Floating LED light (LED chaser)

yogi009 09 Jan 2024 00:48 23 5205 Cool? (+25)

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TL;DR

A floating LED light / LED chaser project recreates the gradual moving glow used in Christmas decorations and floating turn signals.
The circuit uses a 74HC595-driven, single-sided SMD PCB with eight cathode outputs and a common-anode supply.
It runs from a single Li-Ion 18650 cell, and the potentiometer changes the effect speed.
The LEDs form a three-dimensional ring, and no series resistors are needed when powered from one Li-Ion cell.

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Today`s mini-project is perfect as training material for young electronics students.

Before Christmas, I was asked to make a simple Christmas tree decoration. Among many possibilities, I chose the floating light effect. It can be observed in "ignicle lights" on Christmas trees at Christmas fairs, in new luxury cars (floating indicators), or in the form of light floating in a circle (an interesting application is e.g. a bicycle rear light). It should be noted that this is not a shining running point, but a gradually lit line of light, which in the second phase gradually goes out, giving the effect of a wider moving light.

In this mini-project, I present a scheme proven in practice (there are usually various "interesting" errors on the Internet - I have been trying to combat this thoughtless practice for years), a single-sided PCB (in SMD technology) and the arrangement of elements. In my case, I power the system with a single Li-Ion 18650 cell with an attached charge/discharge control module (of course, the diagram does not take this into account, I use a known module with a nominal value of PLN 1-2).

As you can see, there are no LEDs on the PCB, I made this glowing ring (in my case) in a three-dimensional form, using an idea from YT (just enter the phrase "74HC595 LED chaser"). On the PCB we have 8 outputs for cathodes and plus power supply for a common anode (in my case it is in the form of a circle made of thicker copper wire). When powered by one Li-Ion cell, LED resistors are unnecessary. It is worth adding that we can divide such a circle into 2 or 4 parts and solder 8 LEDs in each section. The potentiometer (peer) is used to change the speed of the effect.

By the way, here`s a tip to help you make a nice circle with LEDs. First, we draw a circle, divide it into 8, 16 or 32 parts and mark the points for drilling 5mm holes. Then we stick our sketch on a piece of board, drill for a few minutes and we have a perfect template. Such help allows you to make many copies of the system in a repeatable way.

Here you can see the first, prototype version of THT (I still had to make a few minor corrections here, as can be seen in the title photo). This is basically the finished "floating turn signal":

A short video showing the achieved lighting effect:

I recommend it to everyone learning the difficult art of soldering, such a system does not require complicated startup and should bring satisfaction :-)

About Author

yogi009 wrote 14693 posts with rating 2650 , helped 848 times. Been with us since 2006 year.

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trojan 12 09 Jan 2024 01:00

Gadgets for points LED Christmas tree 5V kit for assembly [045] Ready. [Read more]

yogi009 09 Jan 2024 01:01

Wouldn t know that this kit was in gadgets. Although here we have greater creative possibilities. I ll understand :-) [Read more]

trojan 12 09 Jan 2024 01:07

And yes, you can. Start by digging out copper in the mine, silicon in the deposit... A smoke machine would probably come in handy as well. [Read more]

Matheu 09 Jan 2024 03:09

1) @trojan12 : post #2 thanks for the tip/info about Gazeta! 2) post #4 Why do you mock/discourage independence? walking this way- ` What for to learn addition/multiply/integration?!? ... [Read more]

rafi8112 09 Jan 2024 08:36

And I personally appreciate such work. Satisfaction with the built devices, even the simplest ones, is priceless, in the full sense of the word. If someone wants to be a real electronics designer, he or... [Read more]

efi222 09 Jan 2024 11:31

I support my friend yogi009 and rafi8112 here Some of us certainly remember the times when we had even "color" TV sets (Neptune). There was enthusiasm and pressure for various structures. Fighting and... [Read more]

yogi009 09 Jan 2024 15:40

I added some pictures and a short video to the title post. [Read more]

Anonymous 09 Jan 2024 17:04

I know that it t you protect the PCB with a soldermask after milling? [Read more]

saly 09 Jan 2024 23:25

It`s nice to build something sometimes and think about how to do it without a microcontroller, we should have an order to build every third project without a microcontroller. All the knowledge from years... [Read more]

yogi009 10 Jan 2024 00:08

Because this is the first training prototype (made in THT), I ultimately made the second version in SMD and this one was treated with varnish for electronic boards. I don t intend to buy it wholesale and... [Read more]

