Adjustable Power Supply 1.2V to 37V / 6A, with Short-Circuit Protection with LM317 and TIP36

Hello, electronics enthusiasts!

If you've worked with variable power supplies, you've probably encountered the classic regulators LM317 with a maximum current of 1.5A, and the LM350 with a maximum current of 3A. These components are true workhorses in electronics workshops.

However, as our projects become more demanding, the need for more current arises. This is where booster drivers come in - auxiliary circuits with power transistors that amplify the current capacity. But with great power comes great responsibility... and a big problem!

The answer is: YES, without proper protection, a short circuit can damage your expensive components. We could use fuses, but that would mean constantly replacing them, which is not practical at all!

That's why today we're presenting an elegant and effective solution: an Adjustable Power Supply with Short-Circuit Protection that combines the simplicity of the LM317 with the power of the TIP36C and the security of an intelligent protection circuit.

🛠️ The Electronic Circuit: An Overview

The heart of our project is a classic adjustable voltage regulator, the LM317. However, to achieve the impressive 6A mark, we've added two crucial stages:

Stage 1

• Regulation: LM317 Controls the output voltage with precision.

Stage 2

• Amplification: TIP36C (x2) "Booster" that provides the high current.

Stage 3

• Protection: BD140 "Guardian angel" against short circuits.

The differential of this project is not just in the power, but in the intelligence of the protection circuit, which uses a BD140 transistor in an ingenious way to protect the power transistors TIP36C against overloads.

💡 How the Circuit Works: The Detail That Makes the Difference

Let's unravel the magic behind this circuit. The operation can be divided into three key moments: normal operation, activation of the booster, and protection activation.

🔍 The Role of the Sense Resistor (R1)

The resistor R1 is the first "watcher" of our circuit. It works as a shunt resistor, that is, a current sensor. Think of it using a simple analogy:

While the output current is low (up to about 600mA), the "pressure" (voltage) across R1 is insignificant, and the circuit behaves like a common LM317 regulator.

⚡ The Magic of the Booster (TIP36C)

When you demand more current (above 600mA), the voltage across the terminals of R1 reaches approximately 0.6V. This value is magical in the world of transistors: it's the voltage needed to "turn on" a bipolar transistor.

Upon reaching 0.6V, R1 sends a signal to the TIP36C transistors (Q2 and Q3), which wake up and start working in parallel with the LM317, sharing the effort and allowing the circuit to deliver much higher currents, reaching the desired 6A.

🛡️ The Guardian Angel (BD140 and R2)

Now comes the most intelligent part. What happens if a short circuit occurs? The current would spike to dangerous values, destroying the TIP36Cs. This is where our hero comes in: the BD140 transistor (Q1) and its partner, the resistor R2.

The resistor R2 is another current sensor, but this one monitors the total current coming out of the power supply. It was calculated so that when the current reaches the safety limit (6A), the voltage across it also reaches 0.6V.

This protection mechanism is self-resetting. As soon as the short circuit is removed, the current returns to normal, the voltage across R2 drops below 0.6V, the BD140 turns off, and the TIP36Cs resume normal operation. No fuses to replace, no headaches!

🔬 The Science Behind the Magic: Ohm's First Law

All this elegant operation is based on one of the pillars of electricity: Ohm's First Law. This law describes the fundamental relationship between voltage (V), current (I), and resistance (R).

Where:

With this powerful mathematical tool, we can precisely calculate the value of the sense resistors (R1 and R2) to define when each stage of the circuit should be activated. Let's do the calculations!

🧮 Practical Calculations: Defining the Activation Points

Now that we understand the "why," let's get hands-on and do the calculations that ensure the perfect and safe operation of our power supply. Don't be intimidated, the math here is our ally!

ℹ️ Calculation of the Load Resistor (R1) - The Booster Trigger

Our goal with R1 is to tell the TIP36C transistors when it's time to enter action. We want this to happen before the poor LM317 starts to sweat.

