Here is a cheap and easy 3.3v converter!

vskid · Post by **vskid** » Fri Jun 15, 2007 9:42 am

Felino wrote:Firstly, you can not, i repeat can NOT use AA batteries, they will NOT supply the current to wither devices, and charging 7 AA's is not fun. Use a 7.2 volt pack like everyone else. The reason yur batts are getting hot is you are drawing WAY to much current from them, and are damaging them..

He said that he is just using the AAs for testing and that he'll get sub-C's for the completed project. With the 2 sets of 6 AAs in parallel, I see no problem in using them, they're fine for testing.

bacteria wrote:Reason for 7 batteries - if you recharge 6 batteries, they hold about 8.45v. As you say, leave them for a short while (day or two) they reduce to about 1.25v or thereabouts. This reduces them from about 8.45v to 7.5-7.7v. This is fine, but means they don't last for long before there isn't enough voltage to power the PSone screen (tried this); in contrast, freshly charged batteries give their maximum playtime.

My logic is this (please comment): if you intend to play your games system immediately after the batteries recharge, you are fine with 6 batteries. If you are happy to use batteries charged a day or two before (no issue if you have many of these things anyway), then you would be better using 7 batteries (giving about 8.8v instead of about 7.5v). Best to use a multimeter first to find a set of 7 batteries which give under 9v to protect the PSone screen. 7 batteries would not only give maximum playtime, but, in theory, give 1/7th more playtime too - if you get for example 1.75hours on freshly charged AA's, the extra battery (7th) might raise this to about 2 hours, ie extra 15 mins playtime (is this right or am I talking waffle)?

Your logic is good, adding the 7th battery even increases the total watt-hours of the battery pack. The problem I see is that you could draw too much power from your batteries if you don't have some sort of protection circuit or a battery meter so you know when you're abuot to start causing damage and can stop playing. You would still get more play time even with the protection (higher volts, less amps drawn, same watts), but I don't know if chargers would like charging 7 cells, or you could hate pulling them all out and charging them separately in 4 cell chargers.

bacteria · Post by **bacteria** » Fri Jun 15, 2007 10:12 am

vskid - thanks for the supportive comments.

Do you have a more information about the protections circuits and what they do, and the circumstances you use them? If the total volts of 7 cells are under 9v, would that be ok?

My battery charger doesn't cut-out and can also charge 9v batteries (2 of them), so I put in two sets of 6 batteries into the recharger (12 cells) and left them for a couple of days, they seemed to charge ok and didn't even get warm. I need to further test this, but it would mean they could potentially be permanently installed in a system and charged together. (any reason not to do this??)

vskid · Post by **vskid** » Fri Jun 15, 2007 10:32 am

bacteria wrote:Do you have a more information about the protections circuits and what they do, and the circumstances you use them? If the total volts of 7 cells are under 9v, would that be ok?

I think that 1v per cell is the point of no return for NiMH cells, if it gets that low, its dead forever. So the problem with 7 cells is that the N64 and screen die when the voltage gets to about 7.2v, which is very close to the 1v per cell death point. So having the portable turn off at 7.5v or a power indicator that shows dead at a similar voltage would keep the cells at a safer voltage. I'm not sure about 1v being the death point, I couldn't find anything about it in the few minutes I searched, but thats the number that keeps popping into my head.
I think timmeh might know more about whats safe and a way to protect the cells.

bacteria · Post by **bacteria** » Fri Jun 15, 2007 3:32 pm

vskid - ok right, I wasn't aware of this - thanks. Ok, that means 6 cells only. Appreciate you letting me know.

I managed, successfully, to recharge 12 AA batteries at the same time in my (normally 4 at a time charger) - 2 x 6 batteries in their holders, connected to the two 9v recharger connectors. The charger doesn't cut-out - left them for nearly 2 days, seem to have recharged all 12 fine. Interesting...

Felino says you can run the whole thing off one 7.2v battery ("like everyone else") - however I looked at the majority of comments on the N64 forums (took hours!); found the following - quoted figures from various members:

a) 12v only needs 9.6v, which can run from 8 AA's (max 10) it says.
b) 3.3v line could run via 3 x AA's, although it might fry your mobo if you are unlucky; some 3.3v lines are ok at 3v and up to 5v, but no guarantees

Given this, I don't see how a 7.2v battery is adequate as Felino states - you need 9.6v for the 12v line and (and as you say) the PSone screen dies at 7.2v (mine dies at 7.4v). How therefore can a 7.2v battery work?

