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Pulsing LED Circuit: What It Is and How to Build One

Does your project involve creating light effects, and you’re looking for the best method to make them? If your answer is yes, you should consider the pulsing LED circuit.

The pulsing LED circuit is a simple but powerful way to create light effects for decorative projects or other projects dealing with lights.

However, it may be not easy to assemble correctly on your first try. But that’s not a cause for concern.

In this article, you’ll learn how to build a simple pulsing LED circuit and make it work.

Let’s jump right in!

Fading and Pulsing LED using 555

The pulsing or fading LED circuit is a small and easy project that allows you to control LED pulsates or fades with a 555 timer IC.



Interestingly, you can achieve two types of fade effects with this circuit. These include the fade-out fade-in and the fade-in fade-out effects.

Also, you can use this simple circuit for building decorative lights or simple pulsating LED strips.

LED Strips

LED Strips

So, let’s take a closer look at how this circuit works.

How Does it Work?

The 555 timer IC is the equivalent of a heart in this circuit. So, with the 555 timer IC and a transistor, you can run most circuit operations—coupled with a few resistors and capacitors.

Plus, the timer IC works in a stable multivibrator mode for this circuit. Also, the timer IC creates times pulses that control how the LED fades in and out.

Additionally, the resistors help you determine the amount of delay when the LED fades in and out. But that’s not all. The capacitor also plays a vital role in the fading of the LEDs.



Also, the transistors are responsible for amplifying the signals moving to the LEDs to a level enough to light them up—without damaging them.

Moreover, the operating voltage of this circuit ranges anywhere between 9v to 12v. Plus, if your LED has a current rating of 25mA, it’ll be compatible with this circuit.

Note: You can add more LEDs to your circuits by simply connecting your LEDs with a resistor in parallel.

Circuit Diagram

Here’s the diagram and schematic of the circuit we’ll be learning how to build.

Circuit Diagram

Circuit Diagram

Components Needed

To build this circuit, you’ll need the following components and tools:

How to Build

Now, we’ll take you through the step-by-step method to produce a perfect and working pulse or fade LED circuit.

Step 1: Gather and Inspect Your Components

First, ensure you have all the necessary components and tools. Also, check if your details are working correctly.

Then, check your capacitor voltage to see if you have a bad capacitor or resistor. And ensure to replace any faulty one before you start building to avoid errors.

Step 2: Build Your Circuit Board

Then, the next step is to assemble your circuit board.

Also, for an easier understanding, if you can’t read schematics, we’ve added both the circuit schematic and diagram side by side above so you know where and how to place your components.

Step 3: Solder your Switch and Resistors

Now you can start building your circuit by soldering your switch to the circuit board. We recommend soldering it to the edge of the board. Also, don’t forget to leave a hole in your board for your 9v battery.

Note: when soldering, make sure it looks like a mini volcano. If it doesn’t, then you’ll most likely have a cold joint. Also, make sure you heat the lead first before adding the solder.

Add your resistors to the board once you’ve soldered your switch. Also, bend the resistor leads to avoid falling out from the board.

Now, solder the first 1K resistor by pressing the resistor flush to the board and soldering to make a connection. Next, do the same thing for the other resistors in this order: 33k, 1k, 1k, and 330-ohm resistor.

Note: don’t cut off the excess leads yet. They’re still vital if you want to make connections without wire later.

Step 4: Solder Your Transistor and Capacitors

Next, place your transistor according to the circuit diagram, which should be in front of the three resistors you soldered in the middle.

Also, note that orientation is essential, so make sure the transistor’s flat side faces the resistors. Then, adjust the leads to get the position and proceed to solder.

After this, add your capacitors to the circuits according to the diagram.

Don’t worry if you use too much solder. You can use your solder sucker to remove all excess solder from your circuit.

Step 5: Make Your Connections

First,  solder the 1k resistor closest to the switch to the positive lead of the 100uF capacitor. Next, we recommend bending the tip of the resistor towards the side of the capacitor. Once you’ve made the connection, you can remove the excess leads—if any.

Next, take the transistor’s lead closer to the 100uF capacitor and connect it to the 1k and 33k resistors, creating an L-shaped joint.

Also, take the middle lead of the transistor and connect it to the mid 1k resistor. After running these connections, cut off the excess leads.

Check the 220uF capacitor and connect the positive part to the transistor, and the negative lead to the negative charge of the 100uF capacitor.

For the bottom half, join the 220uF capacitor’s negative lead to the closest 1K resistor lead but don’t cut off the extra charges.

You can add your LED to the circuit when you’re sure of your connections. Afterward, you can connect the lead of the 330-ohm resistor to the LED’s positive terminal and solder the LED’s negative terminal to the remaining 1k resistor leads. Still, take that connection and solder it to the battery’s positive terminal.

Step 6: Finalizing

After concluding the setup, there should be two resistor leads without connections: the 1K and the 33K. Now, you’ll have to create a solder bridge to build a strong bond between the resistors. Afterward, you can cut off the lead of the 1k resistor. First, however, keep the 33k resistor’s information and connect it to the battery’s positive terminal, and as usual, cut off the excess leads.

Note: don’t throw away your excess leads. They come in handy when you want to make a connection without wires. Make sure you don’t connect the information of the outer switch so you can turn your circuit on and off without having to remove the battery.

Final Thoughts

Building a pulsing LED circuit is a fun and easy project because of its basic electronics. Once you’ve set everything up with all connections, all you have to do is test the circuit.

However, you’d have to crosscheck your circuit and connections before testing. By doing so, you’ll protect your battery or components from getting damaged.

If you have a lot of blobs from using too much solder, don’t worry about it. Clean up, and your circuit will be alright.

If you found this project interesting and would like to ask more questions, feel free to reach us, anwe’llll be happy to help.

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Emma Lu
Our professional engineering support saves our customers a lot of trouble and loss. >>>>>> After you place the order, our engineer will conduct technical reviews to make sure the parts can be mounted well/correctly on the boards. We will check if the component packages match well with the Gerber footprints, if the part numbers you provided match well with the descriptions, and if the polarity is clearly marked. >>>>> When your design is ready, please send your Gerber and BOM so we can quote and start!