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Wanted to generate a LED fading effect (fade-in and fade-out) for my upcoming video tutorial using the 555 timer IC. I already have a video where I used LM358 Dual Operational Amplifier IC and another one with Arduino to generate the LED fading effect. YouTube, is full of video showing how to generate the fading effect using 555 timer IC. However, none of them produce a true fading effect. Some just fades-in but never fades-out. And there is literally no explanation of how they are generating the fading effect other than just showing how to assemble the components. In this tutorial, I am going to show you guys how to create a true LED fading effect using the 555 timer IC. I will also explain how the circuit works and how changing components change the fading effect of the LEDs. Components Required For this tutorial you need: 1 x 555 Timer IC 1 x 47KΩ Resistor 1 x 220Ω Resistor 1 x BC548 NPN Transistor 1 x 33µF Capacitor, and 1 x Few Blue LEDs Circuit Diagram The heart of this circuit is the 555 timer IC. Pin No.1 of the IC is connected to GND. By connecting Pin 2 and 6 of the 555 timer IC, we put the IC in astable mode. In astable mode, the 555 timer IC acts as an oscillator (re-triggering itself) generating square waves [PWM Signals] from the output Pin no. 3. 3 other components connect to this junction. 1st one is the 33µF capacitor. The positive pin of the capacitor connects to the junction and the negative pin is connected to the GND. 2nd one is the 47KΩ resistor. One of its legs connects to the junction and the other leg connects to the Output pin, Pin No.3 of the IC. 3rd one is the Base of the BC548 NPN transistor. The collector of the transistor along with Pin 8 and 4 of the IC connects to the +ve terminal. of the battery. The LED along with its current limiting resistor is connected to the Emitter of the transistor. That's it as simple as that. Alright, now I am going to demonstrate how this circuit works with the help of an animation. How The Circuit Works When Pin 2 of the IC detects voltage LESS than 1/3rd of the supply voltage, it turns ON the output on Pin 3. And, when Pin 6 detects voltage MORE than 2/3rds of the supply voltage, it turns OFF the output. This is how the trigger pin (Pin2) and the threshold pin (Pin6) of the 555 timer IC sense voltages and controls the output at Pin 3. The Capacitor attached to the circuit will be in a discharged state immediately after firing up the circuit. So, the voltage at Pin 2 will be 0v which is less than 1/3rds of the supply voltage, this will turn ON the output on Pin 3. Since Pin 3 is looped back to Pin 2, it will start charging the Capacitor via the 47KΩ resistor. At the same time the base current of the transistor also increases causing the LED to slowly "fade-in". Once the voltage across the capacitor crosses 2/3rds of the supply voltage, Pin 6 turns OFF the output. This causes the capacitor to slowly discharge causing the base current to fall and hence the LED starts "fading-out". Once the voltage across the capacitor falls below 1/3rd of the supply voltage, Pin 2 turns ON the output, and the above cycle continues. You can hook up a multimeter to the circuit to measure the charging and discharging of the capacitor. Breadboard Demo So, here is a quick demo on a breadboard. In the current setup I have a 33µF Capacitor and a Blue LED on the breadboard. Replacing the 33µF Capacitor with a 100µF Capacitor makes the LED fade in-and-out slower as the 100µF capacitor charges and discharges slower than 33µF Capacitor. Also by replacing the "Blue LED" with a "Red LED", we can make the LED to stay "on" longer than the blue one with the same value of capacitor. This is because the "Forward Voltage" (Vf) of the Blue LED is higher than that of the Red LED. "Forward voltage" is the minimum amount of voltage that is required to allow an electrical component to turn on. The red, green and yellow LEDs have relatively "low" forward voltage ranging from 