Sunday, August 22, 2021

PinOut - ARDUINO Mega Rev3 Board - ATMega328PU

Fig. 1- Arduino Mega Rev3 Board - arduino.cc

The Arduino Mega 2560 is a microcontroller board based on the ATmega2560. It has 54 digital input/output pins (of which 15 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button.

Click here to Arduino Datasheet

Source: arduino.cc

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Monday, August 9, 2021

How to Make Cable; Guitar, Keyboard, Bass, Audio Mix, PA, among others, Step by Step!

How To Make Cable of, Guitar, Bass, Audio Mix, PA, and some others Quality!



Today we bring you a quick guide on how to build your own audio cable for: Musical Instruments, Home Studio, Soundboard, Amplifiers, Automotive Sound, Recording Studio, Professional Sound, Microphone Cable, Balanced Cables, CD Player, among so many others.

You might also be interested in:


There is a huge variety of cables, but we will show the most common ones, which, as they are the most common, are the most used.

This article is part of another article from our partner fvm learning, you can visit them by clicking on the address link: fvml.com.br 

We will start with the most common and we will advance as far as possible:

1° It's a Cable: A mono P10 Male connector to a mono P10 Male connector

This type of cable is one of the most eclectic, and most of it is used between musical instruments, such as keyboards, bass guitars, guitars, and so on. and the audio mix, to carry a signal to the PA "Public Audition", among others. This is shown in Figure 1 below.

Fig. 1- Diagram Mono P10 Male to P10 Male Connector

2° It's a Cable: One male P10 stereo connector to two male P10 mono connectors

This type of cable is generally used between the mixer and the effect module, using the insert channels to send and receive effects, among many others. This is shown in Figure 2 below.

Fig. 2- Diagram P10 Male Stereo Connector for Two Mono P10 Male Connector

3° It's a Cable: One Balanced Female XLR Connector for Two Mono P10 Male Connectors

These types of cables are generally used in audio mix connections to balanced amplifiers among other myriad uses. This is shown in Figure 3 below.

Fig. 3- Female XLR Connector Diagram for 2 Mono P10 Male Connectors

4° It's a Cable: A Balanced Female XLR Connector to a Male P10 Stereo Connector

This cable is generally used to connect a Power Play "Headphone Amplifier Distributor" to the Soundboard auxiliary, we can also connect to a balanced microphone "When available on the audio mix with Plug P10" with Microphone powered with Phantom Power, between so many others. This is shown in Figure 4 below.

Fig. 4 - Female XLR Connector Diagram to a Male P10 Stereo Connector

5° Is a Cable: One XLR Female connector to one P10 mono Male connector

This cable is generally used to connect a microphone to the mixer, and or to connect the output of the XLR console to the amplifiers, among many others. This is shown in Figure 5 below.


Fig. 5 - Diagrama  Conector XLR Fêmea para P10 Macho Mono

6° It's a Cable: One Male Balanced XLR connector to two P10 mono Male connectors

This type of cable is generally used to connect the output of the mix to P10, L and R, for active box, amplifiers, which has a stereo XLR input, among others. This is shown in Figure 6 below.


Fig. 6 - XLR Male Connector Diagram for 2 P10 Mono Male

7° It's a Cable: One Balanced Male XLR Connector to One Male P10 Stereo Connector

This type of cable is generally used to connect a balanced signal from equipment, to a mix, such as instruments with low sensitivities, such as; "depending on the model" Guitar, ukulele, among others. This is shown in Figure 7 below.

Fig. 7 - XLR Male Connector Diagram for P10 Stereo Male 

8° It's a Cable: One XLR Male connector to one P10 mono Male connector

This type of cable is similar to the previous one, except that it is used for unbalanced signals, for a mix, such as instruments with low sensitivities, such as; "depending on the model" Violão, Cavaquinho, among others. This is shown in Figure 8 below.
Fig. 8 - Male Unbalanced XLR Connector Diagram for P10 Mono Male

9° It's a Cable: A Balanced Female XLR connector to a Balanced Male XLR connector

This cable is well known and standard for use in balanced Microphones, but it is also widely used to connect peripherals such as; equalizers, processors, effects equipment to the Mix, as well as to connect the output of the XLR console to the Active Box, Amplifiers, among many others. This is shown in Figure 9 below.


