How to construct a simple 5v dc power supply

How to construct a simple 5v dc power supply

Simple Microcontroller 5V DC Regulated Power Supply

Figure 1: Simple Regulated 5V DC Power supply circuit diagram

In any electronic product or project there is always a need for a source of power for the system to work. This is called a power supply.

The source of this power can come from different sources like the mains AC voltage, a battery or even from a renewable power source like a solar panel or fuel cell to name just a few.

The most common source of power is usually the mains AC, with this power, we need a transformer to convert the 220V 50Hz mains or the 120V 60Hz if you are living in the United States of America to a lower voltage required by the electronic circuit, this can be typically between 6V and 12V when 5V regulated DC is needed.
We are not going into the theoretical details here, I am going to discuss in this article only the basics for you to be able to build a simple power supply to power your microcontroller.
Here are the main components in this project:

  • Transformer
  • Diodes
  • Capacitors and
  • Voltage regulator

1. Power Source

The first thing to choose is the power source, this can be 220V AC mains stepped down with a transformer or we can use a 9V battery or even a solar panel depending on our application.
For our 7805 voltage regulator IC to work properly, it’s input voltage should be at least 2V greater than the required output voltage.
In this case as we are using a 5V regulator (5V required at the output), the input voltage should be close to at least 7V.
A 6V transformer with current rating of 500mA (since 6*√2 = 8.48V) can be used or any other power source supplying more than 7V like a 9V battery, solar panel etc.
Notes:

  • Any transformer which can supply a secondary peak voltage of up to 35V can be used with this 7805 voltage regulator but as the voltage increases as is the power dissipation across the regulator which may require a heat sink if there is a huge power dissipation.
  • For a portable devices, a 9V battery can be used, this will decrease the cost as they will be no need to use the diode rectifiers.

2. Rectifying circuit

The purpose of a bridge rectifier is to convert the stepped down AC voltage into a DC (direct current) voltage. The bridge rectifier is composed of diodes D1 to D4 offering a full wave rectification.

1N4004 diodes are used as they are capable of withstanding a higher reverse voltage of 400V and a forward current of 1A. These specifications are enough for this application, the 1N4001 and 1N4007 diodes can also be used.

3. 7805 Voltage Regulator

The 78xx (sometimes prefixed by some letters like: L78xx, LM78xx, MC78xx…) series is a family of fixed linear voltage regulator integrated circuits. These regulators are commonly used in electronic circuits requiring a regulated power supply due to their simplicity. They are easy to use, they require very few additional components (2 capacitors) and they are not expensive.
In this family, the xx replaces two digits, these digits indicates the output voltage, for example the 7805 has a 5 volt regulated output voltage while the 7812 has 12 volts, the 7815 produces 15 volts and so on.
The 78xx series are positive voltage regulators, this simply means that they produce a voltage that is positive relative to a common ground in contrast to the related 79xx series which are negative voltage regulators.
If a positive and a negative regulated voltage is required, the 78xx and 79xx ICs can be used together in the same circuit.

Figure 2: The 7805 regulator connection

Figure 2 above shows the connection of a 7805 regulator extracted from the 7805 datasheet, only two additional capacitors are required, the datasheet prescribes to use a 0.1μF capacitor at the output side to avoid transient changes in the voltages due to changes in load and a 0.33μF at the input side of regulator to avoid ripples if the filtering is far away from regulator.

In the circuit diagram on figure 1, 100μF capacitor is used at the input side to avoid ripples.
Rating:

This is the 5V 3A power supply circuit for those who want to have the Microcontroller or power digital supply source.

For use in experiments such as logic circuit and/or Microprocessor types or even raspberry-pi. These require 5 volts at high current up to 3A rate.

How to construct a simple 5v dc power supply

Due to this circuit is very simple with the LM323K (or LM123 or LM223) only one. But the can supply 5V fixed output voltage, and can be connected load current up to 3 Amp.

If you not can buy this IC or want an easy circuit with LM350 or 7805 more transistor.

Please read down.

There are 3 circuits that interesting.

Using LM323K

How it works

As shown in the circuit below. We will see that use LM323K only one.

