Instructables

LED Driver (5 LEDs)

Picture of LED Driver (5 LEDs)
SCH.jpg

This is a simple LED driver/power supply for 5 LEDs. Parts:
It uses the LM7812 positive voltage regulator,
2x 0.1uF Capacitors
1000uF/16V Capacitor
RBV - 406 rectifier
5 LEDs (I used transparent green)
A 12V transformer ~500mA
For Typical Forward Voltage use 78 - 100 ohms resistor for Max Forward Voltage use 15-30 ohms resistor
Spark Design PCB: http://designspark.com/page/designspark-pcb-home-page
Misc:
PCB
Laser Printer
Glossy Paper
Solder/Iron
Tools
.etc
 
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Step 1: Build it

Picture of Build it
DSCF0736.JPG
1) Print the schematic on glossy paper and use toner transfer method. (Print only Board Outline and Bottom Copper Side)
2) Etch
3) Remove toner
4) Acquire components and solder them as showed in schematic
5) Solder power cord to primary wire windings and connect the transformer
6) Measure for shorts and insulate primary wires, check the polarity of Electrolytic capacitor and LEDs and check the rectifier and 7812

Step 2: Use it

Use it for keyboard illumination or give a glow to a drink and have fun!
Find a box to put it in if you want and/or add a switch.
Sorry for grammar mistakes or something like that :D.
tutdude981 year ago
7812 needs more than 14V input so output with 12v input will be about 10V
Mock5 (author)  tutdude981 year ago
For a full-wave rectifier, the DC output will be 1.414 times the AC output. So the output of rectifier will be about 16V.
thats peak value
With some load it would be 12V - 1.3V (voltage drop from 2 diodes) = 10.7V and if you put that on 7812 youl get approx. 9V
Ploopy1 year ago
Where did you get the transformer?
Mock5 (author)  Ploopy1 year ago
Here in romania I get it from here : http://www.mivarom.ro/catalog/index.php/transformatoare-retea-c-199?osCsid=1jltjl0e4qbktqkkglf46m1nq4
It is a 12V 800mA transformer
Ploopy1 year ago
Thanks
Ploopy1 year ago
Cool!
Ploopy1 year ago
Could you post a schematic picture, I'm confused