Fig. 9 - Balanced XLR Connector Diagram Male Balanced XLR

10° It's a Cable: Two RCA Male connectors to one P10 Stereo Male Connector

This type of cable is generally used for connecting P10 stereo output signals to loudspeakers that have RCA inputs, among many others. This is shown in Figure 10 below.

Fig. 10 - Diagram Male RCA Connector to Male P10 Stereo Connector

11° It's a Cable: Two male RCA connectors to two P10 mono Male connectors

This type of cable is generally used to connect output signals from the Mix, usually the older ones, with P10 connectors for amplifiers that have signal inputs with RCA connectors, also used to connect CD, DVD, Disc and other peripheral devices to the line input on the soundboard, among others. This is shown in Figure 11 below.

Fig. 11 - Diagrama Conector RCA Macho para Conector P10 mono Macho

12° It's a Cable: Two RCA Male Connectors to Two RCA Male Connectors

This type of cable is generally used to connect the Mix's auxiliary output signals, usually the older ones, with RCA connectors for amplifiers that have the signal inputs with RCA connectors, also used to connect CD, DVD, Disc and other devices. peripherals to the auxiliary RCA input on the mixer, among others. This is shown in Figure 12 below.



Fig. 12 - RCA Male Connector to Male RCA Connector Diagram


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Wednesday, August 4, 2021

Symmetrical Adjustable Power Supply 1.25V to 47V 10 Amps with Short Circuit Protection + PCB


Fig. 1 - Symmetrical Adjustable Power Supply 1.25V to 47V 10 Amps with Short Circuit Protection  
This is a Symmetrical Adjustable Power Supply can vary its output voltage from 1.25V to 47V, based on the LM317HV Linear Voltage Regulator Integrated Circuit for positive voltage and the LM337HV for negative voltage, which together with the NPN transistors TIP 35C and the PNP transistor TIP36C provide a current of 10 amps.

This schematic was taken from our partner fvml.com.br, what we did was a small change in the supported current capacitance, you can check the original circuit here Click Here!

High Voltage Adjustable Regulator

The LM317HV and LM337HV voltage regulators are adjustable 3-terminal voltage regulators capable of delivering currents of 1.5A or more over an output voltage range of 1.25V to 50V

The LM317HV and LM337HV offer overload protection such as current limiting, thermal overload protection, and safe-area protection, that make the device breakdown-proof. The overload protection circuit remains fully functional even if the setting terminal is disconnected.

Remember, we limit the maximum output voltage of the power supply to 47V, because the LM337HV negative voltage regulator supports a maximum of 50V, unlike the LM317HV which supports up to 60V.

How the Circuit Works

After rectification and filtering, which are the first basic operations of the circuit, the total voltage coming from the transformer and rectified enters the first output block, the voltage regulator, which is controlled by the LMs Integrated Circuit and mirror image "Same function, just in a negative way".

R1 and R2 are 10 ohm resistors that have the function of Load Sensor, they receive the current flowing through the circuit, and while this current does not reach the current calculated across the resistors R1 and R2, the circuit behaves like a normal voltage regulator, because for small "calculated" currents there is no voltage drop across the Load Sensing resistor, so the Boosters Transistors TIP36C and TIP35C are not activated.

When the current in the circuit increases, the voltage across resistor R1 increases, when this voltage reaches about 0.6V "transistor turn-off voltage", the power stage is activated and current flows through it.

The Protection Circuit

The output short circuit protection circuit is formed by transistors; Q1 BD140 PNP and Q2 BD139 NPN, each for an output bias voltage.

They regulate the maximum current "Calculated", which is fixed at 10 amps, and work together with 0.06ohm resistors R3 and R4 as a current sensing resistor, which is used to polarize transistors Q1 and Q2, so that, depending on the determined value, they limit the output current of the entire circuit according to a simple formula from Ohms Law, which is used to set this limiting current.

Formula 1st Ohm's Law

The First Ohm's Law states that the potential difference between two points of a resistor is proportional to the electrical current established in it, and the ratio of electrical potential to electrical current is always constant for ohmic resistors. The formula is given by: V = R * I

V - Voltage or Electrical Potential
R - Electrical Resistance
I - Electrical Current

Armed with the knowledge of the ohms law, we can now calculate the values ​​of the Load Sense resistors, which activates the power step, and the bias resistors of the protection transistors, which is the Short Circuit protection circuit.

Load Resistor Calculation

First, we have to know the current of the LM317hv Voltage Regulator, which according to the datasheet is 1.5 amps.