Unless I am missing something, it appears that you either:
a) have a single battery pack rated between 9.6v and 12v, use this for the 12v line, a regulator for between 7.5v and 8.5v for the PSone, and a regulator for the 3.3v line, or
b) as I listed above - one pack of batteries around 8.5v for the PSone and a second pack around 10v-12v for the 12v line, fan, and a 3.3v regulator for the 3.3v line (or as some people have done, with a resistor).

vskid · Post by **vskid** » Fri Jun 15, 2007 3:48 pm

The 12v line on the N64 can go down to 7.2v. A regulator to get 3.3v from the 7.2v would be best, then the whole thing would die as one.

Felino · Post by **Felino** » Fri Jun 15, 2007 10:07 pm

Is your screen LED modded, thats probably why it dies at such a high voltage. Regardless, all your system will run off 7.2 volts, for my portable latter in the year, I have tested this, and it is fine.

-Fel

P.S. I didn't mean to sound as rude as i did before.

Neildo_64 · Post by **Neildo_64** » Tue Jun 19, 2007 3:57 pm

Sorry, no help here. Just showing that an N64 and screen will run on AAs. I was running my N64 and screen from 8 AA 2500maH cells along with a TI dc-dc converter and a tiny fan.

I can't remember how long they lasted. I'm thinking these only lasted somewhere around an hour before the screen went off.

timmeh87 · Post by **timmeh87** » Tue Jun 19, 2007 4:57 pm

the dc-dc converter reduces the current draw by like 40%. if you had a linear reg in there you'd be less likely to get that to work. just sayin.

oh and regarding the deadness of ni-mh cells: 1v/cell is definitely dead, but it wont completely destroy your batteries or anything. I've brought some down to like 0.8v before. It wears them out a lot faster but they are pretty friendly about being abused.

also about custom protection circuits: use a comparator and a mosfet. One day ill write up my flashlight project and you will see what I mean... one day....

bacteria · Post by **bacteria** » Wed Jun 20, 2007 2:39 am

Neildo_64 - Interesting. Thought that 8 batteries would blow the PSone screen as exceeds 9v. ? . I will be using a bigger fan as small fans are a bit noisy - one I will use is about the same size as the N64 cartridge, so can sit on the rear of the case under the re-positioned cartridge.

I am awaiting (still) my N64 screwdriver to come in the post so I can take the casing off the N64 and start the project. I have a stack of powerful AA batteries anyway, so once I get my system working (even for a short time) fully, I will probably get 6 x C cells - seen them on the net at about 5000mAh NiMH, to drive everything (if not, sub-C). Using AA's at the early stage is fine for two reasons - 1) proves everything works fine (before spending on better batteries - especially if I end up giving up on the project in the meantime if I keep frying boards!), and 2) works on more stress (eg faster drain, and a test of the performance of the 3.3v line in these conditions - if everything ok in this condition, will be better in more stable, higher capacity conditions, logically).

In regards to this car adapter - I will connect directly to the two pins on the step-down regulator, and test the system (with AA's, reasons above) and see how it performs. If the N64 works fine until the batteries die, I know I am ok with it; if the N64 is unhappy and is unstable with the 3.3v line with the adapter, I will look have to try the t1 board or similar. I need to satisfy my curiousity at this stage however - I like to experiment

One question - heatsinks - I note the system in the pic has none and is running ok - I figured if I use my nice big fan over the N64 board (with airflow of course) I should be ok without using heatsinks, and will keep things cool (and flatter) - am I right?? My case will be wood this time, for a smooth finish and strength, using thin MDF and a 1mm thick smooth wood top layer for finishing - figured this would be sensible, given the heat the N64 generates.

Felino · Post by **Felino** » Wed Jun 20, 2007 6:45 am

USe heatsinks man, even if they are small, otherwise there is nothing for the fan to blow away...

bacteria · Post by **bacteria** » Wed Jun 20, 2007 9:08 am

Ok!

timmeh87 · Post by **timmeh87** » Wed Jun 20, 2007 11:56 am

I agree, heatsinks are definitely a good idea. the main processor/ram get really, really hot without them. you can get some pretty aweome "spiky" aluminum ones that sit really low. plus you can always mod them to fit around things.