1.6-2.2V and hence stays on longer when the capacitor slowly charges or discharged. However, blue and white LEDs starts conducting from 2.5-4V and hence, when the discharging capacitor's voltage hits the threshold the LED turns off faster than the other colors. I have provided a link to how the forward voltage works in the description below. If you connect few LEDs in series, the forward voltage adds up and hence it will require more voltage to turn on the LEDs. You need to add a current limiting resistor between the emitter of the transistor and the LED to avoid an internal short-circuiting inside the led. The Board To make it easy for you guys, I have created this tiny little "555 LED Fader Module". After assembling the components, you just need to power this module by providing a voltage between 5v to 15v to fade the LED. So, this is how my board looks like in 2D and 3D. There are 16 breakout boards in this 100cm x 100cm assembly. You can download the gerber file from the link provided in the description below and order it from PCBWay. Soldering Let me quickly show you guys how to assemble the components to this custom made board. Let's start by soldering the IC Base to the board. Then let's solder the two resistors to the board. Next, lets solder the capacitor followed by the transistor to the board. Then, lets solder a blue LED to the board. Once done, let's insert the 555 timer IC to the IC base. To conclude the setup, I soldered 2 x Female pin headers to the board. You can either solder a pair of female pin-header or male pin-header or solder a pair of wires directly to the board to power this module. Demo Cool, so this is how my module finally looks like. You can install female pin-headers in-place of the LED or Capacitor if you plan to use this as a development/testing board instead of a module. Thanks Thanks again for checking my post. I hope it helps you. If you want to support me subscribe to my YouTube Channel: https://www.youtube.com/user/tarantula3 Video: Visit Full Blog Post: Visit LED Fader - With or Without Arduino: Visit Adjustable Single/Dual LED Flasher Using 555 Timer IC: Visit Other Links: Gerber: Download Github: Visit Simulation: Visit What Is Forward Voltage: Visit Support My Work: BTC: 1Hrr83W2zu2hmDcmYqZMhgPQ71oLj5b7v5 LTC: LPh69qxUqaHKYuFPJVJsNQjpBHWK7hZ9TZ DOGE: DEU2Wz3TK95119HMNZv2kpU7PkWbGNs9K3 ETH: 0xD64fb51C74E0206cB6702aB922C765c68B97dCD4 BAT: 0x9D9E77cA360b53cD89cc01dC37A5314C0113FFc3 LBC: bZ8ANEJFsd2MNFfpoxBhtFNPboh7PmD7M2 COS: bnb136ns6lfw4zs5hg4n85vdthaad7hq5m4gtkgf23 Memo: 572187879 BNB: 0xD64fb51C74E0206cB6702aB922C765c68B97dCD4 MATIC: 0xD64fb51C74E0206cB6702aB922C765c68B97dCD4 Thanks, ca again in my next tutorial.
Have an awesome project in mind using some LEDs. In that project I will be using some LED Fading Effect and few LED Chaser Circuits. But before jumping onto that, I thought I should create a short tutorial and show you guys how to fade a LED with or without an Arduino automatically or manually using a potentiometer. Video: https://youtu.be/IIUsdICycOw Sponsors This video is sponsored by PCBWay. PCBway: only $5 for 10 pcbs from https://www.pcbway.com/?from=CZcouple PCBWay specialize in manufacturing of very high quality, low-volume, colored PCBs at a very budgetary price. In addition to the standard PCBs, you can also order Advanced PCBs, Aluminum PCBs, FPC/Rigid-flex PCBs. They also provide PCB assembly and other related service which can meet your needs to the greatest extent. The ordering process from PCBWay is very easy. Once I had my design ready, I just had to upload the gerber file to the PCBWay's website and select the type, color and any other customization that I want and then just send it for fabrication. For my project, I choose the black color. PCBWay ships from china to most of the countries of the world within 3 to 7 business days. Talking about the quality, its absolutely mind-blowing. Without Arduino Lets first create the fader circuit without an Arduino. The base of this