LM317HV & LM337HV = 1.5A
Let's calculate R1, knowing that the same calculation is done for R2. We know that Ohm's Law gives us the following expression:

V = R * I
V = The cutoff voltage of transistors Q3, Q4 & Q5, which follows the same principle for set Q6, Q7 & Q8, is 0.6V "Which is the Transistor cutoff region". Let's call Q3, Q4 & Q5 as a Qeq.

I = It is the current of the regulator CI1, let's put the working current of the CI1 at 300mA, which is equal to 0.3A, with this current we won't need to put a heatsink on it.

Then:

R1 = Vbe_Qeq / I_CI1
R1 = 0.6V / 0.3A
R1 = 2 ohms

Protection Circuit Resistor Calculation

Likewise, we have to know the total current of the chosen source so that there is a cut in this region. Our source is for 10 Amps.

Power Supply = 10A
Let's calculate R3, knowing that the same calculation is done for R4. We know that Ohm's Law gives us the following expression:

V = R * I
V = The cutoff voltage of transistor Q1, which follows the same principle as for transistor Q2, is 0.6V "Which is the Transistor cutoff region".

I = It is the total current of PS, which is 10A.

Then:

R1 = Vbe_Q1 / I_ps
R1 = 0.6V / 10A
R1 = 0.06 ohms

Power Transistors Current

Q3 + Q4 + Q5 = 25A + 25A + 25 = 75A

NOTE: Remembering that the power of TIP36C transistors is 125W, this means that it works with current from 25A to 5V, remember the formula above, P=V*I;

P = 5V * 25A = 125W.

For this circuit with a maximum voltage of 47V, and transistors with a maximum power of 125W, we look like this:

Pmax = V * I:
Imax = P / V => Imax = 125W / 47V => Imax = 2.66A
How are three transistors together Imax = 7.98A

And that's why our circuit uses three TIP36C transistors to achieve 10 amps at the output.

In Figure 2 we have the schematic diagram of the adjustable power supply circuit with short circuit protection, so those who accompany us already know this circuit very well, the difference is exactly the implantation of the symmetry of the circuit and the protection circuit, as we can see below.
Fig. 2 - Symmetrical Adjustable Power Supply 1.25V to 47V 10 Amps with Short Circuit Protection

The Power Transformer

The transformer must be symmetrical, i.e.: "3 wires". The transformer must be able to supply at least 10A at the output. The primary, "input voltage", must match the voltage in your area; 110V or 220Vac. The secondary, "output voltage" should be 36 - 0V - 36Vac.

Component List

  • Semiconductors
    • U1 ....................... LM317HV Voltage Regulator 
    • U2 ....................... LM337HV Voltage Regulator 
    • Q1 ....................... PNP BD140 Transistor 
    • Q2 ....................... NPN BD139 Transistor 
    • Q3, Q4, Q5 ......... PNP TIP36C Power Transistor
    • Q6, Q7, Q8 ......... NPN TIP35C Power Transistor 
    • D1 ...................... KBPC5010 - 50A Rectifier Bridge
    • D2, D3 ............... 1N4007 Diode Rectifier 

  • Resistors
    • R1, R2 ................ 2Ω / 2W  Resistor 
    • R3, R4 ................  0.06Ω / 5W Resistor 
    • R5, R6 ................ 5KΩ  / 1/8W Resistor 
    • R7, R8 ................ 120Ω / 1/8W Resistor 
    • R9, R10, R11 ...... 0.1Ω / 5W Resistor 
    • R12, R13, R14 .... 0.1Ω / 5W Resistor 
    • RV1 .................... 5KΩ Potentiometer 

  • Capacitors
    • C1, C2 ................ 5600uF - 63V Electrolytic capacitor 
    • C3, C4 ................ 10uF - 63V Electrolytic capacitor 
    • C5, C6 ................ 1000uF - 63V Electrolytic Capacitor

  • Others
    • P1, P2 ................. Connector 3 screw terminal 5mm 3 Pins
    • Others ................. Wires, Solders, pcb, etc.

We offer for download the necessary materials for those who want to assemble with PCI - Printed Circuit Board, the files in PNG, PDF and GERBER files for those who want to send for printing.

Download:


If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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Thursday, July 15, 2021

3.7V Li-Ion Battery Charger Circuit using MCP73831 IC + PCB

Fig.1 - 3.7V Li-Ion Battery Charger Circuit with IC MCP73831


The  MCP73831  device  is an advanced  linear charge  management  controllers  for  use  in  space limited, cost-sensitive applications. 