How to construct a simple 5v dc power supply

Microprocessor 5V 3A power supply circuit using LM323K

Here is step by step a process.
In the circuit, there are only a few pieces of equipment. Such as. The transformer acts to reduce the voltage from AC main (230V or 117V as your country) to AC 9V.

Then, The bridge diode of 4A 100V converts the AC voltage into a DC voltage. Next, we use C1 as the current filter smoothly. And after, the IC1-LM323K regulator will maintain a constant voltage of 5 volts.

In addition, the internal circuit overload protection. Due to Short Circuit output and the thermal protection system over determine as well.

The C2 is a noise frequency filter. The C3 is the output filter.

Figure 2: the PCB layout

The parts list

IC1: LM323K or LM323T (To-220) THREE-TERMINAL 3A-5V POSITIVE VOLTAGE REGULATORS
C1: 4,700uF 16V Electrolytic capacitor
C2: 0.1uF 63V Polyester Capacitor
C3: 470uF 16V Electrolytic capacitor
T1: Transformer primary 9V at 3A.
BD1: Bridge diode 4A 200V.

Building

All equipment according to the circuit. Except the transformer can be mounted on the PCB is shown in Figure 2. In installing the IC1, be careful not to input or an output short circuit with the heat sink is strictly prohibited.

Using LM350 as 5V 3A regulator

Many people say that they can’t find LM323. I think we can use LM350 instead, but only need to modify a few additional devices. See the circuit diagram below.

How to construct a simple 5v dc power supply

5V 3A power supply circuit using LM350T

How it works

This circuit uses more equipment. Working on the unregulated power supply is similar to the circuit above.

But we added 3 filter capacitors in parallel Resulting in combined capacitance is 6,600uF. According to the original principles, choose capacitances 2,200 uF per 1A output current.

We should do this because it is cheaper than buying 10,000 uF and it’s easy to find too.

See LM350 Regulator. Normally, we can adjust the output voltage of 1.25V to 30V. And we can set this voltage by R1 and R2.

When we want 5V output, we should use R1 = 270 ohms, R2 = 820 ohms. Why I know it. Because I read…

Recommended: How to use LM350 Regulator

Diode protection

As datasheet, we should add both diodes to protect the backward voltage from the output and others. It can kill LM350.

Transient noise filter

C4, C7 (0.01uF to 0.1uF) filter out the transient noise which can be induced into the supply by stray magnetic fields. C5 and C6 keep the stable voltage.

LED1 is power on display like other circuits.

Parts lists

IC1: LM350 Three-Terminal 3A Positive voltage regulator
Electrolytic capacitor
C1-C3: 2,200uF 16V
C5: 22uF 16V Electrolytic
C6: 100uF 16V Electrolytic
C4,C7: 0.01uF 50V Polyester Capacitor
0.5W Resistor tolerance: 5%
R1: 270 ohms
R2: 820 ohms
Others
T1: Transformer, Primary 9V at 3A.
BD1: Bridge diode 4A 200V.

Using 7805 and PNP transistor (cheapest)

If you cannot by both LM323 and LM350. You can use normal IC-7805 and power transistors to make a 5V 4A power supply circuit.
It may be the cheapest circuit.

How it works

We intend to design this circuit to be smaller for saving.

How to construct a simple 5v dc power supply5V 3A Power supply using 7805 and TIP2955

The circuit is similar to the circuit above. Here is step-by-step a process.

In the unregulated power supply. We use it as a full-wave diode rectifier. In the circuit like this, we need to use a center-tap transformer, 9V-CT-9V.

As usual, we know that 7805 is a 1A 5V regulator IC. It runs great. But too low current for us. We need a helper that be kind.

So, the PNP power transistor, TIP2955 will boost up the current to 4A max. When the current flow R1. At B-E of Q1 get a bias current. It conducts current more than IC.

Overvoltage protection

But this circuit has a disadvantage is without overvoltage protection and short circuit protection.

This problem can be easily and effectively solved with fuse and Zener diode.

Fuse Easy but sure

Normally, we do not connect a short circuit or use an overcurrent. Using just one fuse is economical. Definitely works better than complex electronic circuits.

