Download THE LM338 VARIABLE POWER SUPPLY MODULE/KIT By: www

THE LM338 VARIABLE POWER SUPPLY MODULE/KIT
By: www.engineeringshock.com
This module described here is based on the 5-Amp Adjustable Regulator LM338K, which is
capable of supplying in excess of 5A over a 1.2V to 32V output range. The power input of this
module can be AC 3-36V taken directly from a transformer. There is a rectifier bridge is on the
board. DC power input also can be applied directly through the board. Please see our
assembly video.
This module can generate between 1.2V – 30V DC at the output by adjusting the on board
variable resistor. It can provide 50W power and the cooling fan is used for cooling. Please note
the voltage of the power output should be lower at least 2 volts than the VRMS (Root Mean
Square) of the power input.
The fan will not work unless you have more than 12VDC after the rectifier. The fan requires
12VDC to operate, and there is an on-board 12v regulator that protects the fan.
LM338K Schematic
Notes:
LM338K Components List
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Reference
U1
U2
C3,C5,C7
C1
C2
C6
R18
W1
D1
D2,D3
CON1, CON2
Part Description
IC, LM7812
IC, LM338K
CAP 100nF，DIP
CAP 4700uF
CAP 2200uF
CAP, 10uF
RES, 220R,DIP,1/4W，1%
Potentiometer,5K
DIO，Rectifier bridge
DIO，1N4007，DIP
CON, 2PIN
Radiator
FAN
SCREW3
LM338K Layout
LM338K kits Assembly Guide
1. Mount the components with low profile
Mounted components:
1) CON1,CON2
2) W1: Potentiometer 5K
3) C3, C5,C7: 100nF
4) C6: 100uF
5) D2,D3: 1N4007
6) R18: 200Ohm, 1%, 1/4W
7) U1: LM7812 (Please bend the pin as shown in the picture before soldering)
The components for J1, C4 are not assembled and don’t care them.
2. Assembly the heat radiator and LM338K with two screws. Assembly the cooling Fan with
4 screws
TOP side:
Bottom Side
Note: Please add the pads when assembly the cooling FAN to avoid the short circuit.
3. Solder the power supply wires for cooling FAN, which provided by the 12V output on the
boards.
Connect the black wire from FAN to the hole marked with ‘G’ and the RED wire from FAN
to the hole with ‘12V’ on the board.
4. Assemble the C1,C2 and Rectifier bridge
Here, we assembly C1 with 4700uF and C2 with 2200uF