Portable 3.3V and 5V Regulator

Club Jameco Designed Kit

Description: Portable 3.3V and 5V Regulator
Difficulty: Beginner
Time Required: 0.5 hours depending on experience
Designer: Sam Thongrong

This beginner project will allow you to safely regulate voltage of any electronic or robot project using 3.3V or 5V. Its small footprint gives you the option of mounting it on top of a 9V or 4-AA battery holder.

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Build your own Portable 3.3V and 5V Regulator

Required tools and parts:

Solder (21-23 AWG is recommended.)
Desoldering pump
Wire Stripper
Diagonal Cutter
Needle-nose Pliers

Portable Regulator

9V Battery
Double-Sided Foam Tape
Standard Regulator 3.3 Volt 0.1A 3-Pin TO-92 Bulk
Vise or Helping Hand

Kit Includes:

Qty.	Description	Mfr. Part No.
1	Diode	1N4001
2	Capacitor, 100µF	100UF/16V 6X5
3	Header	22-11-2022
1	Red LED	UT6371-41-M1-R
1	Switch	G4050X-R
1	Battery Holder	BH-9V-A-R
1	Capacitor, 10µF	10UF/35V 5X5-R
1	Capacitor, 0.1µF	MOC100000/100-R
1	Regulator	LM78L05ACZ
1	Resistor,1KΩ	CF1/4W102JRC-10
1	PCB	—
1	Instructions	—

Step-by-Step Instructions

Step 1 - Solder the Polarized Capacitors (C2, C1 and C4)

Insert the C2 (10µF) capacitor into place. C2 is located between C1 and C4 (both are 100µF capacitors) in the middle of the PCB. C2, C1, and C4 capacitors are all polarized. Orientation matters! Place the longer lead (positive or anode) in the positive-marked (+) hole and place the shorter lead (negative or cathode) in the other hole. Solder and then use the wire cutters to clip off the excess leads near the solder joint. Repeat the step with the C1 and C4 (100µF).

Step 2 - Solder the 0.1µF (or 100nF) Capacitor (C3)

Insert 0.1µF (or 100nF) capacitor (C3) into its place on the top layer of the board (the side labeled in white silkscreen). C3 is a ceramic capacitor. It is not polarized so orientation doesn't matter. Put the component in place, solder and trim.

Note: 1 micro farad (µF) = 1000 nano farad (nF)

Step 3 - Solder the 1N4001 Diode (D1)

Diode D1 (1N4001) is polarized; note the orientation. 1N4001 is added to the circuitry to block current from flowing in the opposite direction. It will block current from negative voltages or from the DC power supply.

D1 is located next to the power switch. You will notice that on both the D1 component and the PCB there is a white stripe. Place the D1 to match the label on the PCB. Put the component in place, solder and trim.

Step 4 - Solder the 3mm LED (LED1)

There is only one LED on this PCB. LED1 (red) is an indicator of power supply. It is located next to the 2-pin male header near Vout. The LED is polarized; note the orientation. Place the longer lead (positive anode) in the positive-marked (+) hole. Solder and trim.

Step 5 - Solder R1 1K Resistor

Locate resistor R1 next to LED1. R1 resistor is 1KΩ coded Brown, Black, Red, and Gold (+/- 5% tolerance). Insert resistor R1 into place. Resistors are not polarized; orientation doesn't matter. Set the resistor into the vertical orientation according to the label. Solder and trim.

Step 6 - Solder the Voltage Regulators (IC1, and IC2)

There are two voltage regulators on the board -- 5V (IC1) and 3.3V (IC2). Both have the same TO-92 package type. There are three leads or pins on the TO-92 package. To identify the pins of TO-92 package, hold up the 5V regulator (IC1) or 3.3V regulator (IC2) with the flat surface of the regulator facing you. Pin 1 is "Output pin", located on the left. Pin 2 is "GND", located in the middle. And pin 3 is "Input pin", located on the right.

These regulators provide a steady reference voltage with the help of the capacitors that connect them. Put the components in place, solder and trim.

To assemble the voltage regulators, first identify the 5V regulator (IC1) with the value "LM78L05A" displayed on the flat surface (a magnifying glass might be helpful!). Insert the 5V regulator into place by matching the shape of the regulator to the shape on the label. Solder and trim.

Repeat the steps above to assemble the 3.3V (IC2) voltage regulator with the value "LM78L33" displayed on the flat surface of the component.

Step 7 - Solder the 2-pin Male Connectors

The 2-pin male headers have a plastic holder between both ends; one side is shorter than the other. Insert the short side of the 2-pin male connector toward the top layer of the PCB and secure it with masking tape. Turn the board over and mount the PCB in a vise or third-hand. Heat both the pad and the end lead for a couple of seconds with the solder iron, then apply solder.

Step 8 - Solder the On/Off Switch

The On/Off slide switch has the SPDT (Single Pole Double Throw) configuration. The switch has three "symmetric" leads or pins, and could be installed or assembled in any direction. Insert the switch into place on the corner of the board. The leads of the switch are short. To secure the switch, tape it to the PCB before turning it upside down. Solder and trim.

Step 9 - Solder the Battery Wires

The red wire goes to the hole (pad) marked "+" (positive) on the Vin port. The black wire goes to the hole marked "-" (negative) on the Vin port. Solder and trim.

Step 10 - Test the PCB!

Test the circuit on a clean area by laying the circuit on a clean sheet of paper. Insert the 9V battery into the battery holder. Slide the switch to the ON position and check to see if the red led lights up. If not, switch to OFF and inspect your work to make sure the components are soldered correctly.

If everything's OK, use a multimeter to measure the voltage on each output port. Start with the Vout port. You should get a reading very close to 9V (below or above).

Check the 5V output pins. You should get a value very close to 5V. If far over 5V (such as 7V), turn it off, remove the battery, and inspect your work, especially IC1 and capacitors C1 and C2 to see if they were installed correctly. Check the 3.3V output pins. You should get a value very close to 3.3V. If not, turn it off and inspect your work, especially IC2 and capacitor C4 to see if they were installed correctly.

About the designer

Sam Thongrong, an Electronic Visualization Artist dedicated to better living through electronics, enjoys working with robots and Legos. He earned an MFA in Electronics Visualization from University of Illinois, Chicago.

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