Let's apply Ohm's Law:

Simple, isn't it? A 1 Ohm resistor is the perfect command to activate our power reinforcements.

ℹ️ Calculation of the Protection Resistor (R2) - The Bodyguard

Now, let's calculate R2, the component that saves the day. It needs to activate the BD140 exactly when the current reaches our design limit: 6A.

💪 Why Two TIP36C Transistors?

You might be wondering why we use two TIP36C transistors. The answer lies in their ability to dissipate power. A transistor is not just a switch; it also consumes energy in the form of heat.

The TIP36C supports up to 125W. But this maximum power is achieved under ideal conditions, generally with low voltage between collector and emitter. Let's see what the maximum current it can handle in the worst situation: with the maximum output voltage (37V).

Aha! A single TIP36C cannot deliver the 6A we need. But by connecting two in parallel, the current capacity is added:

🔌 Schematic Diagram: The Treasure Map

With all the theory and calculations in mind, let's visualize the complete circuit. In Figure 2, we have the schematic diagram. Try to identify the three stages we discussed: the LM317 regulator, the pair of TIP36C transistors, and the BD140 protector.

Fig. 2 - Schematic diagram of the Adjustable Power Supply circuit with short-circuit protection

🔗 Related Content

If you liked this project, you might also be interested in these other articles:

• Switched Power Supply SMPS 13.8V 10A using IR2153 IC and IRF840, with PCB
• Adjustable Power Supply 1.5V to 28V, 7.5 Amps With IC LT1083 + PCB
• Symmetrical Adjustable Power Supply 1.25V to 47V 10 Amps with Short Circuit Protection + PCB
• Adjustable Switching Power Supply 5.1 to 40V, 2.5 Amp using L4960 + PCB
• Adjustable Power Supply 1.2 to 37V High Current 20A with LM317 and TIP35C + PCB
• Adjustable Power Supply 1.25v to 57V, 6 Amps with TIP36C + LM317HV + PCB
• Adjustable Power Supply 1.25v to 33V, 3 Amps with LM350 + PCB
• Stabilized Power Supply 13.8V High Current 10 Amps with PCB

📋 Component List: Your Assembly Kit

To make your life easier, we've organized the list of materials in a clear table. Have everything at hand before you start soldering!

🖨️ The Printed Circuit Board (PCB): The Heart of the Project

A good schematic is the beginning, but a well-designed Printed Circuit Board (PCB) is what separates a project that works from one that is reliable and safe. For power circuits like this, the PCB layout is critical.

Figure 3 shows the PCB we prepared for you. It was optimized to facilitate assembly and ensure maximum performance and safety of your project.

Fig. 3 - PCB  Adjustable Power Supply 1.2V to 37V / 6A, Short-Circuit Protection  LM317 and TIP36

📥 Direct Link to Download Files

To download the necessary files for assembling the electronic circuit, just click on the direct link provided below:

Direct Link: PNG, PDF, GERBER Files

🛠️ Assembly Tips: The Secret to Success

Before you pick up the soldering iron, check out these golden tips. They can save a lot of time and avoid frustrations (and burned components!).

❓ Frequently Asked Questions (FAQ)

We've gathered some of the most common doubts about this project to help you assemble with even more confidence.

🎉 Conclusion: Your Ideal Bench Power Supply

And so we reach the end of this complete project! With this adjustable power supply, you have in your hands an extremely versatile (1.2V to 37V), powerful (6A) and, most importantly, safe tool, thanks to the short-circuit protection.

Whether for testing LEDs, powering microcontrollers, driving motors or for any other electronic adventure, this power supply will be your reliable partner on the workbench.

👋 I hope you enjoyed it!!!

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!!!

Fig. 1 - 5-Band Equalizer Circuit with LF353 IC

The LF353 is a two-input JFET operational amplifier with an internally compensated input offset voltage. The JFET input device provides wide bandwidth, low input bias currents and offset currents.

