I lit up my kitchen counter top with modern LED lighting for just over $20.00. My exact cost was $20.62 ($7.63 + $12.99) because I had everything else laying around. You can do yours for less than $30.00 depending on what donor parts you already have laying around!
Here is what I used:
12 VDC 2 Amp Universal Power Supply - $7.63 from Amazon Prime. http://www.amazon.com/gp/product/B002FH54L6/ref=oh...
Super bright 5 meter (over 15 feet!) LED strip light - $12.99 from Amazon Prime. http://www.amazon.com/gp/product/B00JQV6NNC/ref=oh...
Donor power cord from a desk lamp I was not using
Rotary power switch from the same cord, relocated to close to the plug end. If your cord does not have a rotary power switch, they are $5.24 from Amazon Prime. http://www.amazon.com/Leviton-423-3-6A-125V-3A-125...
Fine gauge red and black wire - I used some 24 gauge wire I had laying around.
You will also need a soldering iron and some electronics solder, not plumbers solder. Plumbers solder and plumbers solder flux both contain acid that will eat through wires!
Step 1: Scrounge a Used Power Cord From a Desk Lamp
I scrounged a power cord and rotary power switch from a desk lamp I was never going to use again. Problem was, the switch was on the lamp end of the cord and I wanted it near the plug, so I cut the plug off short of the power switch and removed & relocated the switch.
Step 2: Prepare the Power Cord for the Rotary Switch
Power cords with 2 blade plugs on the end contain two wires. To install a rotary power switch you need to first remove a short section of one of the wires.
Start by cutting half way through the cord in two close places then cut out the piece between.
Next you need to separate the two wires a little. Don't remove any insulation.
Step 3: Assemble the Rotary Power Switch to the Power Cord
Remove the center screw and separate the two halves.
Lay the wires in the non-switch half. You can see from the second picture how the complete wire routes around & past the center screw while the wire with the section missing ends short of the screw.
Then assemble the two switch halves and assemble & tighten the center screw.
Step 4: Measure Your Power Cord Length
Measure from the outlet you will plug into to where the power supply will be mounted.
The cut off the excess power cord. If you aren't sure measure again before you cut.
Just remember, don't plug the power cord in yet!!!!
Step 5: Prepare the End of the Power Cord
Make sure the power plug is not plugged in first!!!
Before the end of the power cord can be attached to the power supply the end has to be split and stripped. The pictures show step by step.
Step 6: Wire AC Power to the Power Supply
The power supply I bought is not that large. It will likely fit in the palm of your hand.
Look at the end and you'll see a set of screws with the following labels.
L Incoming AC Power
N Incoming AC Power
V1- Minus 12 VDC out
V+ Plus 12 VDC out
Flip up the yellow safety cover and attached the prepared wire ends under the L and N screw terminals.
Make sure the wires are tight and there are no stray wires when you are done.
Step 7: Prepare the First Set of Red & Black 12 VDC Wires
Measure from where the power supply will be mounted to the end of the first LED string.
Cut the red & black wires to the correct length and strip the insulation off the ends of the wires.
Step 8: Attach the 12 VDC Wires to the Power Supply
Attach the black wire to the V- screw terminal and the red wire to the V+ screw terminal.
Then snap down the yellow safety cover.
Step 9: Prepare the Strip Lights
The roll of strip lights I bought comes with a 5.5mm X 2.1mm power socket already installed, but because I am wiring in a power supply that does not have a power plug I just cut off the end with the socket.
You'll notice that after every few LEDs there are a set of 4 closely grouped copper pads. The LED light strip is designed to be cut apart at any of these locations.
Once you cut the end with the power socket off you will need to tin, or add some solder, to the two pads.
Step 10: Attach the 12 VDC to the LED Light Strip
Strip the other end of the wires you attached to the V1 and V+ of the power supply, tin the wire ends then solder them to the end of the LED light strip you tinned earlier.
IMPORTANT!!! - Notice that there is a + and - marked on the light strip.
The 12 VDC + (red wire) will always connect to the + terminal.
The 12 VDC - (black wire) will always connect to the - terminal.
Wire them backwards and the lights will not come on!!!!
Step 11: Test Your Work
Now you can finally test your work!
Plug the power cord in. If the LEDs don't come on right away then turn on the rotary power switch.
If the lights don't come on then most likely you have the red and black wires swapped at the power supply or at the light strip.
After testing, unplug the power cord!
Step 12: Measure Your Individual Light Strips
Starting with the first cabinet, the one where the power supply will be mounted, measure each cabinet length.
Just like earlier when you cut off the plug end, cut the LED light strips into smaller pieces that will fit under your cabinets.
Just like earlier, make sure all of the cuts are between the 4 copper pads.
Step 13: Measure Your Jumper Wires
You will need to connect the individual LED light strips together with jumper wires.
Measure the lengths you need then cut.
I ended up with 2 sets, or 4 wires, 2 red and 2 black. The jumper wires were all the same length for my cabinets but they may not be for your cabinets.
Step 14: Tin Your Jumper Connections
Strip and tin both ends of your jumper wires.
Then tin the copper pad ends of all of your LED light strips except for the very last one.
Solder your jumper wires to the ends of your LED strips.
Just like before, make sure the black wires go to the pad marked - and the red wires go to the pads marked +.
Step 16: Time to Test Again
Now it's time to test again.
Plug your power plug back in and make sure all of the strips light up.
If some do and some don't the most likely cause is you soldered the wires to the wrong terminals!
Step 17: Mount the LED Light Strips
These light strips come with double sided tape already attached to the back side.
Starting with the furthest light strip, carefully peel back the double sided tape backing and press the strip to the underside of your cabinets.
Step 18: Mount the Power Supply
Using 3M VHB tape or any other strong double sided tape, mount the power supply to the underside of your cabinet,
Note: The yellow safety cover should protect you or any adult from being shocked by the power supply, but if there is any risk of small children getting access you should mount the power supply in an electrical box then mount the electrical box under your cabinet!
Step 19: Enjoy Your New Lights!!!
Here is another before and after. You can see that the lights makes a huge difference!
One nice thing about these is they are only 12 VDC and you can handle them with no risk of being shocked as long as you use a fully isolated power supply. If your lights tend to pull down from your cabinets you can even use hot glue to re-attach!