Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Cylon eye many leds Design, build help

Status
Not open for further replies.
R

russellito

Newbie level 5
Joined
Oct 26, 2010
Messages
8
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,343
I want to make a circuit that controls about 60 Leds. The number is flexible, but my target is 60. I only need one on at a time, because the "On" Led will move from left to right, then back. I know I can use 555+4017s to count up, and I've designed this schematicView attachment Eye4017.pdf based on cascading 4017s. This schematic doesn't go up to 60 outputs, but adding more 4017s doesn't seem that difficult. I'm going to put this on my breadboard soon to make sure it works, but are there flaws already?

Is there a better way? I mean, if I make this circuit by hand, a way with fewer ICs, solder points?

Also, I'm looking for places to buy the ICs that I will need, the 4017s and 7408 AND chips are $1 a piece at my local store. Jameco.com has SMD versions for <10 cents.

Finally, I used Eagle software to design this schematic, and I was hoping it would help the transition to a PCB by organizing automatically. Does the free version do that? is there other free software that does?
 

I might have used a counter that included a ripple carry out such as 40162 to avoid the external gate. Some counters will go up and down which may be a useful feature for what you're doing.
 

I found the 74F169 which has 4 outputs, up/down counting and the ripple carry out you suggested. its also cheap, I couldn't find the chip you suggested.
So I wouldn't need the gates, I'd only need 15 of these and a 555 to run 60 leds? thats not bad, my next question will be about wiring these, after I do some research.
 

That 74169 is a 4 bit (0-15) counter. You have to decode from binary or BCD to decimal for the outputs. You could use that or 4516, you'll only need 4 of them with 4514 or 4515 decoders.:) I'm not sure the carry out will work in both directions though. I haven't worked with this stuff in a while.
 
Last edited:

Are you really attached to the idea of doing this all via logic and counters? It's neat in a retro sense, but there are more efficient ways of doing this.

Using a $.50 microcontroller and a MAX7219 (controls 64 LED's) would lower your parts count dramatically while simplifying your PCB.

82_1288221476.png
 

Wow that looks fantastic! and only one Led is on at a time? Don't you need a programmer for microcontrollers? I'm pretty new to all this, and google hasn't been very helpful.
 

Beware of the multiplex dimming effect of the 7219. It is described in the data sheet **broken link removed**. To avoid it, you would have to use external drivers which puts you back where you started on parts count.
 

So I just need a MicroController and this chip? that sounds really easy. Where would I get what I need?
 

why not a bunch of shift registers ? (you will need a way to guarantee that only one bit is lit in the full stream...
 

There's a circuit schematic on line that does something similar with far fewer LEDs. It uses a manual pushbutton to feed the first bit and a SR flipflop to repeatedly change the direction of the shift. **broken link removed** In my experiments with various sequencers and LEDs, I often found it useful to build some persistence into the LEDs by adding a few hundred microFarads of capacitance in parallel with each. That way, the lit LED leaves a trail of fading LEDs behind it as it "moves".
 

KJ6EAD said:
There's a circuit schematic on line that does something similar with far fewer LEDs. It uses a manual pushbutton to feed the first bit and a SR flipflop to repeatedly change the direction of the shift. **broken link removed** In my experiments with various sequencers and LEDs, I often found it useful to build some persistence into the LEDs by adding a few hundred microFarads of capacitance in parallel with each. That way, the lit LED leaves a trail of fading LEDs behind it as it "moves".
Click to expand...

Thats a good Idea, I was wondering if I'd be able to incorporate that effect. I am also wondering if any of these designs would support a way to change the speed of the scroll?
To summarize though, I can:
1. Use decade counters that count both ways
2. Use a bunch of shift registers(I don't know what those are...)
3. Use a micro controller and Max7219
Is that an accurate summary of the suggestions?
I'm liking the idea of using the max 7219, seems a lot simpler. I've got one on the way, so maybe I'll figure out how to use it soon...
 


No because with shift registers you dont need the decoders, just stick a led to each parallel output and provide as many shift registers as you need outputs.

Its simpler.
 

Right, So if i'm using 64 leds, I need 8 shift registers. Right?
 

Yes, if you have 64 leds, you need 8 shift registers of 8 bits, serial in, parallel out.

stuff bits in fast enough and no-one will be able to detect the bits shifting. then stop when the bits are in the correct place.
 

Your summary is correct and if it were my project, I'd be opting for the shift register method. That's the way moving message displays are driven and you don't have that multiplex dimming problem.
 

To make the illusion of bits moving backwards, move then 63 steps (do it very fast), then stop for some milliseconds, this will make it appear that they are moving backwards instead of the normal way.
 

Ok, well I think i'm going to pass on the shift registers. It seems like it'll be easier to use the 7219 with a microcontroller. I just info on how to use the controller, program it etc. Any help?
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top