Neildo_64 · Post by **Neildo_64** » Thu Jun 21, 2007 1:54 pm

bacteria - About the 8 AA cells, I should actually have a 7808 in there, but its not hooked up in that picture. This was after the batteries were a little drained(~8V on multimeter). The screen does go crazy without the 7808 and fully charged batteries.

As far as my fan, it is almost silent. I have 2-3 more fans that size if somebody wants one and can't find one. The one in the pic I bought at radioshack, the others I found.

USE HEATSINKS - the surface area of the ICs aren't enough to spread the heat well enough to blow it out with a fan. The heatsink takes the heat from whatever it's attached to and becuase of all the fins, the surface area to blow heat from is greatly increased. Even if the heatsinks are 1/4" thick, they still add a LOT of surface area. Quick version - Heatsinks are a good thing to have.

bacteria · Post by **bacteria** » Thu Jun 21, 2007 4:59 pm

A few comments and updates:

1) Take point made about heatsinks - however, as the N64 uses a flat piece of aluminium over the 3 processors as its heat dispersal, how about I hack this to a better size and drill holes in the piece so there is plenty of airflow from the fan; the heat goes to the aluminium piece (as now), the fan cools it down...?

2) Neildo_64 - how big and how thick is your fan? I could be interested in two of your fans (how much?), mine is virtually silent but it is a bit thick for my linking.

3) I had an AA battery go down to 0.38v for some reason, recharged it, back to 1.39v again (just thought I would mention this).

4) Tried the car adaptor today (I just got the special screwdriver). Used a pack of 8 batteries (AA); only got 2.8v out of it, so this confirms it, there isn't enough out of it to be useful via batteries, and the power to the other line dropped too (ie N64 mobo didn't work); also it seemed to use a lot of power too. Oh well, tried it.

5) Realised why the PSone screen dies under 7.5v - logical really -the PSone power supply is 7.5v not 7.2v, so it expects 7.5v!

6) My N64 mobo fried, I was messing about with the 3.3v line and I got some smoke - mobo dead now.

I have 2 more N64's - all of these are serial numbers starting with "13" so should be able to be made RGB.

I made a decision: I only play games at home or work, there are a lot of hassles with battery portables and especially the N64. I think what I will do is 2 versions of a N64 project - project 1 to make an N64 portable as small as I can, running off one wall socket; and version 2 (later, when I have experience making version 1) with a fully portable battery one. I can't afford to keep frying boards!

I figured I would use the power adapter from the PSone screen (came with the unit - (7.5v DV output, 3amp), to power the N64 and PSone screen, and see if the car adapter I have works properly with mains power (7.5v in) - if not, I will have to get the TI board (problem is I am in the UK and they don't seem to want to ship to the UK).

Comments??

bacteria · Post by **bacteria** » Fri Jun 22, 2007 4:16 am

MAJOR UPDATE:

Wow! I was wrong - the car adaptor works great!!!

Hooked up my PSone power supply (came with the screen - mains power > 7.5v 3amp), to the PSone screen, the car adapter, fan (0.08amp) and the N64. Rather than soldering to the N64 input pins directly, I soldered the wires to the connector I took from the official N64 power supply end (just a choice, I can solder directly to the N64 mobo at a later stage if I need to).

As you can see from the pic below, everything works. The reason it had a problem with the batteries was its draw - no issue with mains power.

I figured:

The PSone screen (unmodified) I believe has a draw of about 0.8amp, the fan 0.08amp, the N64: 3v line up to 1.3amp the 12v line up to 0.8amp. This totals 2.98amps at full load - fine!! Sure enough, it works! Tested it for a couple of minutes only (no heatsinks yet - although will try hacking part of the N64 metal sink.

As I said earlier in my posts, new people to the scene can make new discoveries!!

At a later date I will make one with batteries only, however, this allows me to make a small N64p, plug it into one mains adapter and run everything - saves a lot of faffing about with batteries which only last a few hours then drain; have issues with things going "wobbly" etc - I only play games at home or work, so there is always a power supply about, so not a problem.

Anyway, I have proven this car adapter works. I also have a fried N64 mobo from my last attempt, so I can practice taking off components (the video out, cartridge expansion slot, etc).

Yes, I know the fan is big - I need to find a slimmer one which is dead quiet (before anyone comments on this!). Ignore the rest of the stuff in the pic - you can see what is relevant!

I have decided to do what others have done, and start a new topic on this project for people to view - might help someone.