LED Driver (5 LEDs)




Posted in TechnologyElectronics

Introduction: LED Driver (5 LEDs)

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
Laser Printer
Glossy Paper

Step 1: Build It

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.



    • Microcontroller Contest

      Microcontroller Contest
    • Woodworking Contest

      Woodworking Contest
    • Casting Contest

      Casting Contest

    We have a be nice policy.
    Please be positive and constructive.




    7812 needs more than 14V input so output with 12v input will be about 10V

    2 replies

    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

    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

    Could you post a schematic picture, I'm confused