circuit is an operational amplifier IC named LM358. In this circuit, initially, the LED slowly glows with increasing brightness & after reaching its maximum brightness, the LED slowly dims its brightness and the process continues. Automatic Fading Components Required For the Non-Arduino bit we need: 1 x LM358 IC 1 x BC547 Transistor 1 x 0.47µF Capacitor 2 x 4.7KΩ Resistors 1 x 22KΩ Resistor 1 x 10KΩ Resistor 1 x 4.7MΩ Resistor 1 x 220Ω Resistor 1 x LED and a 9V Battery How This Circuit Works To get the fading effect we need to generate a series of triangular waves. Because of the triangular waves, the LED starts glowing slowly and then slowly dims off and the cycle continues. This setup is done using the LM358 IC. LM358 is a dual operational amplifier (Op-Amp) IC, integrated with two op-amps powered by a common power supply. Pins 1, 2, and 3 are one op-amp channel, and pins 5, 6, and 7 are the 2nd op-amp channel. As the capacitor charges and discharges the state of the PIN 3 switches from high to low and based on that the PIN 2 of the op-amp obtains the desire output. If you want to know more about this IC, please check out my "Tutorial No 21 : DIY - IR Module" : https://youtu.be/_M8FQIPi1qk. So, basically the op-amp here is used for voltage level detection. In this circuit, we are applying a voltage on positive pin (PIN-3) and the voltage to be detected is applied at negative pin (PIN-2). The transistor acts as a signal amplifier. You will need this if you are attaching a cluster of LEDs however for just 1 LED you can simply remove it. The Board So, this is how my board looks like in 2D and 3D. There are 15 breakout-boards in this 100cm x 100cm assembly. Component Assembly Now, lets solder all the components to the board. Lets first solder all the resistances to the board. Then lets solder the transistor followed by the capacitor to the board. After that lets solder the LED and the female pin header. To conclude the setup, lets solder the IC base and then install the IC into it. Demo So, this is how it looks like. Good thing about LEDs is that they can be easily controlled as compared to the traditional light bulbs. Which means you can easily change their intensity based on your need. Just by making a slight modification to this circuit you can change the brightness of a LED Lamp when someone walks in or out of a room. Manual Fading Using PWM Now, if you want to get the same dimming effect but want to manually control the intensity, you will have to find a way to modulate the pulse sent to the LED or group of LEDs using a potentiometer. I am going to do this by generating PWM Signals. What is PWM? Pulse Width Modulation, or PWM, is a technique for getting analog results with digital means. PWM value varies from 0 to 255. The bigger the value of PWM, the brighter the LED is and vice versa. - If PWM = 0, it is same as GND, so the LED will be OFF - If PWM = 255, it is same as VCC, so the LED will be fully ON To get varying analog values, you change, or modulate, that pulse-width. If you repeat this on-off pattern fast enough with an LED, the result is as if the signal is a steady voltage between 0 and 5v controlling the brightness of the LED. In this setup, we are going to use the 555 Timer IC in Astable mode (A free-running multivibrator that has NO stable states but switches continuously between two states this action produces a train of square wave pulses at a fixed known frequency) to generate the PWM Signals. 