The MCP73831 is available in an 8-Lead, 2 mm x 3 mm DFN package or a  5-LeadSOT23  package.

Along  with  their  small physical size, the low number of external components required make the MCP73831 ideally suited for portable  applications.  

For  applications  charging  from  a USB   port,   the   MCP73831   adhere   to   all   the specifications governing the USB power bus.

The MCP73831 employ a constant-current and constant-voltage charge algorithm with selectable preconditioning  and  charge  termination.  

The  constant  voltage regulation  is  fixed  with  four  available  options:  4.20V, 4.35V,  4.40V  or  4.50V,  to  accommodate  new,  emerging  battery  charging  requirements. The  constant  current  value   is   set   with   one   external   resistor. 
The MCP73831 device  limit  the  charge  current  based on die temperature during high power or high ambient conditions.   

This   thermal   regulation   optimizes   the charge cycle time while maintaining device reliability. Several  options  are  available  for  the  preconditioning threshold, preconditioning current value, charge termination  value  and  automatic  recharge  threshold.  

The preconditioning  value  and  charge  termination  value are set  as  a  ratio,  or  percentage,  of  the  programmed constant  current  value.  

The  MCP73831  device  is fully a specified  over  the ambient temperature range of -40°C to +85°C.

The Circuit

The circuit is very simple and uses few external components which facilitates the assembly and reduces the assembly cost, the standard charging voltage regulation is normally set at 4.2V

However, there are variations in the nomenclature of the last digit of the IC that differentiate them from the standard charging voltage, such as:
  • MCP73831-2 = 4.2V
  • MCP73831-3 = 4.3V
  • MCP73831-4 = 4.4V
  • MCP73831-5 = 4.5V
The constant current charging value, is adjusted through resistor 2.2K ohms R3, which in our circuit is programmed for a ~450mA charge. Using a simple formula, we can vary this constant charging current:
Rc = charging resistor
CC = charging current in mA

Formula:
Cc = 1000/Rc

Being our 2.2K resistor, we have:
Cc = 1000/2.2
Cc = ~ 450mA

Remembering that the minimum charging current for this device is 15mA and the maximum current is 500mA.

Lithium-ion Batteries have become popular in large scale in portable electronic devices, due to them having higher energy density compared to other batteries on the market.

Benefits include thousands of recharges and none of the old, well-known “memory effect” problems we had in the first rechargeable NiCd battery cells

However, lithium-ion batteries must be charged following a carefully controlled constant current (CC) and constant voltage (CV) pattern that is unique to this type of cell.

Overloading and careless handling of a Li-Ion cell can cause permanent damage or instability and a potential danger of explosion.

In Figure 2 below, we have the 3.7V Li-Ion Battery Charger Circuit schematic diagram, with the MCP73831 IC and we can follow and analyze the entire circuit, which is a simple and easy-to-assemble circuit, with few external components.
Fig. 2 - 3.7V Li-Ion Battery Charger Circuit with IC MCP73831

Features

  • Linear load management controller:
  • Integrated pass-through transistor
  • Integrated current direction
  • Reverse Discharge Protection
  • High precision preset voltage regulation: +0.75%
  • Four voltage regulation options: 4.20V, 4.35V, 4.40V, 4.50V
  • Programmable load current: 15 mA to 500 mA
  • Selectable preconditioning: 10%, 20%, 40% or Disable
  • Selectable end of charge control: 5%, 7.5%, 10% or 20%
  • Three-state status output - MCP73831
  • automatic shutdown
  • Thermal regulation
  • Temperature range: -40°C to +85°C
  • Packaging: 5 derivations, SOT-23
  • applications
  • Lithium Ion / Lithium Polymer Battery Chargers
  • Personal Data Assistants
  • Mobile phones
  • Digital cameras
  • MP3 Players
  • Bluetooth Headphones
  • USB chargers

Components List

  • U1 ...................... Integrated Circuit MCP73831
  • LED1 ................. Light Emitting Diode - Red
  • LED2 ................. Light Emitting Diode - Green
  • R1, R2 ............... 240 Ohm Resistors
  • R3 ...................... 2.2K Ohms Charging Program
  • Others ................ Wires, connectors, PCI, tin etc.

The PCB - Printed Circuit Board

We are offering the PCB, in GERBER, PDF and PNG files, for you who want to do the most optimized assembly, either at home.