You might also be interested in:

• 3-Band Active Equalizer Circuit with LF353 IC + PCB
• 1W Amplifier for Stereo Headphone with IC TDA2822 + PCB
  
  

Features

• Internally trimmed compensated voltage: 10mV
• Low input bias current: 50pA
• Wide gain bandwidth: 4 MHz
• High slew rate: 13V / μs
• High input impedance: 1012Ω
  
  

The equalizer circuits

The Power Supply

The power supply used for this circuit is symmetric, i.e.: +15V | 0V | -15V, with a direct current voltage DC.

The recommended supply voltage ranges between ±11V and ±15V, but note that the maximum voltage supported by the IC is ±18V.

The consumption current of the IC is 6.5mA maximum and 3.6mA on average.

The Circuit

The 5-band Equalizer uses three Integrated Circuits operational amplifier LF353, and the capacitors determine the frequencies, the higher their capacitance, the lower the cutoff frequencies.

Each IC has two internal amplifiers, we get an amplifier for each frequency and the last one for the final amplification of the entire circuit. In Figure 2 below, the pinout and configuration of the LF353 integrated circuit is shown.

Fig. 2 - Pinout IC LF353

In Figure 3 below, we show the complete 5-band equalizer circuit, and that you can download the files in option; Download files below at the bottom of the page.

Fig. 3 - Schematic Diagram 5-band Equalizer Circuit with LF353 IC

Components List

• U1, U2, U3 .... LF353 Integrated circuit
  
  
• R1  ................. 47K resistor (yellow, purple, orange, gold)
• R2 to R11 ...... 10K resistor (brown, black, orange, gold)
• R12 ................ 100K resistor (brown,  black, yellow, gold)
  
  
• C1 ................... 680nF polyester capacitor
• C2, C3 ............ 150nF polyester capacitor 
• C4 ................... 33nF polyester capacitor
• C5 ................... 39nF polyester capacitor
• C6, C7 ............ 8.2nF polyester capacitor
• C8, C9 ............ 2.2nF polyester capacitor
• C10 ................. 470pF polyester capacitor
• C11 ................. 4.7uF electrolytic capacitor
  
  
• VR1 to VR5 ... 47K Potentiometer 
  
  
• P1  .................. Screw Terminal Type 5mm 3-Pin Connector
• P2, P3 ............. Screw Terminal Type 5mm 2-Pin Connector

• Others ............. PCB, tin, wires, etc.
  
  

Download

We provide the files with the PCB, the schematic, the PDF, GERBER and JPG, PNG and provide a direct link for free download and a direct link, "MEGA".

Click on the direct link to download the files: Layout PCB, PDF, GERBER, JPG

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

Subscribe to our blog!!! Click here - elcircuits.com!!!

My Best Regards!!!

Fig. 1 - Using LDR Sensor and reading values on Serial Monitor

Welcome to Lesson 8 - Basic Arduino Course

In today's lesson, we will learn how to use an LDR sensor and read values on a Serial Monitor with Arduino. 

To measure light intensity, we will use the famous and widely used low-cost LDR (Light Dependent Resistor) sensor, to detect the intensity of light or darkness easily and cheaply.

LDR (Light Dependent Resistor) Sensor

LDR is a special type of resistor that passes higher voltage (low resistance) when light intensity is high and low voltage (high resistance) when darkness is low. 

With this method, we can use it for example in projects such as:

• Lack of Light Alarm - Triggers an alarm when power is cut.
• Brightness Control - Used to control the brightness of a recording or filming environment for example.
• Contrast Control Screen - Often used on mobile phones to automatically lower or increase the brightness of the Display.
• Emergency Light - Automatically turns on when Light is cut.
• Ticket Counter - Also used to count people at the entrance of an establishment.
• Invasion Alarm - Used to trigger an alarm when there is an invasion of the monitored establishment. 

In today's example, we will use this sensor to measure numerical resistance and read these values from the serial monitor.

To do this, we will use the Arduino analog Port A0. We can use any analog Port, in case of Arduino Uno there are 6 ports; A0 to A5.

