[SOLVED] Help needed for switching on a small project

[shafeey]

HI, I am new to Digital Logic, and totally uninitiated with its practical side. I am trying out a little game project, actually this will be my first.

I have a row of LED, and only one player in that row( represented by a glowing LED), who will move sideways. The player always start at the middle of the row, and cannot get out of the row... So i used a 8-bit shift register which will load a predefined data value when the game is started or a reset button is pushed. For that I have to send HIGH to both S0 and S1 pin of the register only once in the beginning. Then both S0 and S1 pin will be in LOW state. An user controls the player with two buttons, which sends HIGH to either of the pins, but never to both at the same time. I have worked out the logic. But got stuck in the actual implementation with the buttons part.

When the Button is in disconnected state the pins don't get LOW, rather it's undetermined value in my proteus simulation. So the gates all act abruptly. So my question is, does this gets fixed when i put it in a breadboard? I mean in theory not having a high voltage is low, isn't it? Or do I have to use other componenets to get around the problem. I don't know much about the hardwares or the difficulties faced. So can anyone give me a brief idea of what happens in practical circuit, or any workaround?

I have included an image of my simulation...

 

[john blue]

Hi,


Can you pose the .dsn file?

 

[zeroskj1988]

appreciate your effort.in my knowledge no input is given means the input pin will be in high impedance state.if you are not quite sure then you can use pull up resistor

 

[shafeey]

Thanks for the replies... I have made a little more progress on the design, I used LOGICTOGGLE components in proteus so the simulation runs correctly. And I didn't know there are SPDT push buttons, which solves my problems. I think I will build it first with regular buttons and then if it doesn't work, replace them with SPDT. That will probably work, right?

So here's my current design. what do you think about it?

 

[john blue]

Thanks for the replies... I have made a little more progress on the design, I used LOGICTOGGLE components in proteus so the simulation runs correctly. And I didn't know there are SPDT push buttons, which solves my problems. I think I will build it first with regular buttons and then if it doesn't work, replace them with SPDT. That will probably work, right?

So here's my current design. what do you think about it?

You will just have to pull them low with a resistor, then your circuit will have defined states

---------- Post added at 06:27 ---------- Previous post was at 06:14 ----------

 

[shafeey]

Thanks. it's so simple! feeling kind of silly now...