Introduction: Variable Lab Bench Power Supply.
Bench power supplies are boxes that you plug into the wall, and provide an adjustable range of DC voltage on their output terminals. They usually have some knobs and a meter of some sort on them to help dial in the correct voltage. Some also have current limiting to help when troubleshooting or testing a new project. (Keeping the current limited to just above what the device needs can help prevent shorts from damaging components).
This is a fully adjustable bench power supply with Constant Voltage(CV) and Constant Current(CC) adjustments. To use, turn on the supply with the leads disconnected. Make sure the Current knob is not all the way down. Adjust the voltage knob to get the desired VDC on the display. Plug in your device. If the bottom CC light is on, that means it's in current limiting, and it's backing down the voltage to limit the current.
Output: Adjustable 1.3V to 19.5V
Max Adjustable current: 4.5 A
Short circuit protection: Yes (limit current 8A)
Overtemperature protection: (automatically shut off the output after overtemperature).
Input reverse polarity protection: No
Step 1: Materials :
Here is a list of materials I used for this project:
1 x XL4015 DC-DC STEP DOWN ADJUSTABLE MODULE
1 x VOLMETER AMMETER DISPLAY
1 x POWER SUPPLY 19.5V 4.55A (LAPTOP CHARGER)
2 x 10KΩ POTENTIOMETER
1 x LM7805 VOLTAGE REGULATOR
2 x KNOBS
1 x 4mm BANANA JACKS (RED + BLACK)
1 x4mm BANANA SOCKETS OR BINDING POST (RED + BLACK)
1 x SPDT SWITCH
1 x AC SPDT SWITCH
1 x USB FEMALE PORT
1 x CLOVERLEAF SOCKET OR 3-PIN SOCKET ( I SCRAPED FROM LAPTOP CHARGER)
CABLE ZIP TIES
SOME 3D CARBON FIBRE VIYNL WRAPS
Step 2: ModifIcation in the DC-DC Converter.
Remove the small two of potentiometer which are on the DC-DC module, and replace with two rotary potentiometer with ribbon cables.
One is for CC and the other one for CV.
Step 3: POWER SUPPLY:
For the power supply I have used an old LAPTOP CHARGER.
Remove the SMPS from the charger case. This SMPS is rated at 19.5v 4.55A total of 90W. Which is enough for this project. I also removed the cloverleaf jack from the charger itself.
Step 4: Schematic and Diagrams:
Refer to the diagram to connect all of parts together.
MAKE SURE YOU GROUND THE SMPS.
I forget ground in the scematic.
POSITIVE FROM SMPS TO IN+ OF CONVERTER AND RED WIRE OF VOLTMETER AMMETER DISPLAY. GROUND TO IN- OF CONVERTER AND BLACK WIRE OF VOLTMETER AMMETER DISPLAY.
YELLOW WIRE FROM VOLTMETER AMMETER TO OUT+ FROM CONVETER.
CONVERTER OUT- TO THICK BLACK WIRE OF THE DISPLAY.
THICK RED WIRE OF DISPLAY TO GROUND TERMINAL OF BINDING POST.
AGAIN OUT+ OF CONVERTER THROUGH A SPDT SWITCH TO POSTIVE TERMINAL OF BINDING POST AND INPUT OF LM7805 VOLTAGE CONVERTER FOR REGULATED+5V OUPUT THROUGH USB.
Voltmeter connects parallel and Ammeter in series.
The output connection wire should have a sufficient diameter to carry the desired current.
use heat shrink tubing for the connections and good amount of hot glue to lock things on place.
Step 5: Enclosure:
I have used a wooden box for this project with dimensions of 190mm x 60mm x 90mm (l x b x h).
For the front panel, first i marked the outline an by using simple tools like drill and hand saw.
6mm hole for the potentiometers and binding posts.
3mm holes for leds.
4mm hole for spdt switch.
Used BLACK MATTE PAINT for the body.
And last VINYL WRAPPED THE FRONT PANEL.
This is diy project, so.... its upto you how you design the enclosure. ;)
Do this as You comfort.
Step 6: Assemble Everything Into One Piece.
I LABEL" V " AND " A " ON THE FRONT PANEL USING NAIL PAINT.
Step 7: TESTING!
FOR THE REGULATED +5V OUTPUT FROM USB SET VOLTAGE TO ABOVE 5.2V.
FOR VARIABLE OUTPUT, OFF THE OUTPUT SWITCH, SET THE DESIRED VOLTAGE USING THE KNOB AND THEN SWITCH ON THE OUTPUT SWITCH.