If you prefer in a company that develops the board, you can is downloading and make the files in the Download option below.

Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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Friday, July 9, 2021

How to Read Ceramic and Polyester Capacitors Correctly

Fig. 1 - Various capacitors - how to read correctly


Due to many manufacturers and various norms and standards established nowadays, many acronyms are implemented in electronic components and use a wide variety of codes to describe their characteristics, which makes them difficult to read, there is an intrinsic coding to indicate the capacitors values, and manufacturers use different methods.

Sometimes generating a bit of confusion, some indications such as; tolerance and also the working supply voltage often aren't clearly written on them.

Will explain how to read the capacitors, identifying: microfarads (μF), nanofarards (nF), picofarads (pF), tolerance, voltage, and so on.

For values ​​equal greater than 1000nF (eg with aluminum or tantalum electrolytics), they mostly write the value on the body followed by the abbreviation for microfarad (μF).

For values ​​less than 1μF (1 microfarad), the issue is not so clear.
Generally, an encoding consisting of a three-digit number followed by a letter is used.

Before the most skeptics and purists come to question this Post, let us clarify that the correct abbreviation for microfarad is the Greek symbol; micro (μ). Which is a prefix of the International System of Units denoting a factor of 10−6 (one millionth).

Confirmed in 1960, the prefix comes from the Greek; μικρός (transliterated: mikros), meaning small. Followed by the capital letter F.

Usually when we're doing component descriptions, we don't always have the Greek symbols available on our keyboard, so to prevent this symbol from being wrongly transcribed, we substitute it for the lowercase letter "u", although we mustn't forget that we're always talking about the letter. "μ" (micro).

We have other cases, examples of this type, it is the symbol Ω (ohm) that is sometimes replaced by the letter "R" or, in some other cases nothing is written.

As mentioned at the beginning, with the exception of electrolytic capacitors that generally far exceed the value of 1 microfarad, the universe of capacitors used in electronics consists of capacitors with values ​​ranging from a few pF or picofarad (ceramic or disk capacitors look like lentils) to those close to 1 microfarad or 1μF (multi-layer polyester).

Before continuing, it is worth remembering "for whoever forgot" the subject of submultiples.

Submultiples

A pF (picofarad) is the smallest submultiple that exists to "practically" indicate capacity. I say practical because there are still smaller submultiples, SI Prefixes (International System of Units)

(deci, centi, milli, micro, nano, pico, femto, atto, zepto and yocto), but they are not used in electronics. 1 picofarad is 1,000,000 (1 million) times less than 1 microfarad (μF).

Halfway between picofarad and microfarad there is another sub-multiple called nanofarad widely used and it is 1000 times larger than 1 picofarad and 1000 times smaller than 1 microfarad.

Typical Capacitor Values

For capacitors facing between 1pF to 1μF (almost all capacitors except for electrolytic), reference values ​​are indicated with a three-digit number followed by a letter.

The first two digits indicate the starting number, while the third digit represents the number of zeros that must be added to the starting number to get the ending value. 

The result obtained is necessary to consider it in picofarad.

Examples of encodings

Let's use it as an example; 4 types of captions written on the capacitors, as shown in Figure 3 below.

In the capacitor in Figure 2, we can see in the description only a set of three numbers "104", which representing the capacitance in Picofarad reading.

Figure 2 - Capacitor with only capacitance captions



104 - Which is its capacitance in pF, and without any further information.





The capacitor in Figure 3, we can see in the description the set of 3 numbers "400" which representing the working voltage, followed by the letter "V", which is the working voltage indication, and the set of three numbers below "104", which represents the reading in Picofarad.

Figure 3 - Capacitor with voltage and
capacitance value captions


400V - Which is the working voltage.

104 - What is its value in pF






The capacitor in Figure 4, we can see in the description the set of 3 numbers "104", which represents the reading in Picofarad, followed by the letter "J", representing Tolerance, and the set of three numbers "250" represent the working voltage followed by the letter "V", which is the working voltage indication.

Figure 4 - Capacitor with capacitance, tolerance,
voltage captions 


104 - What is your capacitance in pF

J - It's the tolerance

250V - Is the working voltage.





The capacitor in Figure 5, we can see that in the description it starts with a number and a letter "2A" which represents the value of the maximum working voltage, then the set of 3 numbers "104", which represents the reading in Picofarad, followed by the letter "J" representing Tolerance.