Hardware Required

• Arduino Board
  
• LDR - Sensor Dependent Light
• 100K ohms resistor - (Brown, black, yellow, gold)
• Jumper Wires
• Protoboard (optional)

The Circuit Connections

The circuit is very simple, we connect one leg of the LDR to positive 5V, and another leg to the 100K resistor in series with negative GND, and the same leg that takes the resistor and LDR, we connect to port A0, as shown in Figure 2 below.

Fig. 2 - Using LDR Sensor and reading values on Serial Monitor - tinkercad.com

We use a protoboard to facilitate the connections, but you can also connect the wires directly to the Arduino.

The Code

The analogReads() function, reads the value from the specified analog pin. Arduino boards contain a multichannel, 10-bit analog to digital converter. This means that it will map input voltages between 0 and the operating voltage(5V or 3.3V) into integer values between 0 and 1023. 

On an Arduino UNO, for example, this yields a resolution between readings of: 5 volts / 1024 units or, 0.0049 volts (4.9 mV) per unit

After building the circuit, connect your Arduino board to your computer, launch Arduino Software (IDE), copy the code below and paste it into your Arduino IDE. But first let us understand the code line by line. 

• In Line 3, we declared sensorPin to select the analog input Pin A0 to connect the LDR.
• In Line 4, we declared sensorValue as a variable to store the value coming from LDR sensor.
  
  
• In Line 6, we enter the void setup() function. This function is read only once when the Arduino is started.
• In Line 7, we sets the serial port for communication, we will read the numeric value from LDR sensor. 

• In Line 10, we enter in the loop() function does precisely what its name suggests, and loops consecutively.
  
  
• In Line 11, the sensorValue variable, receives the value read from sensorPin, which is the analog input Pin, and stores the read values.
  
  
• In Line 12, the Serial.println() function, prints the values from the variable sensorValue on the serial monitor screen.

The complete code is showed in the sketch below!

Complete 180W RMS 4-Channel Amplifier with TDA7386 PCB Design

The TDA7386 four-output integrated circuit is a Class AB amplifier rated at 180W RMS with "unbalanced power supply" in a single package with few external components. This makes it an ideal choice for both beginners and experienced electronics hobbyists looking to build a high-quality audio amplifier.

⚙️ TDA7386 Features: What Makes It Special?

🎯 Perfect Applications for Your TDA7386 Amplifier

Based on the TDA7386 IC, this amplifier is incredibly versatile. While it's designed for car audio systems, it's also ideal for:

Each channel of the TDA7386 provides 45W RMS with a sufficient power of 14.4 volts, at a load of 4 ohms and a distortion factor of about 10%. This means you get impressive volume with minimal distortion, perfect for both music and movie audio.

🔌 Amplifier Circuit Diagram: Understanding the Design

The amplifier schematic shown in Figure 2 is a simple design with few external components, making it an easy amplifier to build even for beginners. Let's break down the key components and their functions:

Fig. 2 - Complete 180W RMS 4-Channel Amplifier with TDA7386 Schematic

🧾 Complete Bill of Materials: Everything You Need

⚡ Power Supply Requirements: Getting the Right Juice

For lovers of amplifiers with IC, it is best to have a simple power supply, because many have simple variable test bench sources that make testing much easier, in addition to an audio amplifier power for the car, we will necessarily have the simple power supply.

🖨️ Printed Circuit Board (PCB): Design and Files

We provide the files with the PCB, the schematic, the PDF, GERBER and JPG, PNG and provide a direct link for free download and a direct link, "MEGA".

🔧 Assembly Tips and Tricks

🎚️ Performance Optimization

To get the most out of your TDA7386 amplifier, consider these optimization tips:

🤔 Frequently Asked Questions

🎉 Related Projects You Might Enjoy

👋 I hope you enjoyed it!!!

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

🙏 Subscribe to our blog!!! Click here - elcircuits.com!!!

My Best Regards!!!