Zener over-voltage protection
We have learned that When the voltage reaches the VZ of Zener diode, it will have a lot of current flowing through it. If we use a 5.6V Zener diode and the voltage exceeds 5.6V.

This is the safe voltage level of the digital circuit. There will be a lot of current causing the fuse burns to immediately

Parts lists

IC1: LM7805, 3 Terminal 1A Positive voltage regulator
Q1: TIP2955, 15A 80V PNP transistor
ZD1: 5.6V 1W Zener Diode
Electrolytic capacitor
C1-C3: 2,200uF 16V
C4: 10uF 16V Electrolytic
C5: 100uF 16V Electrolytic
C6: 0.1uF 50V Polyester Capacitor
R1: 3.3 ohms, 1W Resistor tolerance 5%
Others
T1: Transformer, Primary 9V at 3A.
BD1: Bridge diode 4A 200V.
F2: 4A Fuse
F1: 1A Fuse

Do you try the OP-AMP Linear IC? They need to use the positive and negative power supply.

For example, +15V Ground -15V.

We can adjust the DC voltage with +5V to +25V and -5V to -25V at current 1 amp, using LM7805 and LM7905.

Introducing

If you want the Simple Dual Variable power supply circuit. I recommend making this circuit. Because it is easy. Use the integrated circuit 7805 Regulator and IC 7905.

Make have Voltage +5V to +25V and -5V to -25V unless.

VR1 for Adjustable + Volt output, VR2 for adjustable -volt output.

This circuit can provide current get about 1A enough with general usability.

The important factor is you should use a Transformer at enough size doesn’t lower 2A and IC all stick let off the heat with.

The DC power supply that has the positive voltage output and negative all in one form, and also can fine output voltage that need much in experiments the Linear ICs, especially op-amp.

Therefore, this power supplies so it is necessary on the experiments table all of those electronic players. Or will be used in the laboratory by various educational institutions. The need is not so bad. Saving money does not need to buy the foreign trade balance.

The building is easy, because the IC regulator 3-pin, Popular Numbers 7805 and 7905 controlled positive voltage and negative voltage respectively, by adjustable output voltage can be between from 5 to 25 volts, both positive and negative independently. Okay, let’s see how it works.

SEE image: 5 volt power supply circuit

How it works
This circuit is shown below.

How to construct a simple 5v dc power supply

-The transformer-T1 converts voltage AC 220V(or 120V for friends in the USA) reduce to DC 25V.The diodes D1 through D4 will rectifier the voltage from ACV to DCV. The Both positive and negative voltage flow to mix with 0V point or center taps of T1.

Then, the DC pulse will flow to 2 capacitors C1, C2 to filter the current, that is smooth up.
Next, 3 capacitors C3, C4, and C8 will protect a oscillated between IC1 and IC2

Next, the main of the circuit, is two IC1 and IC2 are dc regulator form 3 pin number IC-7805 and IC-7905. Which will be regulated to DC current output are +5 volt and -5 volts respectively.

When we put VR1 and VR2 into middle leg of IC1 and IC2 to adjust the output voltage.
The diode D5, D6 as act to Prevent the voltage from external backward into ICs, which it may be damaged.

For example the voltage from external large capacitors etc. but if there is the bad voltage in this circuit, it will flow through D5, D6 until the end and D7, D8 likewise.

When you want to change the voltage higher than 5V, simply adjust the VR1 and VR2, the higher the value the more resistance, the output voltage will increase as well.

How to construct a simple 5v dc power supply

LM317 LM337 Dual power supply Start 0V

How to build it

This project uses a few electronic parts and detail. I think that we can solder all equipment onto the perforated board.

You should put a low on their devices, such as diodes, resistors etc, then put them up high.

You may mount the VR1 and VR2 on the face of this power supply to easy the voltage adjustment.

We should mount the IC1 and IC2 on the heat sink to aid cooling. Be careful about the polarity of the circuit, capacitors, and diodes to correct place.

Because the DC regulator IC is a high current 1 ampere. Therefore, using the wiring the circuit, so it should be larger than 0.5 square millimeters. To minimize voltage loss in the cable, which will take place on the current lot.

