# Need some LED Circuit help for a hobby project...

Discussion in 'The Projects Forum' started by V4Vendetta636, Feb 11, 2011.

1. ### V4Vendetta636 Thread Starter New Member

Feb 11, 2011
6
0
Hello everyone,
I want to make a LED Project and am in need of some help.

The Basic idea I have is to Write a name using LEDS and with the use of a 4 position switch to alter the effects.
The way I figure it, I should be using about 100-150 leds in series for the 1st effect so that each LED will light up one after the other until the whole string is lit up.
The Next effect I wanted was for it to fade in and fade out the whole string.
And the last effect would be a chaser sequence giving the string a flowing effect from left to right.
(Position 4 would be an on/off switch)
I am a novice when it comes to circuitry but a quick learner

From what I know about LEDs, if I put that many in a series I will need about 350-400V (considering the LEDs are white in color)
I also read Bill Marsden's post about LED tech and wanted to ask about figure 11.4, What effect is that chain of 100 LEDs giving as an output?

Any info and help on setting this up would be much appreciated as I am planning on giving this as a gift to a friend

2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Actually it is only 25 LEDs. It could be expanded to 100's I suppose, but that would be a lot more hassle. The formula for the number of 4017s is the 1st 4017 is 9 LEDs, the others will be 8 per 4017. So it would take 13 4017s to do 100 LEDs.

There is another thread you might find interesting. Use this thread to ask questions for your project. The other thread is an effort to make a PCB for the 25 LED sequencer. It is an ongoing project, but it is happening.

25 LED Open Ended Sequencer

V4Vendetta636 likes this.
3. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
Here's a posibility: 100 stage shift register, serial in " C " allows selection of bar graph type display ot sigle LED chaser & with option of comit tail by applying a hi to" A" . For controlling brightness add PWM to " B " normally hi. That's a lot of parts, one of these for every LED.

File size:
110 KB
Views:
69
4. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
I'm still trying to figure out how a sequencer can make letters myself.

5. ### V4Vendetta636 Thread Starter New Member

Feb 11, 2011
6
0
I was talking with a friend today and he gave me an idea on how to make the string I was looking for.

Output from a NE555 feeding into the base of a 2N2222A and then have an RC series between each LED paralleled off the source. So basically it will come down to 149 resistors, 149 Capacitors, and 150 LED's to make the string. Will upload an initial schematic tomorrow at first chance to give a better idea of what I am saying

If anyone understood that, how does it sound? Is it viable or would there be an easier way?

6. ### thatoneguy AAC Fanatic!

Feb 19, 2009
6,357
718
How are you at programming?

Take a look at the PICAxe or Arduino microcontroller platforms.

Cheaper/faster options would be the "raw" PIC or AVR uC IC running a darlington transistor driver array.

Search Youtube for "Arduino LED effects" to get an idea of what is possible. The parts count is still high, but will allow a much wider range of effects with the same base circuitry. The LED array and resistors are a one time build (hardest "finicky bit" part) you can switch out the controlling logic from discrete logic to uC fairly easily.

7. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
See post #4, if I knew what you were trying to do I could be of more help.

8. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
Not easier, but more likley to work & with some of desired features requested. Could the string be broken up into 2 or 4 parts to cut parts required? Might hook up one letter as a start to check effect.

9. ### V4Vendetta636 Thread Starter New Member

Feb 11, 2011
6
0
Its a very simple concept:
I want to make a string of LED's (100-150)
I want them to have three different effects:
a)Light up in order until the whole string is lit up
b)Have the whole string fade in and fade out (think of a slow pulse)
c)Every odd number led light up and then every even number led light up making the optical illusion of motion.

Thats the basic concept of what I want to do. Think of it as a complex string of christmas lights.

In my initial post I didnt clarify what I wanted as I should have. When I stated I wanted to "write a name" I meant that I would position to leds in such a way that when they lit up, the name would be obvious. I didnt mean to try and make a 3d pseudo holographic display. (The info though was very very interesting but a bit to advanced for my capabilities at the moment) The Positioning of the LED's are irrelevant. I hope what I stated above is a bit more clear on what I am trying to do

10. ### thatoneguy AAC Fanatic!

