Bacteria's project - Modding a GP2x....FINISHED

[Valium]

Life of Brian - Yup, pays to be thrifty! I spent about 2.5 hours this morning looking on various sites about batteries, and updating this blog. £32.94 is not cheap (about $71.30), but at least it isn't silly money!

I am hoping I can recharge all together like this as it means I can seal them into the case in a more permanent manner. I imagine it should be ok, a while back I put a pack of 6 x AA cells in a pack and recharged them in a 9v recharger unit (same connectors) for 48 hours and they were ok; but I don't know if this is good longterm or can damage cells.

What I don't know (and hoping for answers please) is if you have 6 x 5500NiMH cells together in series, making 7.2v, that a 7.5v mains is fine, and in effect 3amps divided by 6 cells = 500mAh per cell, so to recharge 5500NiMH cells would take 11 hours from 7.5v 3amp mains power inlet (ie PSone power cable). Someone must know!!! (and if there are any longterm downsides).

I suggest buying a battery charger instead of the Psone power cord, with the power cord, the batteries can and will overcharge. You wouldn't want to go battery shopping again would you?

[bacteria]

Valium - Thanks for the reply. If I could recharge the cells in X hours, I could use a normal household timer to only allow the mains plug to work for a certain time and then cut out. Would this work? I understand under normal conditions that if a NiMH battery becomes overcharged, it "vents" off the pressure and air bubbles escape from the battery so it doesn't explode.

I am in the UK, so need the UK 3 pin plug and power supply recharger, given what I need to do, any chance you could point me in the right direction as to what I will need please??

[vskid]

What I don't know (and hoping for answers please) is if you have 6 x 5500NiMH cells together in series, making 7.2v, that a 7.5v mains is fine, and in effect 3amps divided by 6 cells = 500mAh per cell, so to recharge 5500NiMH cells would take 11 hours from 7.5v 3amp mains power inlet (ie PSone power cable). Someone must know!!! (and if there are any longterm downsides).

It will actually take about 2 hours to charge. When the 7.5v is spread across the 6 cells, they still get 3A at ~1.2v. So its the same as thinking of the pack as a whole, the number of cells doesn't really matter. You'll want to measure what the actual amperage from the PSone adapter is when you charge them, though, those ratings aren't always correct.

And while overcharging NiMH batteries won't likely burn your house down, its still not good on them.

[bacteria]

vskid - Great, thanks for that info. 2 hours, great! I will take your advice and check the amperage. I will have to be careful and only recharge for 2 hours.


Update: I was going to do the case today, but ended up playing on the PDA. I tested MAME on the PDA, it does run some old games at fullspeed however there is that wretched issue with the fact you can't press two buttons at the same time (eg move right and fire games); so am stuck with games only needing movement, like PacMan.

I had the MS game pack (Dig Dug, PacMan, Ms PacMan) they work fine and fullspeed. I have some basic NES games like Spot I like which are fine too.

I upgraded the ROM from Pocket PC 2000 to Pocket PC 2002 fine, looks pretty.

I decided I really don't need extra memory or CF expansion as the PDA can only play very limited games due to the two button press issue and the speed of the PDA; however as a PDA it is excellent. I have 31mb free to install stuff ok; I intend to Google to see what quality games I can get for this old PDA for free. It's all part of the fun! Anyway, if I want a games system I have far better options than using a PDA; although I must say, my mod holds nicely in my hand, and all the buttons work properly (except the mic button as I was never going to use it to record memos, not a useful facility).

When I put some more games on system (I like a play!) I will finish the case - tomorrow or Friday.

[bacteria]

After advice from Skyone, I searched e-bay and found a product I believe fits the requirements, and have now bought it:
eBay

[Skyone]

Skyone - Personally I like AA's because they are easy to get hold of and light; however 6 cells only seem to power the PSone screen for about 1.5 hours (unmodded PSone screen) and 2 cells (as powerful as you can get) only power the GP2x for about this; sometimes more, sometimes less. That is 8 cells; realistically, to get good life from both systems I would need 16 AA cells, 6 x 2 sets in parallel and 2 x 2 sets in parallel - the GP2x is such high drain that having 6 x 2 sets in parallel would give warm batteries and be pushing the AA's. You won't be able to run both devices from one set of 6 AA cells, I doubt the system would even work for a few minutes. The C cells I have now bought are high drain quality. Incidentally, 12 x AA cells weigh about 380g, so the 6 x C cells are only about 120g more - about the same weight as 16 AA's!

Yes, but that set-up would be extremely inefficient. Look for a buck/boost DC-DC converter on Digikey.com and TI.com that will boost ~2v up to ~8v (or adjustable). That way, you can use 2 or 3 2AA packs in parallel and power both the GP2x and the PSOne screen from the same source with minimal consumption.

Honestly I REALLY advise doing this, only 6AAs!!

[bacteria]

Very interesting; however the GP2x takes about 1900mAh (3v) and the PSone screen about 750mAh (is that right, unmodded screen?; 7.2v), so the drain is very significant. Two 2700NiMH photo grade AA batteries, quality brand, only gives 1-2 hours life after full charge in the GP2x.

Thinking about it, I don't know if I can do this, but worth trying: rig up the six C cells into three packs of two cells in parallel (3v, 16500mAh) and the same six cells also in series to power the PSone screen. That would give long life between charges for sure (several hours). Would this work well?