The box of this dc power supply, you can use any plastic box, large enough to contain it, to get comfortable. The terminals output 3-pole connector is the positive, negative and ground terminals.

If you want to adjust both positive and negative changes to the VR1 and VR2 together it is variable resistor has a second layer using the same.

Bring it to use
When it is ready, then try to see what voltage changes or not. By adjusting VR1 and VR2 in the direction with the lowest resistance. Then, we measure output voltage need is +5 V and -5V. Next, Adjust in the opposite direction to the highest resistance. The output voltage will up to of 25V or highest.

You may mark voltage levels on the face completely. You should use a transformer at full current (2A up) because it is the heart.

For some people who want to the circuit easier.

Here is the circuit DC Power supply Adjustable Voltage 5V to 22V 1A by IC 7805.
It easy to make circuits and low cost too.

Power supply form the basic building block of any electronic circuits and therefore its important to familiarize the DC power supply circuit construction. The above given circuit illustrates a simple approach to construct a dual DC power supply of 5V and 12V from the 230V AC mains supply. The Voltage ranges 5V and 12V are widely used in all kinds of simple electronic circuits, so its meaningful to learn this simple construction.

WORKING OF DUAL POWER SUPPLY CIRCUIT:

The above circuit obtains power from a 230V AC mains supply voltage and fed into a step down transformer for transforming higher voltage supply to lower one. The transformer TR1 can be of 230V primary ,15V secondary and 1A step down transformer. The stepped down voltage can be fed into the bridge rectifier made of four 1N4004 diodes for the conversion of AC supply to DC one.

How to construct a simple 5v dc power supply
IC regulator pinout

The output from the bridge rectifier was filtered by the capacitor C1 and C2 to offer a steady DC level to the input pins of the regulators used in the above circuit. The DC voltage is then fed in to the IC 7805 which is a 5V regulator and also to the IC 7812 which was a 12V regulator. The output obtained from the 7805 & 7012 are 5V and 12V respectively. A LED D5 was connected through the current limiting resistor R1 for indicate the state of the device.

This kind of circuits are highly useful where two dual range of DC voltages are used to power the operation of a circuit. Varying the voltage regulator IC ‘s 7805 or 7812 with 7806 and 7808 to obtain 6V and 8V as output. But each IC have minimum and maximum voltage requirements, so make sure you build in such a way to meet the requirements.

Analog circuits often need a split-voltage power supply to achieve a virtual ground at the output of an amplifier. These split-voltage power supplies are generally low power supplies supporting tens of milliamps of differential current loads. Figure 1 shows such a power supply using two LTC3388-3 20V high efficiency step-down regulators powered from a 6V–12V power source.

How to construct a simple 5v dc power supply

Figure 1. Easy split-voltage power supply.

The positive voltage rail is created by configuring one LTC3388-3 in its standard buck topology while the negative voltage rail is created with a second LTC3388-3 by grounding the VOUT connection and using the GND pin as the negative voltage rail. The negative voltage rail is connected to the exposed pad of this LTC3388-3 and must be isolated from the system ground plane and have sufficient surface area to provide adequate cooling of the LTC3388-3.

The LTC3388-1 and LTC3388-3 are high efficiency step-down regulators that draw only 720nA (typ) of DC current at no load while maintaining output regulation. They are capable of supplying up to 50mA of load current and contain an accurate undervoltage lockout (UVLO) feature to maintain a low quiescent current when the input is below 2.3V. The output voltage is digitally programmable to four output regulated voltages along with a PGOOD status pin that indicates that the outputs are above 92% (typ) of the output setting. The LTC3388-1 can be digitally set to 1.2V, 1.5V, 1.8V or 2.5V while the LTC3388-3 can be set to 2.8V, 3.0V, 3.3V or 5.0V. Both devices are available in a 10-lead MSE or a 3mm × 3mm DFN package.