Figure 5 - Capacitor with maximum voltage,
capacitance, tolerance 


2A - Which is the value of your maximum voltage

104 - What is your capacitance in pF

J - It's your tolerance





Let's Practice:

Let's say you have a capacitor with the nomenclature written "472", just as we take resistor readings, the third capacitor digit is also the multiplier, which means it would be: 47 + 2 zeros, which means 4700 pF (picofarad).

So if we exceed 1000 picofarad, we can use Sub-multiples, "like we do with meters/kilometers". As already clarified above that:

1μF = 1000nF
1nF = 1000pF

So, we can say that our 4700pF capacitor is 4.7nF.

In this case, it is not convenient to use the micro unit because the value would not be easy to read (0.0047μF).

With larger values, such as used capacitor filters number 104, that is, 10 + 4 = 100,000 pF or also 100nF, it is common for manufacturers to use the nomenclatures written on the capacitor body 0.1μF or .1μf (point one μF) .

Practical reading of the Polyester Capacitor

100nF Capacitor, tolerance of  ± 5% and maximum working voltage of 100V, Figure 5 above.

In this capacitor we have 6 alphanumeric digits, 2A104J.

  • The first two initial 2A digits refer to Maximum Voltage, we can use the complete EIA table codes that indicate the maximum capacitors work voltages in direct voltage (DC).

EIA Table of Code Indicators of Working Voltages of a Capacitor

0G = 4VDC0L = 5.5VDC0J = 6.3VDC
1A = 10VDC1C = 16VDC1E = 25VDC
1H = 50VDC1J = 63VDC1K = 80VDC
2A = 100VDC2Q = 110VDC2B = 125VDC
2C = 160VDC2Z = 180VDC2D = 200VDC
2P = 220VDC2E = 250VDC2F = 315VDC
2V = 350VDC2G = 400VDC2W = 450VDC
2H = 500VDC2J = 630VDC3A = 1000VDC

  • The next three digits refer to its capacitance, in the case as already exemplified 104 = 10 + 4 zeros, which is equal to 100,000pF = 100nF.

  • The last digit is the Letter "J", right after the three digits, determines the tolerance of the component.

    It is interesting to note the fact that some letters correspond to "asymmetric tolerances", such as "P", that is, the component may have a capacity greater than indicated, but not less.

    This type of tolerance is used with "filter" capacitors, where a value possibly higher than indicated does not minimize circuit operation, as we can see in the EIA table below.

EIA Table of Code Working Tolerance Indicators of a Capacitor

  • B = ± 0.10pF
  • C = ± 0.25pF
  • D = ± 0.5pF
  • E = ± 0.5%
  • F = ± 1%
  • G = ± 2%
  • H = ± 3%
  • J = ± 5%
  • K = ± 10%
  • M = ± 20%
  • N = ± 30%
  • P = ± +100%, - 0%
  • Z = ± +80%, - 20%
In the vast majority of cases, it may be useful to know the exact maximum voltage the capacitor can withstand without bursting or damaging its internal properties.

As we know, a capacitor is made up of a series of metal plates insulated from each other. This insulating material is very subtle, especially in the case of high-value capacitors. 

On the other hand, if the voltage is too high, there is a risk that an electrical arc will pass through the electrical insulation between the plates, breaking it and shorting the capacitor.

For this reason, the insulating material used is designed to work up to a certain maximum voltage level, so let's look at these capacitor voltages.

Dimensions of a Voltage-Based Capacitor

Often the maximum working voltage can be found clearly written, especially on capacitors designed to work with high voltages, other times the voltage value is not directly indicated.

It often happens with capacitors used in low voltage circuits. These capacitors support voltages between 50V and 100V, well above the typical working voltages of 5V, 12V, 18V, 24V, 48V.

A super important tip when designing or analyzing a circuit and not knowing for sure the capacitor working voltage, is to take into account the size, which in this case "size is important", as we cannot work with the structure of a capacitor. 

A high voltage and small size, of course there are exceptions, tantalum capacitors are altogether quite small compared to their capacitance, but as I said, "compared to their capacitance, not their voltage".

Last but not least, there is a numeric encoding used by some manufacturers which consists of a number followed by a letter. In the table of tolerances we can see the maximum working voltages.

As with everything related to technology, nothing is absolute and therefore a component manufacturer always appears, which uses systems to indicate values ​​different from those we describe. In any case, in general terms, this article's description fits very well (sometimes with slight variations) to most commercial capacitors nowadays.

