Go Down

Topic: Possible to operate a shift register manually with switches? (Read 6032 times) previous topic - next topic

Start2222

Thanks for that demo of shift registers!  I was reading about them the other day, and your demo helped that info to stick.

I am a bit of a newbie, this kind of thing is quite interesting.

gonzogeek


Techone

Check your site and the "device".

Excellent workmanship. Nicely done.

Pedro147

I am in the process of attempting to  build a basic version of the OP's shift register controlled by switches. I am just wondering if the attached schematic of a bistable 555 timer circuit to switch the clock pin of a 74HC595 shift register would be suitable for this project in regard to negating switch bounce. In the original post the OP gave this as the sequence of clock, latch and data pin switching  -

1. latch pin LOW
2. data pin HIGH
3. clock pin LOW
4. data pin {desired pin state for bit N}
5. clock pin HIGH
6. data pin LOW
7. repeat from 3 until N = 8
8. clock pin LOW

I am just wondering why the latch pin does not go HIGH in this sequence, and if this sequence is correct. Thank you Pedro.
http://www.pedroduino.com

dhenry

Quote

Possible to operate a shift register manually with switches?


Yes.

Hippynerd

There was virtual shift register on a website, I found it a few months ago, but cant find it again. Does anyone know where that site was? it was pretty cool, it was just like the manually switched shift register, only it was a website.
https://sites.google.com/site/rgbledcubes

Nick Gammon


Quote

Possible to operate a shift register manually with switches?


Yes.


@dhenry: I wonder if you read the OP's comment on page 1:


... and ... 11 months later :) a manual shift register is born!

http://www.thisisobsolete.com/2012/04/manual-shift-register.html


He's already made one, so telling him it is possible at this late stage is rather pointless.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

Pedro147

Yes, I too found it a perplexing response from dhenry, seemingly directed to the OP when I was the person who was after some advice. Oh well, I managed to work this project out by myself using a 555 timer ( as kindly suggested by several forum members to the OP initially) to trigger the clock pin. If anyone is interested here is a short video of the circuit in operation, Pedro

http://www.youtube.com/watch?v=YbesGontTe0
http://www.pedroduino.com

Pedro147

After getting this circuit to work on the breadboard, I decided to build it up on some veroboard and house it in a small metal enclosure. It was all working perfectly well but the last step was to fit a LM 7805 voltage regulator so I could power it from a 9 volt mains power adapter. Before I fitted the 7805 I was just using the 5 volts from an Arduino.

Prior to taking this last disasterous step whenever I first connected the power, all the LEDS would be off. I would then switch the latch switch, grounding pin 12 of the 595 shift register, then enter the eight bits into the SR using a monostable pulse from a 555 timer into clock pin 11  of the 595, after selecting either a high or low data pin input via a switch to 596 data pin14 (grounded no LED on, + 5 V LED on) After the eight bits were in the SR I would open the latch switch and the selected pattern of LED's would display. Now whenever I first power the circuit up there are some LED's on, and if I quickly connect and disconnect the power, the LED's seem to be moving through the SR at each connect / disconnect action.

As I said prior to trying to fit the power regulator, whenever I first connected the circuit all the LED's would be off. It all still works but you have to leave the SR unlatched with data pin 14 low and clear whatever LED's are on by inputing clock pulses until the SR is empty. Then you can clock in which LED's you want on. I do have an Atmega 328 in the circuit but it is only used to count through the eight clock pulses and display them on a 7 seg. The reset pin 1 of the 328 is only used to set the 7 seg back to zero after the eighth bit is clocked in i.e. prior to entering another eight bits for the next sequence.

I have disconnected the 7805 and the two 10 mf caps to see if somehow whilst fitting them I had changed the circuit that was working but no luck. Also checked all ground connections and that the latch switch was grounding when in the latched position but no problems there.

I have attached the circuit schematics and was wondering if anyone might be able to suggest where I might look for the problem. I am assuming that I have understood the sequence of SR operation correctly, and that this explanation makes some sense,

Thank you Pedro.
http://www.pedroduino.com

Pedro147

Inspired by this project by Jim Harris,
I constructed this manually controlled shift register. It was a great learning exercise and the most complex electronic project that I have attempted so far. Along with learning how to display the clock button presses on a 7 Seg display, I also used a minimal Arduino to control the 7 Seg and a 555 timer to trigger the shift register clock pulse.

http://www.youtube.com/watch?v=gy1caSZ2Ny0

http://www.pedroduino.com

Hippynerd

https://sites.google.com/site/rgbledcubes

Pedro147

http://www.pedroduino.com

Hippynerd

Heh, too slowly, but Im nearing completion on the second cube design, and the others are not too far behind them. Ive spent a bunch of time testing parts, I should post something soon.
https://sites.google.com/site/rgbledcubes

Hippynerd

http://www.youtube.com/watch?v=6fVbJbNPrEU
This guy just posted a similar video, he also has some LED cube videos, and other LED/microcontroller/electronics videos, and blog.
https://sites.google.com/site/rgbledcubes

Pedro147

Thanks for that Hippynerd. Yes I have seen his stuff before. Cluey guy, but can be a bit verbose at times  8)
http://www.pedroduino.com

Go Up