Operation of the Split-Voltage Supply

Configuring the LTC3388 as a buck regulator creates a positive voltage by ramping the inductor current up to IPEAK (150mA typ) through an internal PMOS switch and then ramping the current down to 0mA through an internal NMOS switch. This action charges the output capacitor to slightly above the regulation voltage at which time the buck regulator enters sleep mode.

As the output voltage decays due to an external load, the buck regulator remains in sleep mode and an internal sleep comparator monitors the output voltage. When the output voltage drops below the regulation voltage, the buck regulator wakes up and the cycle repeats. This hysteretic method of providing a regulated output reduces losses associated with MOSFET switching and maintains an output voltage at light loads. The buck regulator is able to support 50mA of average load current when it is switching.

A negative output voltage rail is created by grounding the VOUT node of the buck regulator. This sets the ground reference connection of the LTC3388 as a negative voltage rail. The voltage from the VIN pin to the negative voltage rail is the sum of the input voltage plus the magnitude of negative voltage rail. This limits the source voltage to 20V (the LTC3388’s VIN(MAX)) minus the magnitude of the negative rail voltage.

The inductor current is ramped up to IPEAK through the internal PMOS switch as in the buck regulator configuration and then down to zero through the NMOS switch, charging the output capacitor to a negative voltage. This switching action is that of an inverting critical conduction synchronous buck-boost converter. The maximum output current of this configuration is limited by the peak current of the inductor, the input voltage and the magnitude of the output voltage. The expression below estimates the maximum output current available.

In a split voltage power supply application, the analog circuit is connected between the positive voltage rail and the negative voltage rail. This results in the load current of both regulators to be equal in magnitude. Figure 2 is a plot of the input current versus the output current for the circuit in Figure 1. At very low load currents, <10μA, the effect of the input quiescent current can be seen as a positive offset in the input current. For higher load currents, >100μA, this effect is minimal and the input current is approximately equal to the output current. The expression for the input current may be approximated as:

How to construct a simple 5v dc power supply

How to construct a simple 5v dc power supply

Figure 2. Input current versus output current for the split voltage power supply of Figure 1 (–5V curve also applies to –5V supply shown in Figure 3).

Negative Voltage Supply

Figure 3 shows the buck-boost configuration creating a negative output voltage rail. In this configuration the input voltage needs only be above the UVLO voltage of 2.5V (typ) to start the regulator. The –5V curve in Figure 2 applies here with a 12V input, as in the previous circuit.

How to construct a simple 5v dc power supply

Figure 3. Negative voltage power supply.

An easy-to-implement split-voltage power supply using the LTC3388 yields a low quiescent current, high efficiency solution for powering low current analog circuits that need a virtual ground output. The output voltage of each device is digitally programmable to four output voltages from 1.2V to 5.0V and will support a load current up to 50mA. Each regulator requires only four external capacitors and one inductor, covering minimal board real estate. A PGOOD status pin is provided to indicate when the output is within regulation. The LTC3388-1 and the LTC3388-3 are available in a 10-lead MSE or a 3mm × 3mm DFN package.

Author

How to construct a simple 5v dc power supply

Jim Drew joined Analog Devices Inc. as a Senior Applications Engineer at the company’s Boston, MA Design Center in 2007. He was responsible for application support of Application Specific Power ICs. His area of interest is power conditioning applications for solar power, energy harvesting, supercapacitor chargers and active battery balancing. Jim was a consulting engineer at EMC, Hewlett Packard, Compaq and Digital Equipment Corporation responsible for power system development. He has also been an Adjunct Professor of Electrical Engineering at the University of Massachusetts Lowell where he now teaches since his retirement in 2017. Jim received his BSEE and MSEE from Lowell Technical Institute, now the University of Massachusetts Lowell.

How to construct a simple 5v dc power supply

In any electronic products or projects there is always a source of power for the system to work. This is called a power supply.

The source of this power can come from different sources like the mains AC voltage, a battery or even from a renewable power source like a solar panel wind turbine or fuel cell to name just a few.