555 Timer IC will vary the voltage delivered to the LEDs to achieve the Dimming effect of the LED. Components Required For this setup we need: 1 x 555 Timer IC 1 x LED 1 x 220Ω Resistor 2 x 1N4007 Diodes 1 x 50KΩ Potentiometer 1 x 10nF Capacitor 1 x 100nF Capacitor and a 5V Battery How This Circuit Works Based on the charging and discharging timings of the Capacitor, a PWM Signal is generated at PIN 3 (OUT PIN) of the 555 Timer IC. The output is then sent to the LED to produce the dimming effect. Demo So, this is how it looks like. By rotating the knob of the 10K Pot we can adjust the brightness of the connected LED. With Arduino Now, lets repeat these setups using an Arduino. The beauty of Arduino is that it has 6 digital pins that can be used as PWM outputs (3, 5, 6, 9, 10, and 11). PWM signals are sent using the analogWrite() function by passing a value between 0 - 255. - analogWrite(255) requests a 100% duty cycle (always on), - and analogWrite(127) is a 50% duty cycle (on half the time), and so on. Components Required For this setup we need: Arduino UNO/Nano whatever is handy 1 x Breadboard 1 x LED 1 x 220Ω Resistor 1 x 10KΩ Potentiometer Automatic Fading Connect the positive leg of your LED to the digital output PIN9 of your Arduino through a 220Ω resistor. Connect the negative leg directly to the GND. That it, that's how simple it is. The Code After declaring PIN 9 as LedPin, and setting up the pinMode in the setup() section, we are going to loop through and dim the LED in the loop section. By gradually increasing the PWM value from 0 to 255, and then back to 0 we can get the fading effect. In this sketch, the PWM value is set using a variable called 'brightness'. Each time in the loop, it increases by the value of the variable 'fadeAmount'. If brightness is at either extreme of its value (either 0 or 255), then 'fadeAmount' is changed to its negative. So, if the fadeAmount is 5, then it is set to -5 and if it is -5, then it is set to 5. The next time through the loop, this change causes brightness to change its direction. A delay is added to control the speed of the fading effect. Demo So, this is how it looks like. Manual Fading Connect the positive leg of your LED to the digital output PIN6 of your Arduino through a 220Ω resistor. Connect the negative leg directly to the GND. Connect the left (or right) pin of the 50KΩ PoT to VCC and then connect the right (or left) pin of the PoT to the GND. Now, connect the 'data' pin of your potentiometer to the Analog PIN 'A0' of the Arduino. In this circuit, the potentiometer is working as a voltage divider. One of the outer pins is connected to the GND, the other to Vcc and the middle pin is the voltage output. The wiper position in this setup determines the output voltage. Now, lets have a look at the code. The Code Based on my setup, I set the LedPin as 6 and Potentiometer pin Pot as A0. Another variable 'Knob' is used to read and store the value of the potentiometer. pinMode of the LedPin is set to OUTPUT and we don't need to do anything for the PoT as its default value is already set as input. In the 'loop()' section I am first reading the value of the PoT using the 'analogRead()' function and then mapping its value between 1 to 255. A potentiometer intakes a value between 1 and 1024, but in our setup it has to be between 1 to 255. The 'map()' function divides the value read from the potentiometer into equal intervals of 1/255, which is then sent to the LED using the 'analogWrite()' function. Demo So, this is how it looks like. Thanks Thanks again for checking my post. I hope it helps you. If you want to support me subscribe to my YouTube Channel: https://www.youtube.com/user/tarantula3 Full Blog Post: https://diy-projects4u.blogspot.com/2021/02/led-fader-with-or-without-arduino.html Video: https://youtu.be/IIUsdICycOw Gerber File: 1. Gerber : https://drive.google.com/file/d/1w1hHZBFsXQR74ZTn04097awaAUqMndJi/view?usp=sharing The Code: 1. Automatic Fading : https://drive.google.com/file/d/1hab3sISIlurrPQBat80OLb90RXqQKzLZ/view?usp=sharing 2. Manual Fading Using PoT : https://drive.google.com/file/d/1TzXdVO5lVjPNaw_NPSUexIye3WZGJ6cj/view?usp=sharing Sketches: https://drive.google.com/file/d/1_WtmESof7kSyuJ_cmkkFZ8E8mdQXl3Z9/view?usp=sharing BTC: 1M1PdxVxSTPLoMK91XnvEPksVuAa4J4dDp LTC: MQFkVkWimYngMwp5SMuSbMP4ADStjysstm DOGE: DDe7Fws24zf7acZevoT8uERnmisiHwR5st ETH: 0x939aa4e13ecb4b46663c8017986abc0d204cde60 BAT: 0x939aa4e13ecb4b46663c8017986abc0d204cde60 LBC: bZ8ANEJFsd2MNFfpoxBhtFNPboh7PmD7M2 Thanks, ca again in my next tutorial.