Go Down

Topic: 555 and shift register (Read 4442 times) previous topic - next topic

togethernessnyc

Hi!

I'm trying to send a signal out from a 555 timer to a shift register.  The shift register has 8 LEDs.  The aim is to have them fading in and out in sequence.  This seems like it would be a fair common and simple circuit, yet I can't find any schematics on line. 

I did find these two videos, but they don't offer much instruction: 

http://www.youtube.com/watch?v=rJo88Vjm96s
http://www.youtube.com/watch?v=82uf0iOHmCs

I've also been trying to track down something for Fritzing. 

Can anyone offer some guidance? 

codlink

The only thing I found was off one of your videos.  It's a pic of his PCB.  http://img839.imageshack.us/img839/1410/8bitshiftregister.jpg

Should be enough info there.
//LiNK

cmiyc


I've also been trying to track down something for Fritzing. 

https://www.google.com/search?q=Fritzing
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

togethernessnyc

@codlink, @James C4S

Thanks!

James, I have Fritzing, I was looking for an actual schematic. 

Codlink, yes I saw that, but part of the reason I was looking for a Fritzing schematic is because I'm new, schematics like the one he posted are sometimes a little difficult for me to translate into the real world.  I'm trying to get better at it, but this one is a little beyond my level right now. 

cmiyc

#4
Mar 31, 2013, 05:07 pm Last Edit: Mar 31, 2013, 05:08 pm by James C4S Reason: 1
That's not a schematic.  That's a PCB layout which gives you very little information.

If the original creator doesn't have a schematic, I'm not sure you're going to be able to reverse engineer the circuit.

But could piece together rhe parts parts your self.

You need a 555 to act as a clock to a shift register.  Maybe some transistors for the LEDs.  You should be able to find the individual peices, start drawing your own schematic, and ask questions in forums like this.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

codlink


That's not a schematic.  That's a PCB layout which gives you very little information.


I noticed.  But it has all the values of the components which can be translated into a schematic.

Quote
If the original creator doesn't have a schematic, I'm not sure you're going to be able to reverse engineer the circuit.


I'm sure I could. 

Together, check back later, and I will see if can't draw up a schematic for ya.
//LiNK

Grumpy_Mike

#6
Mar 31, 2013, 06:38 pm Last Edit: Mar 31, 2013, 06:41 pm by Grumpy_Mike Reason: 1
Quote
The shift register has 8 LEDs.  The aim is to have them fading in and out in sequence.

Switching on and off fine but I don't see how you can fade up and down without a more complex circuit.

Those videos don't show any fadeing behavour.

codlink

http://www.pyroelectro.com/tutorials/pcb_design_diy_2_layer/parts.html
//LiNK

togethernessnyc

First of all, once again, thanks everyone for your input on this.  This is still an ongoing project so every bit of information counts. 

@codlink, great link, thank you!  it doesn't quite illustrate the fade that i'd like to achieve, but, like @James C4S suggested, I think this may have to do with adding some transistors.  i've already constructed a fading LED as per the following link, but there's a big difference between reading about something, constructing it, and fully comprehending how the machinery created the results, especially for newcomers (like myself): 

http://www.555-timer-circuits.com/up-down-fading-led.html

The same website has the following project as well, but uses a decade timer: 

http://www.555-timer-circuits.com/knight-rider.html

I'd still like to stick with the shift register, combined with the fade.  I like the simplicity of these IC's.  Arduino was my introduction to electronics, but I really like the fact that some things that can be so tempting to do with Arduino can be achieved much more simply, cheaply, and offer a more direct, hands-on learning experience of the mechanics of electrical engineering.  Plus, I find analog fades to be much nicer than digital fades. 

Grumpy_Mike

So take the fade circuit, throw away the 555 and feed the 33K from the output of the shift register.

togethernessnyc

#10
Apr 01, 2013, 09:34 pm Last Edit: Apr 01, 2013, 09:44 pm by togethernessnyc Reason: 1
@Grumpy Mike, sounds great . . . does that mean that the 555 actually is not creating the fade, but rather the 33k resistor?  If so, sounds like we've found a solution!   :)

In other words, I was trying to use the 555 as a clock, but if the shift register actually has it's own clock then we may be in business if we can just control the steps with the 33k. 

Grumpy_Mike

The fade is done by the resistor and capacitor charging and discharging. The resistor to the 555 controls if it is charging or discharging. So the output of your shift register will do the switching.

togethernessnyc

@Grumpy Mike, I do believe you've nailed it . . . thanks for your help!  And thanks to everyone else who chimed in :)

Go Up