[Skyone]

Thinking about it, I don't know if I can do this, but worth trying: rig up the six C cells into three packs of two cells in parallel (3v, 16500mAh) and the same six cells also in series to power the PSone screen. That would give long life between charges for sure (several hours). Would this work well?

Yes, if you used the 3 * 2C with the step-up that I mentioned earlier, you'd get about 6 hours of battery life after you deduct a bit of efficiency from the boost converter. You ultimately never want to have two separate battery sources. If one source dies before the other, you're wasting a lot of power.

<img src="http://i11.tinypic.com/7xb9lb6_th">

[bacteria]

Thanks for that.

What I was meaning is it is possible to have 3 sets of 2 batteries in parallel to give 3v AND use the same 6 batteries to also give 7.2v for the screen? In that way I won't need extra components (eg step up converter)?

[Skyone]

Thanks for that.

What I was meaning is it is possible to have 3 sets of 2 batteries in parallel to give 3v AND use the same 6 batteries to also give 7.2v for the screen? In that way I won't need extra components (eg step up converter)?

Nah, you can't pull two different voltages from the same set of batteries.

[bacteria]

Skyone - can't find a reasonably priced step-up regulator in the UK, so I will have to use my 6 x C cells to power the screen and a TI board to reduce the voltage to the GP2x to 3v.

I think I have managed to secure a deal with a chap in Australia on the GP2x forum for his GP2x system for the cost of postage "and a cheap pizza" his screen is smashed, but that doesn't matter as I don't need it. This would save me using my pristine one, assuming he sends it to me. I am well known on that forum too BTW.

Anyway, the GP2x uses a digital joystick, the one supplied on the GP2x is a small one and not a very good one.

I had a hunch at a car boot sale I visited recently - I saw this plug and play tv game controller, haggled the seller to about £1 ($2) for it. The games on it are bad, however that wasn't why I really bought it.



I opened it up, and my hunch was right - the joystick on the controller has a plastic circle at the base which connects directly to the 4 contact pads (like a D-pad).







The GP2x has a quirk - you can press multiple buttons at the same time and they all register, hence when you move the joystick into a diagonal position it registers two of the four directions (ie up,down,left, right) and makes a diagonal.

Some games are best playing with a D-pad, however side-scrolling shoot-em-ups need diagonals, this joystick is ideal.

This post is applicable for this GP2x project, but as it is also I believe a good snippet for an alternative D-pad, so I am also posting this in Forum 42 as it is a good tip for general console making.

[bacteria]

These are the batteries I got - 6 in total (3 packs).



I placed out the PSone screen and mobo with the batteries in about the right position, the speakers and the D-pad joystick.



The gaps on the right will house the button controls. If I used small speakers I wouldn't save much width because my case will be flat and 29mm high (the batteries are about 25mm high), so I may as well use proper speakers and have quality sound.

Everything will be quite tight, given I need to add tact switches, TI card step-down regulator, switches, wiring, side buttons, SD card input extension, relocate the PSone contrast and volume controls.

The case will be 255mm wide (plus sides, 260mm) and 175mm in length (180mm when finished). If I used thinner batteries (less life) I could have reduced the case to 220mm wide and 155mm long; the difference isn't worth bothering about; the extra is better for longer life cells and better sound.

Now the preliminary sketch has been done, I can go about making it a final design.

[bacteria]

Ok, I have tried various combinations, ones which will be fairly evenly weighted and provide enough space for the other components and wiring needed, and come up with this. Dimensions are 235 x 175mm (240 x 180 when sides are on). It is important to have the batteries fairly symmetrical in the case as each one weighs a reasonable amount.

This is going to be really cramped in there by the time the project is finished. 29mm high is only just enough to clear the C cell's height. I need two buttons under the joystick mount and six buttons on the right, plus two shoulder buttons and and two on/off switches.



This will be tight! In comparison, the Nintendo 64 Advance is 270 x 185mm and didn't have C cell batteries in it, and was much thicker than this too. Some of the items moved a little before I took the pic, you can see from the pencil outline the size. All components are going to be very close together.

This will be quite a challenge.

My contact in Australia has posted his GP2x for me; once it arrives I can hack it apart; in the meantime I can crack on with the rest of the project, I know where everything will go, and the GP2x mobo will reside on top of the PSone mobo.

[Triton]

your 2700mah aas must suck cause back when i was using it a lot i was getting 2-3 hours on average from a somewhat worn out pair of 2200s, not running constantly overclocked or emulators much tho

[bacteria]

I have tried various quality ones in the GP2x, Anesman, Duracel, Uniross, Sony, Fujicell. Sometimes you get maybe a couple of hours, sometimes maybe half an hour, sometimes it doesn't boot before trying a new set. Unfortunately, it is the same scenario with my Kodak digital camera with its AA's.

It is quite annoying after all, playing a game for a short time, not knowing how long the batteries will last for, and then they die quickly. It might be the batteries, the GP2x, the fact it is overclocked to about 260Mhz; whatever. For some reason my MKII GP2x seems hungrier than my old MKI did (it fried, after a bad mod, I stupidly didn't turn the system off when soldering and a wire got lose and shorted the tiny capacitors!).

Without the LCD screen on the GP2x and running 6 C cells, it will be interesting to see how it fares!