Feb 19, 2009
6,357
718
Not very simple, actually, especially with the number of LEDs.

A) A "latching counter" or serial-parallel shift register with 100-150 outputs
B) 0%,10%,20%,30%.. -100% duty cycle PWM fade in over 2 seconds, then back to 0%
C) Counter with 4 outputs (4 or 5 is enough to get a good moving effect), with each output driving 25 or more LEDs.

None of A, B, or C use the same electronics, unless you use a microcontroller and shift registers or multiplexers for more I/O, in addition to transistors for more current.

Doing A, or B, or C could be done with a logic IC/Discrete component circuit, but there isn't really a semi-simple way to tie them together to be switchable unless the "brains" are a uC. Not to mention the solder connections will be in the thousands for 150 LEDs.

11. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
I think you need more than alternate LED switching to have moying effect- maybe every 3 to 4 LEDs. Can be done with parallel load parallel out shift reristers, but might take twice as many SRs, common ones are only 4 bit long. Still might consider a 16 LED string to test concept using proto-board.

12. ### V4Vendetta636 Thread Starter New Member

Feb 11, 2011
6
0
Its always simple in theory

13. ### John P AAC Fanatic!

Oct 14, 2008
1,638
225
You probably don't want to hear this, but I think the best way to do it is with a microcontroller (could be Arduino) and as many MAX7219 LED drivers as you need. Each of them can run 64 LEDs, so you'd want 2 or 3 of them. You can turn the LEDs on in any order you want, and you can set various levels of brightness for all LEDs at once. No other components would be needed. All this fooling around with resistors and capacitors strikes me as lots of work for a dubious outcome.

14. ### V4Vendetta636 Thread Starter New Member

Feb 11, 2011
6
0

Alas, I do not have experience with micro-controllers and thus am limited to what little I know about simple tech when it comes to IC's. Is there anything like a "How to for Dummies" that deals with micro-controllers which I can look up in order to get my little project under way?

15. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
The 1st effect (on one at a time until all lit) is the one that makes the project difficult/complex. It means that you need individual control over all of the LEDs, and that means lots of hardware.

If you dropped the 1st effect requirement, the project will be pretty easy to do with relatively few parts.

16. ### V4Vendetta636 Thread Starter New Member

Feb 11, 2011
6
0

I guess dropping the first effect would not be the end of the world
What would I need to get started on creating the circuit for the other two?
Would I still be able to use 100-150 leds?

17. ### John P AAC Fanatic!

Oct 14, 2008
1,638
225
Didn't think you'd go for the processor.

This isn't a complete design, but I think you might be able to build something with mostly 74HC595 shift registers. Each one would only drive 8 LEDs (series resistor also required) so you'll need to order a crate of them!

The 74HC595 has an output-enable line, so you can blank or flash the entire display, or drive the enable with a PWM signal to vary the brightness.

To get the array to light up one LED at a time, you'd start with a blank array, then feed in 1's at a slow rate. If you want to feed them in until the array is entirely lit, hold for a few seconds and then blank it, it's easy to achieve with a counter system.

To get the chase-lights effect, you'd feed in 1's or 0's according to the state of one the bits of your counter. If you chose, say, bit 4, you'd feed in 16 1's, then 16 0's, then 16 1's again and so forth.

The '595 has a double-buffer arrangement, where one clock line moves the data through the actual shift register, but another clock moves the data from the shift to the output pins. To get data to shift through the array and be visible, you'd need to operate first one clock, then the other. This is very easy, potentially just a single inverter, but maybe there's a reason to keep control of both lines. There's also a "Clear" input to each chip, which would be a way to blank the display without shifting in a whole sequence of bits--maybe it's the best way to clear the array for that lighting-in-sequence trick.

Yes, I think this would work. But are you willing to do all that wiring?