The most common source of power is usually the mains AC, with this power, we need a transformer to convert the 220V 50Hz mains or the 120V 60Hz if you are living in the United States of America to a lower voltage required by the electronic circuit, this can be typically between 6V and 12V when 5V regulated DC is needed.
We are not going into the theoretical details here, I am going to discuss in this article only the basics for you to be able to build a simple power supply to power your microcontroller.
Here are the main components in this project:

  • Transformer
  • Diodes
  • Capacitors and
  • Voltage regulator

1. Power Source

The first thing to choose is the power source, this can be 220V AC mains stepped down with a transformer or we can use a 9V battery or even a solar panel depending on our application.
For our 7805 voltage regulator IC to work properly, it’s input voltage should be at least 2V greater than the required output voltage.
In this case as we are using a 5V regulator (5V required at the output), the input voltage should be close to at least 7V.
A 6V transformer with current rating of 500mA (since 6*√2 = 8.48V) can be used or any other power source supplying more than 7V like a 9V battery, solar panel etc.
Notes:

  • Any transformer which can supply a secondary peak voltage of up to 35V can be used with this 7805 voltage regulator but as the voltage increases as is the power dissipation across the regulator which may require a heat sink if there is a huge power dissipation.
  • For a portable devices, a 9V battery can be used, this will decrease the cost as they will be no need to use the diode rectifiers.

2. Rectifying circuit

The purpose of a bridge rectifier is to convert the stepped down AC voltage into a DC (direct current) voltage. The bridge rectifier is composed of diodes D1 to D4 offering a full wave rectification.

1N4004 diodes are used as they are capable of withstanding a higher reverse voltage of 400V and a forward current of 1A. These specifications are enough for this application, the 1N4001 and 1N4007 diodes can also be used.

3. 7805 Voltage Regulator

The 78xx (sometimes prefixed by some letters like: L78xx, LM78xx, MC78xx…) series is a family of fixed linear voltage regulator integrated circuits. These regulators are commonly used in electronic circuits requiring a regulated power supply due to their simplicity. They are easy to use, they require very few additional components (2 capacitors) and they are not expensive.
In this family, the xx replaces two digits, these digits indicates the output voltage, for example the 7805 has a 5 volt regulated output voltage while the 7812 has 12 volts, the 7815 produces 15 volts and so on.
The 78xx series are positive voltage regulators, this simply means that they produce a voltage that is positive relative to a common ground in contrast to the related 79xx series which are negative voltage regulators.
If a positive and a negative regulated voltage is required, the 78xx and 79xx ICs can be used together in the same circuit.

How to construct a simple 5v dc power supply

Figure 2: The 7805 regulator connection

Figure 2 above shows the connection of a 7805 regulator extracted from the 7805 datasheet, only two additional capacitors are required, the datasheet prescribes to use a 0.1μF capacitor at the output side to avoid transient changes in the voltages due to changes in load and a 0.33μF at the input side of regulator to avoid ripples if the filtering is far away from regulator.

In the circuit diagram on figure 1, 100μF capacitor is used at the input side to avoid ripples.
Rating:

Introduction: How to Build a Power Supply for Electronics Hobby

How to construct a simple 5v dc power supply

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How to construct a simple 5v dc power supply

How to construct a simple 5v dc power supply

How to construct a simple 5v dc power supply

This power supply can be used by electronics hobbyists.

Materials:
PC Power Supply with Cord
3/8″ MDF Wood
On/Off Switch From Old Computer
1 Red LED
1 Green LED
6 Banana Jack Sockets
Heat Shrink Tubing
Plexiglass (Lexan)
Wood Screws

Drill Motor
Drimmel with metal cutting wheel
Wire Cutters
Soldering Iron and Solder
Color Laser Printer
Table Saw
Multimeter
Hot glue gun and glue

Step 1: Dissamble Old Power Supply

1. Find a PC power supply. It should be in working condition.

2. Remove the metal casing, don’t cut or unsolder any of the wires. CAUTION: do not open the case when plugged in unless you know what you’re doing. The capacitors may continue to have a high voltage charge even when unplugged. so don’t touch them and/or discharge them before doing so.

3. Make a note of which color wires go together. Naturally all like color wires will be tied together. But during inspection if you see two different colored wires connected to the same pin on a connector then this is important and you should make note of it. These type of connections are used to sense voltage levels in the power supply. So don’t mix this up. If you do there are guides online that will show which color wires go together. Its just easier to make a note and keep them the same from the start.

