So I was busy homebrewing on my NDS, even bought myself a DSerial board to use it as an ultraportable serial/debug console. I had a few ideas for the much faster, native parallel interface too, so when we were sending out boards at work, I threw my own “DParallel” onto the layout. The boards came back, and we had to cut them apart…note to self: DO NOT let your machinist saw apart your boards on a huge gritty band saw. As is semi-common practice (and just like on the DSerial) I laid out a big VDD (main system power) plane on the bottom of the board and a big GND plane on top. Before inserting the board, I peered down the sides of the card slot to be sure they weren’t metal that would short against the sides of the board, and even performed some quick “due diligence” checks with an ohmmeter to be sure I didn’t do anything stupid (such as somehow shorting VDD and GND together) that would result in frying my DS.
Satisfied that all was well, I popped the board in, hit the power switch…and proceeded to fry my DS :-(
Turns out that the top and sides of the card slot are plastic, but the back surface (hard to see in an all-black DS) is METAL, and it’s connected directly to ground. Combine this with a big VDD plane in direct contact with it, and some rough board-sawing leaving some exposed copper on said plane, and a heap o’ trouble ensues.
Anyway, due to some smart engineering by the big N, I am spared from my own stupidity (it just blew an internal fuse). Googling for Nintendo DS power consumption specs to figure out what replacement fuse I needed, I saw just forum posts with educated guesses ranging from ~ 300mA to upwards of 1.5A. So while I had it under the knife, I decided I’d settle the question once and for all.
Current Consumption Numbers:
All measurements taken on a DS Lite “revision as of Jan. 07″ at 3.70VDC, the nominal voltage of the battery pack.
Quiescent (power OFF, just running the realtime clock)…1.3uA! (This is Sweet F-All.)
NDS Boot screen, no cartridges installed…
Screen brightness 1 (lowest) : 54mA
Screen brightness 2 : 81mA
Screen brightness 3 (default) : 128mA
Screen brightness 4 (brighest) : 180mA
All the following measurements taken at Brightness level 3 (default) unless otherwise noted.
DS Download Play (Wi-Fi module active/scanning) : 177mA
Pictochat (Wi-Fi active) : 140-184mA
With Supercard SD installed….
NDS Boot screen (Pictochat / Download Play selection screen) : 159mA
GBA mode (bottom screen off, probably ARM9, 3D engine and a couple other things powered down too) : 98mA
SuperCard home screen: 165mA
Playing a movie using Moonshell (bottom screen off, 2D) : 118mA
Moonshell ‘idle’ (both screens off) : 67mA
Metroid Prime Hunters (both screens active, 3D, heavy Flash seeking) : up to 190mA
Running “WiFi_Example1″ (both screens and WiFi active) : 228mA
WFC “Search for access points” : 228mA
“Almost Worst Case”: Running Wifi_Example1 at full brightness: 278mA
Worst case seen: ~ 290mA
1st brightness level: add 18mA to base
2nd brightness level: add 24mA to 1st brightness
3rd brightness level: add another 47mA…
4th brightness level: add another 52mA to all of the above
(Total power savings by keeping lowest brightness: 126mA)
SuperCard SD: add 31-37mA while idle…a bit more while reading/writing the SD.
Bottom screen @ default brightness: save 47mA by turning it off
WiFi enabled (“new” 1/2007 DS Lite wifi chipset) : add 49 ~ 63mA, varies based on what it’s doing.
Around the tail end of 2006, Nintendo switched to a different WiFi chipset (sorry, can’t find any more info online from DS forums, etc…only the code changes in libdswifi CVS to accommodate it). This is the one I have. Power draw results for the previous chipset could vary from this.
Fictional (best case) playing times:
Numbers obtained by dividing battery capacity (1000 mAh) by actual current consumption. The “mAh” (milliamp-hour) rating means the battery can in theory supply 1,000mA for 1 hour (or 100mA for 10 hours, etc.).
These are rough ballparks that assume 100% conversion efficiency, extracting 100% of the power out of the battery, and all kinds of other things which do not reflect reality. Your real numbers will be lower.
Brightness 1 (min), no cartridge: 18.5 hrs
Brightness 2, no cartridge: 12.3 hrs
Brightness 3 (default), no cartridge: 7.8 hrs
Brightness 4 (max), no cartridge: 5.5 hrs
As you can see, backlight setting has a large impact on total run time!
Let’s assume default brightness for now…
Pictochat / Wifi download play: 5.6 hrs
Running SuperCard SD: 6.1 hrs
Running SuperCard SD with intensive game: 5.3 hrs
Running SuperCard SD in GBA mode: 10.2 hrs
Running Wifi app/game from Supercard SD: 4.4 hrs
“Low Battery” threshold: about 3.70V
Low battery automatic shutdown: about 3.44V
Startup current profile, no cartridges:
Initial phase: 20mA (screens off, power indicator dimmed)
Second phase: 85mA (screen backlights on, still initializing things)
Fully initialized: 128mA (default brightness)
Fuse sizing (for everyone else who did something dumb and blew F2): I had some 500mA 0603 surface mount fuses laying around (Rezu project represent!), so I used one of these. I think it’s a good number given the above. Worst-case power usage I could produce was just a hair under 300mA, but some other DS slot 1/2 cards (games, flashcarts, rumble paks, specialty cards like the Opera Browser cart with onboard RAM) may draw more juice (still, I doubt it would bring the total over 500mA). Even if you’re sticking your own Pentium 4 accelerator card in there, I wouldn’t advise sizing the fuse above about 750mA, absolute max. It’s there in part to keep the Li-Ion battery pack from going all Sony Vaio on you and melting your pocket into hot slag if something in the DS shorts.
Text on the new Mitsumi wifi module:
FCC ID: EW4DWMW006
(“R” symbol) 007NTCUL0121
Made In Philippines
Mitsumi’s web site provides no evidence that this module actually exists, of course.