Alley Beach
Offline
clovis CA

based on what nitro said on his blog, i took it upon myself to try and figure out how to do this.
first, i googled some stuff. i guess using a 7805 (5v regulator) would be the most inefficient way to drop down voltage. somewhere i read that a 9v battery would be drained 45% faster with a 7805 than regular use. so thats out of the question.
so i thought about a voltage divider, though this sounded like a good idea in theory, it wouldn't be suffice under load. i tried it anyways. didnt work...
after that i was testing to see if a 9v battery with a resistor on it would work. so i put a 100ohm resistor in series. didn't work and got super hot. this is because of the current. i added a second 100ohm resistor in parallel with the first. didnt work. but this time the back light would flash for a brief moment. i added a third 100ohm resistor in parallel, and it turned on smile
sweet.jpeg
ok, so i tested the voltage. the 9v battery was actually running at like 8.4 volts... oops. but anyways
the dmg was getting +-6V!!!! (i went straight to the battery contacts, cause 4 AA batteries is about 6v wink )
so, if you want to do the math you can do the whole

            1
______________
1         1            1
-     +    -      +     -
R1       R2         R3

or you can cheat with a multimeter wink i did both, and i should've had 33.3- ohms if i did the math right, but i had a little over 32ohms
anyways, if someone can check to make sure this is ok to do with the method i've chosen, id appriciate it. its 1 in the morning and i had nothing better to do. hope this helped smile

edit: forgot to put addition in the formula tongue

Last edited by Alley Beach (Feb 16, 2013 9:25 am)

Teh D3th St4r
Offline
Santa Cruz, California

OKAY! I tried it. It works. Left it on a timer, and I'll tell you how long the battery lasts tomorrow.

Alley Beach
Offline
clovis CA

did you set it on a timer at solid 9v? in nitros blog it said itll destroy the lcd :L

Teh D3th St4r
Offline
Santa Cruz, California

I have it dialed down to 5.8v running it through some resistors and a converter on a breadboard right now.
Gonna see how everything goes, then I'm gonna experiment with a LTC3789 buck boost converter. That should be significantly more efficient, and have comparable battery life to the 4 AA's.

ashimoke
Offline
Czech republic
Vex wrote:

Id also be happy with finding a confirmed recharble battery set that you could perma install and instal a port it could charge from..maybe even the port already in the dmg.

Not exactly the same, but:

Gameboy pocket with mini usb (for charging only). It has a li-po battery similar to this one (600mAh) and this lipo charger (cut down in half). You can also get the charger at sparkfun.
I have yet to put the battery life in a serious test but it seem really good (at least compared to the crappy AAAs I've been using before). I can also use my USB EMS with no problems.

Teh D3th St4r
Offline
Santa Cruz, California

SICK! This (at 6v) is what I need for my keyboard!

ashimoke
Offline
Czech republic

also: this is the smallest buck converter I found on ebay (20 x 20 x 5mm)

nitro2k01
Offline
Sweeeeeeden

A voltage regulator is just a self-adjusting "resistor" (also known as a transistor, you might have heard of those) that does the same thing as described in the calculation, but over a big voltage range. From about the output + 1 V up to when the regulator circuitry breaks down. The downside of either the resistor method or the regulator method is that energy will be wasted as heat to warm up that component. The downside of sing the resistor method in particular is that the voltage seen by the Gameboy will go down as the battery's voltage goes down, which makes  the Gameboy use more current to maintain the same power. You might also get a change in LCD contrast when LSDj plays versus when it doesn't, as it enters a power save mode when it's not currently playing.

Thing is, the Gameboy has a so called switching voltage regulator which can handle a wide voltage range, from at least 4 V up to maybe 9 V or more. The voltage regulator is of the switching variety, which means it regulates the voltage level by turning the input voltage on and off at a high frequency. The DMG regulator also has a transformer which allows it to both boost and "buck" (lower) the voltage.

The potential problem, apart from going outside the range that the components in the regulator can handle, is that the LCD supply voltage will vary with the battery voltage. The increased voltage with increase LCD voltage could (Not will. Read exactly what I said.) destroy the LCD on the extreme contrast setting. This remains to be seen, however and it should always be safe for the LCD as long as the dial is set to a normal, legible setting.

