Filtered means that it is good for sensitive IC's as it will provide the most accurate selected voltage possible. This is accomplished by using filter/bypass/decoupling capacitors on the power rails to reduce noise. This power supply can source power from a range of power supplies within 7-14 volts @ 500ma. The lm317 can sink more than 500ma of current but at the sacrifice of having to use a lower voltage, this is because the LM317 has a max rating of 3watts total. Sinking 1.5 watts of power uses a fair size heat sink so if you want to have more power running though it you may want to move to a larger Voltage regulator.
This power supply is not suited (or needed) to power standard MCU's like the arduino uno or mega. It works great with a few tweaks to power a stand alone or breadboarded ATMEGA328 though, because the power is filtered and you have a nice easy way to adapt it to the same sources the standard arduino's use. Just beware that the ATMEGA328 is capable of drawing up to 560ma with just it's digital pins and this will stress the heck out of the power supply.
Step 1: Parts
For those of you who want to build it yourself AND save yourself a few bucks then that's what you'll learn to do. Lets start with the parts list:
1x protoboard - doesn't really matter what size as long as you can make it fit. 2"x2" should be fine but the heat-sink will likely hang off the edge unless you're creative
1x LM317 (type-t) Variable voltage regulator
1x heat-sink capable of dissipating up to 3 watts.**
1x 1N4001 1A Diode
2x 3.5mm pitch 2-pin screw terminals*
2x Break Away Headers* - (Right Angle or Straight depending on your design)
1x 100uF electrolytic radial capacitor
1x 10uF electrolytic radial capacitor
1x 0.10uF ceramic disc capacitor
2x 330ohm 1/4W 5% Carbon Film Resistors (standard resistors)
1x 1k ohm adjustable Potentiometer/Trimmer.
1x LED 5mm (your choice of color [may need to adjust resistor value])
Some wire - 22 gauge.
note - you'll also want to have some thermal compound handy for the heat-sink.
*The headers and screw terminals are how I decided to attach my power source. My supply is set up to accept power from either the screw terminals (from a 9v battery lead) or directly from a 7.4v 1600mah battery pack. These can be adapted however you want and I would suggest adding a 2.0mm DC Power Male PC Mount (2-pin) if you want it to work with a 9-12v wall transformer. That way it has a nice clean interface and you cant mess up the polarity.
** The heat-sink is important and there are several different ways to go about using it. The heat-sink is for the LM317 voltage regulator, it needs to be sinked for our purposes and while a 1.5 watt heat-sink is what i'm using and does a fine job for what i use it for, if your dropping a lot of power and using a lot of current you'll want to consider using a larger one. Just remember that this specific voltage regulator only supports up to 3Watts total even WITH the heat-sink.
It seems like a lot, but the total cost for just about everything here is less than $5 when ordered online. You can still get most of the parts from local hobby shops (or radio shack) for less than $10 and i'm sure if you've been working with electronics for a bit now you'll have most of these parts on hand anyways.
Step 2: Schematic
Step 3: Protoboarding
I'm sure some of you are wondering by now how you can measure what the output voltage is while setting the potentiometer. I simply use a multimeter and touch the top of the screw terminals. This can be a pain sometimes but you can get a small voltmeter for <$10. and if you don't already have one, you need one. As mentioned previously, if you're not interested in trimming values or using a multimeter to check the voltage frequently, you can simply use a switch and several calculated resistors rather than a potentiometer to give you exact values.
It's also important for me to note that if you hook up two power sources at once, something is going to cook (probably a couple things). One thing I would add to this design would be a power source selector. That way if you have a need to plug in both a wall jack AND a battery (or some other auxiliary source) you would know for sure that there is no way to accidentally melt your new fancy power supply.
Take some time to review the photos included. I tried to get good angles on everything so that if you're trying to follow it you should be able too. Also don't hesitate to ask if you need clarification on something, or if you see a correction that needs to be made.
Step 4: Next steps and modifications
The other thing you may have seen are the much smaller versions of this power supply here (once again usually with at least one of the above mentioned alterations). The key to making those is getting the PCB designed and printed out. For the fun of it, I made a fairly simple single sided PCB that should do the trick just fine. I used express PCB and the print cost for 10 of these boards is roughly $90 through the express pcb supplier. Printing your own is also fairly easy and there are plenty of other instructables that will help you with that if you're interested.
Step 5: Help!
Also don't hesitate to ask if you have any questions.