żarówka rtęciowa 10 Jan 2024 13:16

Hello You can do without 555, just use a generator on bipolar transistors. In the retro version, you can use a counter, e.g.: 7490, and a BCD decoder, e.g.: 74145. This is how bells - music boxes... [Read more]

yogi009 10 Jan 2024 13:53

Of course. It`s a matter of choice. [Read more]

ken-wawa 11 Jan 2024 17:15

Cool project! What program did you use to design the printed circuit board? Once upon a time, as a young boy, it was a lot :P I soldered things like that. But some time ago, as a reminder of the old times,... [Read more]

yogi009 11 Jan 2024 21:42

KiCad :-) [Read more]

ken-wawa 11 Jan 2024 21:55

I used to draw some simple circuits in KiCad, but I didn`t design the board itself. How do you rate the friendliness of the user interface and reducing the risk of errors? Is there any control? [Read more]

yogi009 11 Jan 2024 21:58

I switched to KiCad when Eagle was bought by Altium and the subscription was introduced. KiCad has a slightly different way of flowing information, there are simply further steps that need to be followed.... [Read more]

ken-wawa 12 Jan 2024 02:20

I have to check it out when I have some free time... :) [Read more]

damian1115 22 Jan 2024 19:14

You did it quite nicely, I like it, I have it +. The system is simple and worth recommending to younger "electrode" students. Putting together a KIT is not the same as building something yourself, especially... [Read more]

yogi009 22 Jan 2024 19:26

The video is included in the title post. A decoupling capacitor is always useful, although here it is not a major issue. However, NE555 applications provide for such an element. [Read more]

FAQ

TL;DR: This 8-output LED chaser drives up to 32 LEDs, and the author says, "quite intelligent devices were built" before microcontrollers. It shows beginners how to create a floating LED ring with NE555 timing, a 74HC595 shift register, a speed potentiometer, and a single 18650 Li-Ion cell, without complex startup work. [#20900987]

Why it matters: This project gives beginners a practical way to learn timing, shifting, PCB making, and LED wiring from scratch instead of only assembling a ready-made kit.

Approach	Main parts	Power noted in thread	Best use	Trade-off
74HC595 + NE555	74HC595, NE555, potentiometer	1× Li-Ion 18650	Training project with 8, 16, or 32 LEDs	Requires custom wiring and PCB work
555 + 4017	Classic discrete LED chaser logic	Not specified	Familiar beginner alternative	Less exposure to 74HC595 operation
Microcontroller-based chaser	MCU not specified	Not specified	Flexible effects	Teaches less pure logic basics
Ready-made 5 V kit	Pre-made Christmas tree kit	5 V	Fast assembly	Less design freedom

Key insight: The core lesson is not the decoration itself. It is that an 8-output 74HC595 can generate a wider, "floating" light band and also teach real DIY electronics skills, from PCB transfer to non-microcontroller logic.

Quick Facts

The board exposes 8 cathode outputs plus a common-anode positive supply, and the ring can be built as 8-, 16-, or 32-LED sections. [#20927233]
The author powered the circuit from one Li-Ion 18650 cell and used a separate charge/discharge protection module costing about PLN 1-2. [#20899190]
The circular lamp template uses 5 mm holes drilled at evenly spaced points after dividing a drawn circle into 8, 16, or 32 sections. [#20899190]
The final PCB tool was KiCad, while the first training prototype was made in THT and the later version in SMD. [#20904321]
One practical improvement discussed was a 10 nF decoupling capacitor from NE555 pin 5 to ground to reduce possible disturbances. [#20923341]

How do you build a floating LED light effect with a 74HC595 and NE555 instead of using a microcontroller?

You build it with an NE555 clock, a 74HC595 for 8 sequential outputs, a potentiometer for speed, and an LED ring wired to those outputs. The board provides 8 cathodes and one common-anode positive rail, so the light grows and fades as grouped LEDs switch in sequence. The author chose this specifically to teach non-microcontroller logic and said such a circuit should not require complicated startup. [#20899190]

What is a floating LED effect, and how is it different from a simple running LED point?

A floating LED effect is a wider moving band of light, not a single bright dot. "Floating LED effect" is a lighting pattern that gradually lights a line of LEDs and then gradually extinguishes it, creating a broader moving glow rather than one sharply defined running point. The thread compares it to icicle lights, luxury-car indicators, and circular bicycle rear lights. [#20899190]

Why are current-limiting resistors unnecessary in this LED chaser when it is powered from a single Li-Ion 18650 cell?

In this design, the author states that LED resistors are unnecessary when the circuit runs from one Li-Ion 18650 cell. That claim is specific to this build, which uses a single cell and a common-anode ring connected to the 74HC595 outputs. If you change the supply arrangement, that assumption may no longer hold, so this answer applies only to the exact one-cell setup described. [#20899190]

How can you wire 8, 16, or 32 LEDs to the 8 outputs of a 74HC595 to create a circular 'droplet' light effect?

You map repeated LED positions onto the same 8 outputs. For 32 LEDs, use 4 sections of 8 and connect LEDs 1, 9, 17, and 25 in parallel to output 1, then 2, 10, 18, and 26 to output 2, and so on. For 16 LEDs, the thread gives a mirrored option: LEDs 1 and 16 go to output 1, LEDs 2 and 15 to output 2, etc. [#20927233]

What is a decoupling capacitor on the NE555 control pin, and why did one user recommend adding 10 nF between pin 5 and ground?