Teh D3th St4r
Offline
Santa Cruz, California
ashimoke wrote:

I can build a smaller one.

nitro2k01 wrote:

That's what the buck boost converter would be for. No matter what the battery voltage, the output will always be 6v. Battery down to 2.3v? Output will stil be 6v. So you'll have power right up until you don't...

Last edited by Teh D3th St4r (Feb 16, 2013 11:27 am)

nitro2k01
Offline
Sweeeeeeden
Teh D3th St4r wrote:

That's what the buck boost converter would be for. No matter what the battery voltage, the output will always be 6v. Battery down to 2.3v? Output will stil be 6v. So you'll have power right up until you don't...

That's what I'm saying, though. The DMG already has such a converter (even if I called it regulator). When the voltage of four AA batteries, or one 9 V battery is 2.3 V, no boost converter in the world will save you, because the battery's internal resistance will stop you from getting enough current to power the Gameboy. In my test, the Gameboy used 120 mA at 2 V. Trying to do that with almost fully decharged batteries would probably be impossible.

Teh D3th St4r
Offline
Santa Cruz, California

2.3v was just an example, and I haven't tested it. It was simple nonsense, and your semantics aren't necessary.

ashimoke
Offline
Czech republic

Yeah right, I think nitro should just shut up. You can build it smaller anyway.

nitro2k01
Offline
Sweeeeeeden

Well, from your reply I wasn't sure if you understood my post, so that's why I pointed out the regulator/converter thing. Since you mentioned 2.3 V, even if a made up number, I assumed that what you were addressing was the problem of the voltage being too low when the batteries are about to run out.
With regard to the LCD, the first thing to do is to establish whether the LCD is at risk at all. If not, you can just use a 9 V battery and be done with it.

dsv101
Offline
Medina, Ohio

Just letting you know, you should know that yes a dmg will run from a 9v battery, it is the battery life that should be your concern.

Talking alkeline batteries, here is the comparison of mili-Amp hours (mAh):

AA: 1800-2600 mAh
9v: 565 mAh

As you can see the juice in a standard alkeline AA is 3.18-4.6 times more.

Talking lithium batteries:

AA: 2700-3400 mAh
9v: 1200 mAh

As you can see the juice in a standard lithium AA is 2.25-2.83 times more.

You can read up about them here:

http://en.wikipedia.org/wiki/AA_battery
http://en.wikipedia.org/wiki/Nine-volt_battery

I would also recommend looking here:

http://en.wikipedia.org/wiki/Linear_regulator

However,

nitro2k01 wrote:

With regard to the LCD, the first thing to do is to establish whether the LCD is at risk at all. If not, you can just use a 9 V battery and be done with it.

Teh D3th St4r
Offline
Santa Cruz, California
ashimoke wrote:

Yeah right, I think nitro should just shut up. You can build it smaller anyway.

Dude, Nitro is hella cool. Visit his website... you'll learn things.

nitro2k01 wrote:

Well, from your reply I wasn't sure if you understood my post, so that's why I pointed out the regulator/converter thing. Since you mentioned 2.3 V, even if a made up number, I assumed that what you were addressing was the problem of the voltage being too low when the batteries are about to run out.
With regard to the LCD, the first thing to do is to establish whether the LCD is at risk at all. If not, you can just use a 9 V battery and be done with it.

It was intended to be a wild exaggeration (I know you can't boost voltage x2) and I think 3.4-5v is about as low as you can get...
Anyway, running 9v strait into the DMG is a colossal waste of power, as the regulator will just convert any extra power into heat, and I'm not sure the regulator in the gameboy can handle 9v for an extended period of time. My idea simply extends battery life and eliminates the risk of damaging your DMG.

Last edited by Teh D3th St4r (Feb 16, 2013 6:49 pm)

Alley Beach
Offline
clovis CA
Teh D3th St4r wrote:

It was intended to be a wild exaggeration (I know you can't boost voltage x2) and I think 3.4-5v is about as low as you can get...


Im almost positive the output of the DMG's power board is 5V (see that pun there wink ) so 5v is the highest smile

Last edited by Alley Beach (Feb 16, 2013 7:58 pm)