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Monster Media 1994 #1
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POWERSUP.TXT
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1993-11-07
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3KB
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85 lines
BUILDING A 12 VOLT POWER SUPPLY
Components:
▄▄▄▄▄▄▄▄▄▄
120v MOV
T1 18 volt @ 2 amp. transformer (Radio Shack # 273-1515)
BR1 Bridge rectifier, 4 Amp. @ 50 PIV (Radio Shack # 276-1146)
(You may substitute 4 rectifier diodes in bridge configuration)
C1 4700 µF @ 35 v. electrolytic capacitor (Radio Shack # 272-1022)
C2 1000 µF @ 25 v. electrolytic capacitor (Radio Shack # 272-1019)
C3 .1 µF @ 25 v. disc ceramic capacitor (Radio Shack # 272-135)
7812 voltage regulator (Radio Shack # 276-1660 assortment)
(optional, see note)
120 volt, 1 amp. fuse
3-wire line cord
sw DPST toggle switch
Jacks and connectors
Perf board or project board
Enclosure
┌───────────┐
│ │ 7812 12-volt VOLTAGE REGULATOR
└──┐ ° ┌──┘
┌──┘ └──┐
│ │
└┬─────────┬┘
│ │
│ 7812 │ front view
│ │
│ │ Pin 1 = input
└┬┬──┬┬─┬┬┘ Pin 3 = ground
││ ││ ││ Pin 2 = output
││ ││ ││
││ ││ ││
││ ││ ││
└┘ └┘ └┘
1 3 2
┌───────────────────┐
│ FULL WAVE │
│ Bridge Rectifier │ BR1
│ │
│+ AC -│
└╥─────╥─────╥─────╥┘
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
║ ║ ║ ║
╨ ╨ ╨ ╨
12-volt Power Supply schematic
switch T1
AC ──/──┬─▒▒─┐ ac + 1┌──────┐2
black │fuse )││(─┬─────────┬────┬─────┤ 7812 ├─────┬───────┬──────■+12v out
┌──┴──┐ )││( │ bridge │ │ └───┬──┘ │ │
┌----│ MOV │ )││( │rectifier│ ─┴─+ 3│ ─┴─+ ─┴─+
≡grn └──┬──┘ )││( │ │ ─┬─ C1 │ ─┬─ C2 ─┬─ C3
│ )││( │ BR1 │ │ │ │ │
AC ─────┴─────)││(─┴─────────┤- │ │ │ │
white ac └────┼─────────┴────────┴───────┴─────┐
≡ gnd ≡ gnd
▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄
Note: The 7812 regulator may be omitted if the unregulated output is approx.
in the 10 - 15 volt range. The filter caps ARE necessary.
Warning: Use all appropriate precautions around the 120v AC input when
testing with the power on. AC power line voltage is dangerous
and can be lethal! If you are a novice at this, get assistance
from an electronics technician or experienced hobbyist.