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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My Best Regards!!!

Monday, June 21, 2021

68W Hi-Fi Audio Power Amplifier using LM3886T IC + PCB

Fig. 1 - PCB  68W Hi-Fi Audio Power Amplifier - IC LM3886T

The LM3886 is a high-performance audio power amplifier capable of delivering 68W of continuous average power to a load and 38W into with 0.1% THD+N from 20Hz–20kHz

The performance of the LM3886, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPiKe) protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area (SOA)

SPiKe protection means that these parts are completely safeguarded at the output against over-voltage, under-voltage, over-loads, including shorts to the supplies, thermal runaway, and instantaneous temperature peaks. The IC pinout is shown in Figure 2 below.
Fig. 2 - Pinout IC LM3886T

The LM3886 maintains an excellent signal-to-noise ratio of greater than 92dB with a typical low noise floor of 2.0μV. It exhibits extremely low THD+N values of 0.03% at the rated output into the rated load over the audio spectrum, and provides exceptional linearity with an IMD (SMPTE) typical rating of 0.004%.

Features

  • 68W cont. avg. output power into 4Ω at VCC = ±28V
  • 50W cont. avg. output power into 8Ω at VCC = ±35V
  • 38W cont. avg. output power into 8Ω at VCC = ±28V
  • 135W Instantaneous Peak Output Power Capability
  • Signal-to-Noise Ratio ≥ 92dB
  • An Input Mute Function
  • Output Protection from a Short to Ground or to the Supplies via Internal Current Limiting Circuitry
  • Output Over-Voltage Protection against Transients from Inductive Loads
  • Supply Under-Voltage Protection, not Allowing Internal Biasing to Occur when |VEE| + |VCC| ≤ 12V, thus Eliminating Turn-On and Turn-Off Transients
  • 11-Lead TO-220 Package

The Power Supply

The power supply is Symmetrical, for those who will use a 4Ω Loudspeaker, the 2x 20Vac transformer is recommended, because when rectified, it is around 28Vdc.

And for those who will use it at 8Ω, it is recommended the 2x 25Vac transformer, which when rectified, is 35Vdc on average.

The recommended transformer power is about 120W, this means that the transformer current is on average 3.5 Amperes, for mono, if it's stereo, do the duplication, that is, 8 Amperes. 

A good size heat radiator is necessary, since the IC LM3886 works in class AB, there is a great loss in heat at full power, and the recommended filter capacitors is 2 x 10.000uF/50V

The output inductance is formed by 15 turns of enameled wire, with a diameter of approximately 0.5mm, wound around the resistor R8 of 10Ω 1W. The complete schematic diagram is shown in Figure 3 below.
Fig. 3 - Schematic  68W Hi-Fi Audio Power Amplifier - IC LM3886T

Components List

  • U1 ..........................LM3886 Integrated Circuit
  • R1, R3 .................. 2.2K ohms - 1/8W - Resistor  - (red, red, red, gold)
  • R2, R4, R5, R6 ..... 47K ohms - 1/8W - Resistor  - (yellow, violet, orange, gold)
  • R7 ......................... 4R7 ohms - 1W - Resistor  - (yellow, violet, gold, gold)
  • R8 ......................... 10 ohms - 1W - Resistor  - (brown, black, brown, gold)
  • C1 ......................... 2.2uF - 25V - Electrolytic capacitor 
  • C2 ......................... 680pF Polyester capacitor 
  • C3 ......................... 470uF - 50V - Electrolytic capacitor 
  • C4, C8 .................. 100nF - ceramic/polyester capacitor
  • C5, C7 .................. 1000uF - 50V - Electrolytic capacitor
  • C6 ......................... 47pF - ceramic/polyester capacitor
  • C9 ......................... 220nF - ceramic/polyester capacitor
  • C10 ....................... 100uF - 50V - Electrolytic capacitor
  •  L1 ........................ 0.7uH Inductor - *See Text 
  • P1, P2 ................... Block 5mm 2 Pin weldable terminal Connector
  • P3 ......................... Block 5mm 3 Pin weldable terminal Connector
  • Others ................... PCP,  Heat Sink, Wires, Solders and Etc.

We are offering the PCI - Printed Circuit Board, in GERBER, PDF and PNG files, for you who want to do the most optimized assembly, either at home.

If you prefer in a company that develops the board, you can is downloading and make the files in the Download option below.

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