A decoupling capacitor on NE555 pin 5 helps reduce disturbances in the timing circuit. "Decoupling capacitor" is a passive component that shunts unwanted noise away from a sensitive node, improving stability; here it was suggested on the NE555 control pin, where small voltage disturbances can affect timing behavior. One user recommended 10 nF from pin 5 to ground, and the author agreed that NE555 applications provide for such an element. [#20923380]

How do you make a precise circular LED template with evenly spaced 5 mm holes for a ring-shaped lamp?

You make it with a paper layout and a drilled board template. 1. Draw a circle and divide it into 8, 16, or 32 equal parts. 2. Mark the LED positions and drill 5 mm holes through a board. 3. Use that drilled board as a repeatable jig for many identical LED rings. The author recommends this method because it quickly produces a clean, accurate circle. [#20899190]

Why would someone choose a 74HC595-based LED chaser over the classic 555 plus 4017 approach for a training project?

You choose it to teach a different logic block than the usual 555-plus-4017 beginner circuit. The author explicitly says many young electronics learners have not yet encountered the 74HC595, so this project gives them a concrete way to analyze how that logic device works. As the project author put it, “we need to show that before the era of processors, quite intelligent devices were built.” [#20900987]

What is solder mask, and when is board varnish enough protection for a homemade PCB prototype?

Solder mask is the durable insulating coating normally applied over copper traces, but board varnish can be enough for a short-run prototype. "Solder mask" is a protective PCB coating that insulates exposed copper, reduces accidental solder bridges, and improves durability; homemade prototypes may instead use board varnish when production-grade finish is unnecessary. The author skipped solder mask on the first THT training prototype and used varnish on the later SMD version for just 2-3 Christmas trees. [#20900987]

Which PCB design program was used for this project, and how beginner-friendly is KiCad for small DIY electronics boards?

The PCB was designed in KiCad, and the author rates it as quite decent for small projects once you learn its workflow. The key point is that KiCad has a different information flow, with further steps that must be followed in order. For simple single-sided DIY boards, the thread presents it as usable and practical rather than difficult. [#20904361]

How does KiCad compare with Eagle for designing simple single-sided PCBs after Eagle moved to a subscription model?

In this thread, KiCad replaced Eagle because Eagle moved to a subscription after being bought by Altium. The author switched platforms for that reason and says KiCad works well for small boards once you adapt your habits to its different flow. For simple DIY layouts, the comparison favors KiCad on accessibility and continuity of use. [#20904361]

What are the current limits of the 74HC595 when driving parallel LED sections, and how do they affect 8-, 16-, and 32-LED layouts?

The thread does not give a numeric current limit for the 74HC595, but it clearly says that output current is the factor that constrains LED grouping. Practically, 8 LEDs use one section, 16 LEDs can use paired positions, and 32 LEDs use 4 parallel sections tied to the same 8 outputs. The edge case is simple: if the grouped LEDs demand more current than the chip can supply, your chosen layout is no longer valid. [#20927233]

How should you adjust the potentiometer in a 74HC595 LED chaser to control the speed of the flowing light effect?

Adjust the potentiometer until the moving band looks smooth at the speed you want. The thread states that the potentiometer directly changes the effect speed, so it acts as the user control for the NE555-driven timing rate. In practice, turn it one way for a slower drift and the other for a faster sweep, then stop when the 8-step sequence looks visually continuous. [#20899190]

What are the advantages of building this LED chaser from scratch instead of assembling a ready-made 5 V Christmas tree LED kit?

Building it from scratch teaches design, PCB transfer, soldering, and wiring decisions that a 5 V kit does not. Several participants stress the satisfaction of making a complete device yourself, from etching the board to assembling SMD parts, rather than only putting together a ready-made product. The thread also notes greater creative freedom, including custom ring shapes and 8-, 16-, or 32-LED arrangements. [#20899202]

What alternative retro logic circuits could replace the NE555 and 74HC595, such as a transistor oscillator with 7490 and 74145?

A retro alternative is a bipolar-transistor oscillator feeding a 7490 counter and a 74145 BCD decoder. One participant says you can omit the 555 entirely and build the generator from bipolar transistors, then use 7490 and 74145 parts, similar to bell and music-box circuits from about 30 years ago. That makes the project even more logic-focused and less dependent on newer integrated approaches. [#20901631]

How do you troubleshoot a homemade iron-transfer PCB for an LED chaser if the effect is unstable or the board quality is only average?

Start by checking the basics the thread actually flags: timing stability, board protection, and PCB quality. 1. Add the recommended 10 nF capacitor from NE555 pin 5 to ground. 2. Inspect the iron-transfer traces and soldering, especially on the first THT prototype. 3. If the board will stay in service, protect it with electronic board varnish. The author openly says the iron-transfer result was “more than enough” rather than perfect, so average cosmetic quality does not automatically mean failure. [#20900987]

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