Power Supply Module Ver. 2

Here is Ver. 2 of my small Power Supply Module for hobbyist to use when powering small projects when experiment or creating a new design. Power Supply Module Ver. 2 measures 6 x 4 cm (2 1/4 x 1 1/2").

A new feature on this version of the power supply is that it can also provide 3.3 volts in addition to one of the other voltages, which are 5, 6, 9, or 12 volts. Previous version did not have 3.3 volts.

Another feature is multiple output pins, as there is now five pins for 5 volts, five pins for 3.3 volts, and ten pins for ground. Previous version had only a single pin for output power and a single pin for ground.

Output current is max 1 amp for for voltages of 5, 6, 9, or 12 volts, and 800 mA for 3.3 volts.

This would be a great project for those getting into using Arduino's (myself include) that need a small power supply to test circuits without needing to connect an Arduino every time. This would be a nice school project for an electronics class.

You should have basic soldering skills and be able to read schematics.

Parts:

Parts are listed in the order they are installed during the build.

The PCB gerber files and schematic can be found on my Proton drive here, and the PCB can be ordered from PCBWay here.

male headers pins, standard 2.54 pitch, and you have two choices here, you can use a 2x10P in a single color, or you can do as I did and use single row header pins, I used white 1x5P for 3.3 volts, red 1x5P for 5-12 volts, and black 1x10P for ground.

LM1117-3.3 voltage regulator, SOT-223 surface mount package, x1

10K 1/4 watt resistor 5%, x1

SR260 Schottky diode, x1

DIP-6 socket, x1

3mm LED, green, x1

SPDT mini slide switch with 3 pins, x1

100nF (104) monolithic capacitor, x2

10uF 25v tantalum capacitor, x2

PCB mount DC jack 5.5x2.1mm, x1

10uF 25v electrolytic capacitor, x2

nylon standoffs 3x6mm, x4 plus 3mm screws, x4

LM78xx voltage regulators, 5, 6, 9, or 12 volts, with heatsinks, as needed.

15 volt 2 amp power adaptor (wall wart), with + on center pin.

Tools:

Schematic

Electrical tape

Soldering iron & solder, plus liquid flux and solder wick if mistakes are made

Flush cutters

Breadboard or pin header soldering tool, used for installing the header pins

Multimeter with hook probes

Since there is a low number of parts for this project, assembly is straightforward.

The basic premise is you solder in parts from lowest profile to tallest, but in this case we have 1 surface mount component, so we will get that out of the way first so we have lots of room around it to work.

If you have never installed a surface mount component, rest easy, the part is large compared to some surface mount components which can be quite small. The part we are going to install first is the LM1117-3.3 voltage regulator, this part can be installed without any special tools and just a regular soldering iron is used.

When your iron is hot, apply a small amount of solder to one of the 3 smaller pads. Place the regulator on the pads and hold down with a small screw driver or tweezers, apply the iron to the foot on the pad with the solder and you will feel when the solder flows and the piece sits flat on the board. Now solder the other two small feet, reflow the first foot you soldered and finally solder the tab itself.

Now it is time to get the header pins installed and out of the way. Using a breadboard or pin header soldering tool, install the header pins into the breadboard or tool, with the long part of the pins downward into the breadboard, making sure you have the colored pins in the correct fashion so the pins will be in the correct position on the PCB. Place a single row of header pins on its side on the breadboard or tool, this is to keep the PCB flat on the pin headers. Now place the PCB, upside down, over and onto the header pins. Solder each end of each strip of pins, check to make sure they are flush with the PCB, and solder the rest of the pins.

The basic premise for the remaining parts is to insert a part, use a piece of tape to hold the part in place, solder, check the joint for solder on each side, remove tape, trim leads as needed, and move onto the next part.

Go ahead and bend the leads for the resistor and the diode, and solder those in place.

At this point you can install the standoffs to keep the module off your work surface.

Functions:

U3, is the 3.3 volt regulator, and you need at least 1 other regulator installed in U1 for U3 to be powered.

H1, are header pins for power and ground, five pins for 5-12 volts, five pins for 3.3 volts, and ten pins for ground.

R1, is the current limiting resistor for the power on LED, D1.

D2, prevents reverse polarity, this is a Schottky diode for low voltage drop. Pay attention to the polarity of D2 when installing.

Install parts as listed below, paying attention to the polarity of capacitors C1 and C4 which are electrolytic, as well as C5 and C6 which are tantalum capacitors. The tantalum capacitors were used per the datasheet for the LM1117-3.3 voltage regulator.

Functions:

U1, is a 6 pin DIP socket, the pins marked 1, 2, and 3 are used for a 78xx voltage regulator of your choice, which is 5, 6, 9, or 12 volts. The front of the regulator goes towards the 1 2 3 markings and if you have a heatsink attached, the heatsink will be towards the edge of the PCB.

D1, is the green power on indicator.

SW1, applies the 15 volts from the power adaptor to the regulator in U1, regulator U1 provides power to the 3.3 volt regulator.

C2, C3, are filter monolithic disc capacitors and is part of the filtering for the regulator in U1. C2 is on input to U1 and C3 is on the output.

C5, C6, are tantalum filtering capacitors (polarized), per the 3.3 volt regulator datasheet, for the 3.3 volt regulator. C5 is on input to U3 and C6 is on the output.

J1, provides 15 volts to the regulator in U1, keep in mind center pin is +.

C1, C4, are electrolytic capacitors (polarized) and are part of the filtering for the regulator in U1. C1 is on input to U1, and C4 is on output.

For testing, I used a 7805 regulator inserted into U1, connected hook probes from my meter, and turned on the module.

First photo shows 5.053 volts on the 7805 regulator. And second photo I connected the positive from the meter to a 3.3 volt pin and it shows 3.307 volts on the LM1117-3.3 regulator.