic updated to v1.1 with protection circuit

So, here's my first chunk of the project: the charging circuit. The goal is to use two 14500 LiPo batteries (with onboard protection circuits) in parallel [EDIT: Be very careful if doing this... See discussion below!] in the GBA's existing AA slots. Like the PowerBoost, I want to be able to use this on battery power, and also be able to plug in a power source on-the-fly to charge & play at the same time.

Oct 18, 2017 - Updated to v1.1 with protection circuit added

Here goes...


Sources:
http://ww1.microchip.com/downloads/en/D ... 51746a.pdf
http://cds.linear.com/docs/en/datasheet/3426fb.pdf
http://ww1.microchip.com/downloads/en/D ... 22005b.pdf
https://electronics.stackexchange.com/q ... 6938#36938
http://www.irf.com/product-info/datashe ... 7526d1.pdf

Interesting project ! I'm looking for a system to charge on the Fly as well

Hmm... I saw a note on Reddit claiming that you should never parallel charge Lipos that have their own on-board protection circuit. Once one battery drains and the protection circuit kicks in, excessive current flows from the higher-charged cell into the dead battery, resulting in damage.

So, maybe I should add an undercharge protection circuit to my PCB and use unprotected 14500 batteries. Or just stick to single-cell Lipo packs.

To make parallel batteries, you need to wire PLUS to PLUS, GND to GND.
You must be very careful, i insist on very careful, VERY CAREFUL with those batteries in parallel.
First charge every battery independently to full load. Test the batteries independently, the output voltage in voltmeter MUST be almost exact match, no more than 0,01 V difference !
The reason, the first plug will drain huge amount of voltage to balance from tougher to weakest. Batteries have internal resistance, and as you Know the ohm law , Voltage=ResistancexCurrent so to obtain Current you divide voltage by resistance....
Let's say you have half volt difference and internal resistance 80mohm...
0,5/0,08=6,25A !!!!!! And bow in your face... or if you are lucky, it just make wooosh and take fire...

BE WARNED...

After first plug, you charge normally as if it was a single battery.

Voila

YaYa wrote: ↑

Mon Oct 16, 2017 11:44 am

To make parallel batteries, you need to wire PLUS to PLUS, GND to GND.
You must be very careful, i insist on very careful, VERY CAREFUL with those batteries in parallel.
First charge every battery independently to full load. Test the batteries independently, the output voltage in voltmeter MUST be almost exact match, no more than 0,01 V difference !
The reason, the first plug will drain huge amount of voltage to balance from tougher to weakest. Batteries have internal resistance, and as you Know the ohm law , Voltage=ResistancexCurrent so to obtain Current you divide voltage by resistance....
Let's say you have half volt difference and internal resistance 80mohm...
0,5/0,08=6,25A !!!!!! And bow in your face... or if you are lucky, it just make wooosh and take fire...

BE WARNED...

After first plug, you charge normally as if it was a single battery.

Voila

So, theoretically, the concern about charging protected lipos in parallel isn't that much of an issue, as long as you're using identical batteries and you get their voltages synced before plugging them both in. They should both hit the undervolt limit for their protection circuits at roughly the same time, so the discharge between batteries would be negligible.

And I assume that being stored in parallel keeps the voltages synced, so therefore different degradation rates of the two batteries shouldn't really be an issue.

In the long run, fire is scary, and I see why most people just stick to single lipo packs.

yes when wired together, the individual cells become only one big battery, so the current is automatically flowing though them without notice and they get always balanced. This is not true for batteries in series, this will always needs a balanced charging but this is not our topic.
You can really go safely to parallel as long as you respect this :
- same batteries
- new batteries
- full charge before use
- test and measure voltage and if possible impedance

Wow Interesting electronics lesson ! I already have a friend that asks me to build a GBZ Advance...

Updated the charger circuit to include protection circuitry, since 14500 batteries are unprotected more often than not.

Now I just need to decide whether I want to include a USB hub on the board. Part of me wants to avoid adding a USB Hub & Arduino to conserve power, but I don't think there are enough GPIO pins to run an ILI9341, stereo PWM audio, safe shutdown switch, and GPIO button controls.

Seems like I vaguely remember that there are ways to bind multiple controls to a single GPIO. Time to do some Googling.

There are more than enough GPIO for what you want to do. I used those same needs in a mintyPi prototype and still had a few pins left over.