3. Cut the connectors off the wires. Leave the wires as long as possible.

4. Group wires of like color together, and use heat shrink tubing to keep them together. Strip the insulation from the ends of each wire.

The color code for the wires is: Red = +5V, Black = Ground (0V) , White = -5V terminal, Yellow = +12V terminal, Blue = -12V terminal, Orange = +3.3V terminal, Purple = +5V Standby (for standby LED and 180 to 220ohm current limit resistor, black on ground side of LED), Gray = power is on (for power LED and 180 to 220ohm current limit resistor), black on ground side of LED), and Green = Turn DC on (power switch, black on ground side of SPST switch). Brown = senses +3.3V and should be kept connected with orange wires, Pink = senses +5V and should be kept with red wires.

NOTE: Some power supplies have other voltage sense wires too. these are usually thinner than the main wires and are either the same color (but thinner) or brown or pink. These should remain connected as they are or the power supply will not turn on. Just make a note of how all the wires are connected to the connector pins prior to cutting off the connectors and don’t change this wiring.

5. When PC power supplies are not connected to a load they sometimes will not turn on (or remain on). therefore you will need a load resistor connected between red and black wires to provide a load big enough to keep the power supply on with nothing is connected to the jacks. This load should be about 10 ohm 10 watt resistor between DC ground and the +5V rail (red). Don’t forget to heat sink this resistor.

Step 2: Build Enclosure

Build a wood MDF enclosure. This basically is the same size as the metal case that was just removed. except there is more room inside for making wire connections to banana plugs and on/off switches.

Step 3: Dimensions of Enclosure

I have attached an AutoCAD DWG and PDF files contain part sizes.

The dimensions contained in these drawing show 4 decimal places. NO you don’t have to build this to those tolerances! I just forgot to format the numbers correctly.

In this post we try to understand how basic power supply circuit works and how to design regulated and unregulated power supply circuits.

UNREGULATED POWER SUPPLY

A single rail power supply is displayed in the diagram below. It has three distinct portions, the power transformer, the full wave bridge rectifier and the filter capacitor.

How to construct a simple 5v dc power supply

For security, the fuse needs to be set the live wire path to the transformer. The voltages offered are AC voltages measured in Volts RMS. This can be the similar “DC heating” voltage and it is comparable to 0.707Vp.

The output of the transformer is 6V RMS and this also could be the voltage level “on load”. Once the transformer is just not loaded this voltage might enhance by around 25%.

The variation amongst the loaded and unloaded output voltage is referred to as the “regulation” of the transformer. Transformers possess power ratings indicated with regards to VA. A 10VA transformer are able to supply 10 watts of power through its secondary output.

The AC voltage through the transformer secondary is full wave rectified through the diode bridge D1 to 4 after which filtered by capacitor C1. Without any load on the power supply the output (DC) voltage will probably be roughly 11V.

However when a resistive load is shown to it, the voltage falls and a ripple voltage shows up, this being a result of the load discharging the capacitor.

REGULATED POWER SUPPLY

Two transistors and a voltage reference enables you to produce a regulated power supply.

Transistor Q1 is employed as the power control element thus needs to be installed on a heat sink. Q2 delivers adverse feedback and thus allows to iron out any alterations at the output caused by varying load conditions or variants in the unregulated rail.

The circuit procedure is as follows. A current passes via Q2 and D5 and so creates a voltage of 5V1 around D5. The base of Q2 is attached to the output with a set of resistors, R2, 3, 4 and RV1.

How to construct a simple 5v dc power supply

If the output voltage increases, then more current will pass via Q2. This leads to the voltage at the base of Q1 to drop, which often decreases the voltage at the output.

Hence the output voltage is controlled. RV1 is utilized to create the output voltage to +9V. In case the wiper of RV1 need to unintentionally lift off, then the output voltage might immediately increase to that of the unregulated rail.

To avoid this R3 supplies a long lasting DC path to the base of Q2. Capacitor C2 aids you to enhance the regulation once the load conditions change quickly.