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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