Help with powering LEDs

[VsUK]

I am attempting to put in a back light for my sons Gameboy Advanced. I know what i need to do to put it in, however I'm a little lost on how to power the LEDs or which LED would shine the brightest with the lowest power requirements.

The mod job would be using the console's own 2x 1.2v 1600Mah rechargeable batteries. However I'm confused on how to calculate what power requirements needed for LEDs to power up & what Resistor type i need.

I went to this site **broken link removed** which calculate's things for you, but every time i put 2.4 for the vaultage & put in the LEDs info I've seen on ebay before i purchase i always get that I'm not providing enough vaultage to power the LEDs.

Not done anything like this with LEDs since the mid 90s in my school days lol so any help would be grateful.

Thanks

 

[Rusttree]

You probably won't be able to power the LEDs directly from the two 1.2V batteries in the Gameboy. There are two main reasons for this:

1. The battery voltage may not be high enough for the forward voltage of the LEDs you choose (this is mostly likely true if you're looking at white LEDs).

2. With any battery powered device, the battery voltage drops as the batteries drain. A constantly changing voltage source can be problematic for any circuit.

In fact, the Gameboy itself almost certainly does not run directly from the batteries for both these reasons. A common solution (and probably what the Gameboy uses on its circuit board) is a boost switching regulator. This type of voltage regulator exploits the properties of an inductor to create a higher output voltage than input voltage with a very high conversion efficiency (usually >80%). So, for example, you can design your circuit to output 5V, regardless of the state of charge of the batteries. That should give you enough voltage to run any LED you choose.

 

[VsUK]

Hi, yeah i know i cant run directly from 2 1.2v batteries & know i need resistors & i did come across the DC to DC Converters but the only ones i was able to find was 3cm x 1.5cm in size, far to big to fit inside the gameboy advanced case. I noticed some 4 pin DC to DC 12v to 12V but i can't find anything from a starting 2.4v. Do you or anyone have any suggestions on where to look for them. I'm from the United Kingdom so please bare that in mind.

Thanks for the quick reply btw

 

[Rusttree]

You can go way smaller, but you'd have to put the circuit together yourself using surface mount parts on a PCB. Is that a route you're willing to consider? If so, we'll be glad to step you through it.

Alternatively, you could try to reverse engineer the Gameboy circuit board and see if there's a regulated voltage you can tap into. That's risky, though, because any power line you find may or may not be able to handle the additional milliamps from a couple LEDs.

I've never owned a Gameboy, but I feel like I've seen backlight accessories that you can buy. Where do those plug in? Can you tap into the same power source?

 

[VsUK]

Hi, i have attached an image for you to see exactly what i plan to do. If making my own DC to DC converter would be easier then i would love to give it as go if your willing to help. I just need to find the components first which is usually the hard part

I do have a backlight accessory as you said are about & that has its own 2x AAA battery slots. If i need to i can use that as it fits over the screen with its screen magnifier which i can use for the power source, however if possible i would like to tap into the console's own power source so there's nothing the kids can pull off & destroy as it will be all inclosed into the solid case for the console.
View attachment 64261

 

[MrAl]

Hi,

There are a ton of chips that take a small battery voltage as low as 1.2 volts and convert it into a 3.5v or even higher output for driving one or more LEDs. These are basically the simplest solutions out there and are super small in size because they are surface mount parts. One manufacturer for example is Zetex,which make a bunch of ic's just for LED driving, but there are others too like Maxim. You'll find something on their sites im sure. They usually have complete application notes to go with their products too which leaves little guesswork.

 

[VsUK]

I found the site Maxim already, but it didn't look like a place where you can purchase small quantities of parts. I'm a novice when it come's to things like this as it was not something that interested me until recently. I am from the United Kingdom so ordering would need to be cost effective, as i have seen some diode's costing 1/5th the cost of delivery. So if anyone could point out some products, like on ebay.co.uk or other place's that i can look up that would be great. I'm an easy learner, just don't know what does what atm

 

[MrAl]

Hi,

Well actually you go to those sites to look for the products, then you go to another site like Digikey to buy them in single quantities. I recommend getting at least two in case one blows out because these blow out when they are not used right the first time.

 

[Rusttree]

There's actually a sticky thread in the General Electronics Chat forum here. It's called "Where To Buy Electronic Components And Parts!" and looks like there are a couple of links for UK-based distributors. Take a look there.

What you're looking for is a switching regulator chip. Without getting into the theory here, they're DC-to-DC converters that exploit the properties of an inductor to generate a higher or lower voltage than the input. They're very high efficiency and can handle large currents. Some are made specifically to drive LEDs while others are for generic use. As long as the input voltage, output voltage, and current rating matches your needs, it doesn't matter too much which one you get.

To pick one out, you can go directly to a manufacturer's website (like MrAl recommended), find a part that fits your needs, then go to a distributor's website and see if they have that part. Alternatively, you can just go to the distributor's website and use their search engine and filter down to what you're looking for. All of the links in that sticky thread are distributors. When you search for switching regulators, they'll probably be categorized under "DC - DC converters" or "Power Management ICs" or something similar.

 

[VsUK]

Right i see, yeah i get it now Now all i need to know is what parts i need for the surface mounted on my own PCB board. I presume it cant be just the dc to dc step up module & then the connections +/- in & the + out right?

Edit

Thanks Rusttree for the info, u posted just before i did