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BREADBOARD PLUGIN POWER SUPPLY # 400039 REV3 +5VDC
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Learn Power Supply Design with a hands on approach
General Information and Features
Assembled Picture of the Breadboard plug-in power supply
Parts List of the Breadboard plug-in power supply
Unassembled Picture of the Breadboard plug-in power supply
Assembly Instruction
Schematic with blocking diode or fuse added for REV3
Explanation of Operation and New Features
MC78XX Spec that explains the heart of the power supply
LEARN POWER SUPPLY DESIGN
Build this kit and learn Power Supply Design and Operation.
Use this Power Supply with your breadboards to design and build circuit prototypes and then test.
The 7805 is the most common Power Supply out there. A lot of the devices you have utilize this Power
Supply design. As long as you are prototyping circuits on a breadboard you can use this Power Supply.
GENERAL INFORMATION
If you prototype circuits you will truly appreciate having a few of these breadboard Power Supplies to
compliment your prototyping environment.
If you are new to linear Power Supplies you will find this kit very hands-on and educational. It will help
develop your assembly and soldering skills followed by a good understanding of how linear Power
Supplies work.
For the more experienced it will provide power to numerous future designs to come. Prototypes are
normally the first step to a final design. Prototyping is just part of the design process. When you have
the appropriate breadboard adapters and power supplies you spend more time prototyping and testing the
actual circuit instead of focusing on the actual cable and power supply hookups.
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FEATURES
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Multiple Power Supplies can be used with multiple breadboards. It creates an excellent
prototyping environment allowing your main heavy duty lab Power Supply to be used on the
high current loads.
Low Cost…very affordable to have multiple units with various voltages
Very small, compact and will fit right on the breadboard for easy storage
Uses the 78XX series regulator. The most common regulator out there.
Multiple Voltages available 5-6-8-9-12-15-18-24 vdc.
A fuse can be added to create an independently fused Power Supply for custom applications.
A blocking diode has been added to protect the input from reverse polarity at hookup.
LED designate Output Voltage ON.
Allows you to utilize some of those DC wallwart Power Supplies that you have laying
around. There is always an overabundance of these. Give them a new life by recycling them
into your new test fixturing.
Provide an in depth understanding of Power Supply design.
Easy to assemble and solder. It just takes a few minutes
Easy connect/disconnect to a walwart with a 2.1mm coaxial socket.
Easy connect/disconnect to the breadboards.
It plugs into the breadboard power distribution strips on both sides.
Short circuit protection built into 78XX regulators
Easy to follow, step by step assembly instructions.
Detailed linear Power Supply operations tutorial.
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400039 ASM INSTRUCTIONS
1. Lay out all the parts like in the unassembled assy picture to ensure that you have all the parts
readily available for assembly.
2. Insert the LED D2 with the longer lead into the square ? pad hole. Spread legs and solder.
3. Insert diode D1 with the line closest to the center of the PCB.
4. Insert caps C3 and C4 , tack and solder.
5. Install the 2.1mm wall wart socket. Bend the tabs outward to flatten for minimized height and
solder the smaller side of the three tabs.
6. Install both large 1000uf caps with the longest lead into the square ? pad hole. Solder and trim.
7. Install the resistor R1 for the LED upright then solder and trim.
8. Install the 78XX regulator. Various Manufacturers can be used. Vertically mount to the 220 type
regulator high enough that you can still bend the regulator back 90 degrees to add a heatsink if
necessary.
9. Install the 1x2 connectors from the bottom of the PCB so that you can solder them from the top.
Ensure that you have installed it flush and 90 degrees to the PCB. This will insure easy and
correct installation of the Power Supply assembly into the breadboard power strips. If it is not
straight it might not install correctly.
10. INSTALLATION TIP When installing a part only solder tack one side of the part and then
inspect that it is positioned properly. Adjust if necessary at this point. The appearance of the
Power Supply is a reflection of your soldering/assembly ability. You will be using these Power
Supplies as long as you are breadboarding.
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EXPLANATION OF OPERATION AND FEATURES
The 78XX type voltage regulator is the most commonly used voltage regulator in the world. The newer
version of the LM78XX is the LM340. The 78XX series comes in a variety of voltages - +5Vdc 6Vdc
8Vdc 9Vdc 12Vdc 15Vdc 18Vdc and +24 Vdc. The part body type is called TO-220 and has a metal
heatsink on the back of the tab. An additional heatsink can be added to this for additional heat
dissipation for maximum specified current applications. There are probably a minimum of 40 different
manufacturers of this part. Detailed spec sheets are available from the different manufacturers for
current rating and voltage drop. These two numbers will allow you to calculate the power dissipation
with various current and voltage inputs. The higher the voltage drop and the higher the amperage equals
a higher power dissipation for the regulator. P = V x I It’s that simple.
BASIC CIRCUIT OPERAITON
The center positive 2.1mm wall wart supplies an unregulated +dc voltage to pin 1 of the 2.1mm PCB
connector. A 5mm 1x2 screw terminal (optional) can be installed if the Power Supply is not being used
as a breadboard power supply and it is being used as a custom supply. The optimum DC input should be
about 2-3 volts above the desired output voltage. The addition of the 1 amp optional fuse or diode is
new to revision rev 3 of this PCB. The diode can prevent reverse voltage damage from using a center
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negative wall wart and applying a reverse voltage. When selecting a wall wart examine the wall wart
label for voltage and current raging; AC or DC (DC required) and the 2.1mm configuration (center +).
Most wall warts are fused. The most common wallwart plugs are 2.1mm,2.5mm and 1.3mm. If the
power supply is to be used with an unfused DC input for a custom application, then a round 1 amp fuse
can be installed instead of the diode. This then creates a well regulated fused DC supply.
The large 1000uf CAP tries to maintain a constant DC voltage at the voltage regulator input. The small
.1uf CAP shunt to ground any high speed transients (fast voltage spikes or noise) that are approaching
the voltage regular input. The regulator maintains the specified voltage output by dissipating the voltage
above the desired output voltage. The more voltage and current dissipated means the more heat
generated. This is an extremely important concept to understand for Power Supply operation. Heat is
the biggest problem a Power Supply has.
The large 1000uf CAP on the output acts like a large battery to smooth output demand. The .1uf CAP
helps filter any switching noise or device transients that are present.
When the circuitry is working and the specified output is present ;the LED is on. The LED drops about
1.8 volts across it, leaving 3.2 volts across the dropping resistor. 3.2 volts divided by the 470 ohm
resistor is 6.8m A going thru the LED lighting it dimly. 20m A is full max current for this LED
operation. Maximum brightness is not a requirement in this application. The 2 1x2 pin on the bottom of
the PCB supply the regulated voltage and ground to both sides of the breadboard. Because of the size of
the PCB multiple different voltage supplies can be used when multiple breadboards are attached
together. A vary typical setup would be 3 breadboards snapped together with 2 Power Supplies. (one
+5Vdc One +12Vdc)
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