                   BUILDING A 12 VOLT POWER SUPPLY 

Components:
----------

120 v MOV
T1    18 volt @ 2 amp. transformer    (Radio Shack # 273-1515)
BR1   Bridge rectifier, 4 Amp. @ 50 PIV (Radio Shack # 276-1146)
C1    4700 F  @ 35 v. electrolytic capacitor   (Radio Shack # 272-1022)
C2    1000 F  @ 25 v. electrolytic capacitor   (Radio Shack # 272-1019)
C3    .1 F @ 25 v. disc ceramic capacitor      (Radio Shack # 272-135)
7812 voltage regulator                    (Radio Shack # 276-1660 assortment)
120 volt, 1 amp. fuse
3-wire line cord
sw     DPST toggle switch
Jacks and connectors
Perf board or project board
Enclosure

Ŀ          
                       7812 12-volt VOLTAGE REGULATOR
Ŀ    
     Ŀ
            

          
   7812                 front view
          
                       Pin 1 = input
              Pin 3 = ground
                   Pin 2 = output
     
     
     
     
  1   3   2 

 
 

Ŀ
     FULL WAVE     
 Bridge Rectifier     BR1
                   
+       AC        -

                
                
                
                
                

 





12-volt Power Supply schematic


     sw  fuse  T1                       
AC __/ıĿ    ac         +         1Ŀ2
             )(Ĵ 7812 +12v out
grn  Ŀ  )(  bridge                       
---  mov   )( rectifier   +      3       +    +
      )(              C1             C2    C3
             )(    BR1                               
AC __/)(Ĵ-                           
    sw            ac         Ŀ
                                                                   gnd
                                                                   
