In this How-To we show you how you can easily assemble a laboratory power supply. We decided to use a programmable control voltage module with constant voltage and constant current and install it in a suitable housing.
Suitable for: Beginners with basic knowledge
Time required: Approx. two hours
Budget: About £80
You will also need: Basic equipment of electronic tools, soldering station, etc.
1. Prepare a small circuit board
Starting with the small circuit board, solder a fan for the housing to this board. Then install a toggle switch and route a cable to the main board. Since this board has no connection for the fan, the fan for the case must be soldered to the small board.
Then, the cable of the supplied fan has to be cut. Now you must carefully remove the insulation from the two wires so that the wires are approx. 4mm free.
Solder the red cable (+) to the “+” marking and the black cable to the “-” marking. Insert the previously stripped ends through the holes and solder them from both sides.
Attention: Cut off these wires on the rear side with a side cutter so that they cannot cause a short circuit later!
2. Solder the pushbutton
Next, the button must be soldered so that the laboratory power supply can be switched on and off. Use the red and the black cable with the smaller diameter. Solder them to the toggle switch as shown in the picture.
The contacts are insulated with shrink tubing to prevent short circuits.
3. Establish connection between small board and main board
Now prepare and solder the supply line from the small board to the main board.
Use the cables (the red “+” cable and the black “-” cable) with a larger diameter for this supply line. Cut them off after a length of approx. 9cm.
Attention: Do not cut too many cables, otherwise the cables may become to short for the outputs later.
Both sides must be stripped to approx. 5mm and a forked cable lug must be attached to one end of the two cables. These ends are also insulated with shrink tubing to prevent a short circuit.
The other end of the two cables must be soldered to the small circuit board of the housing.
Pay attention to the polarity. Red = “+” and Black = “-“.
4. Solder the toggle switch
Now you can solder the toggle switch. Make sure that you lead the cable of the switch through the housing or attach the toggle switch to the housing. Solder the ends of the toggle switch cable to the “KEY” pads on the small circuit board. Solder the red cable to the rectangular pad and the black cable to the round pad.
5. Install the main board
Now you can fix the main board with four screws on the bottom side of the housing and install the connections of the inputs and outputs of the power supply. There are two connectors on the front and two on the back.
Screw the red connectors at the top and the black connectors at the bottom. Mount the connections as follows:
6. Prepare the cable for the output voltage
The next step is to make the cable for the output voltage. You will need to reuse the cables with the larger diameter. Strip both ends by approx. 5mm. Attach a forked cable lug on both sides.
7. Mount the fan
Now you can fix the fan from the inside by inserting four nuts from the back into the fan and fixing four screws from the outside to the fan.
8. Connect circuit board and switch
Now fasten the small circuit board to the back of the housing with two nuts.
Fix the small board is fixed then mount all the cables. First, attach the input voltage cable (“IN+” and “IN-“).
Next, you can attach the output voltage cable (“OUT+” and “OUT-“).
Connect the end of the output voltage cable to the front terminals.
9. Connect the display
The last thing you need to connect is the display with two cables on the motherboard. One cable is for the display (“LCD”) and one cable for the buttons (“KEY”). The connectors for the cables are marked both on the board and on the display. Once you have connected the cables, all you need to do is attach the display to the case.
10. Final assembly
Once you have connected all cables, screwed the circuit boards, snapped in the display and the toggle switch and screwed the fan, the case is complete.
You can now screw the case together with four screws on both sides.