Archive for category Homeware

This popular alternative, the MintyBoost kit is a simple "Plug-And-Play" solution for those who'd prefer not to get too technical.

At some point in your life,  you’ve probably tried the well-known mint (or gum) called Altoids. Known for being “curiously strong” its not just the mints that you’re getting when you purchase. The box these mints come in is like no other and is the perfect size for all sorts of tech projects. Slightly smaller than a deck of cards, it makes a great casing to anything you might house in it. One of the more popular uses includes turning the box into a portable iPod USB charger, capable of recharging your iPod for many more hours. Cheap and effective, its a great way to keep charged up on the road, and NOT in the air. Now before I begin, I’ll like to also mention that this is NOT a how-to for making your own portable iPod USB charger… instead I will be briefly skimming the surface on how you can engineer a better solution for however you decide to make yours.

So what does it take to power a USB port? Well for one, you need 5 volts and a pretty clean amount of amps to keep the current flowing for more than a minute or two. So lets look for a battery solution… A nine volt battery is about the size of two AA’s, provides more than enough volts, but falls short when it comes to the mA (milliamps), efficiency, and internal resistance it can provide. Using a 7805 (which refers to a very common linear 5V regulator) you can bring the 9v from the battery down to 5v and hold it steady for quite some time. Right here you have a very simple circuit that will work, but the efficiency of the battery would no doubt be under 60%, wasting just a little less than half of the battery.

Next up: those AA’s we were talking about. Cheap and effective, AA’s are always an ideal choice when it comes to quick power. So lets show some numbers real fast to show why AA’s are clearly more effective than a 9v battery:

Nine-Volt Battery: 9v x 500mAh = 4.5Wh
2 AA Batteries: 2 x 1.5v (each) x 3000mAh = 9Wh

For the same space, and probably an even cheaper price, AA’s provide just about twice as much power. So now that we know that AA’s are going to be our ideal choice for a battery, lets begin on solving the problems at hand. First off, it takes 5v (as we discussed earlier) to power a USB, so how are we going to do that with only 2 AA’s?  Well we need to make whats called a Boost Converter. Now I’m not going to walk you through how there made and why they work, but I will give you a small insight into whats needed to create this stepup converter that pushes 3v to 5v. Well your going to need a chip (also known as a DIP) to start out with. Now for size constraints, you probably want a 8-DIP chip. Running down the list of restrictions, your are going to want one with an internal MOSFET switch (so you don’t have to physically add one in), one that has a high frequency (so that the inductor we need later will be able to be small), and you also need to be able to supply around 100mA at 5v, and you need the chip to still run on about 2v or less. Using Digikey or Mouser, find the one you like the best…

Stick around for Part II in this mini-series on turning your old Altoids mint tin into a portable source of power for your iPod!