Hi I need a little help with a little project I want ot build.
I want to build a 4 input selector for a pre amp. I want to use relays to select inputs. I want to use a 4 bit ring counter to do the selection (as in the diagram). Each Q output will be connected to the base of a transistor which will drive a relay. I would use a button to connect the clock input the Vdd (to act as a clock pulse). So each time I press the button the relays would turn on in sequence.
I was thinking that I could use two 74ls74a chips as each chip has two D flip flops and it give access to reset if each Flip flop.
Will this work?
Any suggestions?
I want to build a 4 input selector for a pre amp. I want to use relays to select inputs. I want to use a 4 bit ring counter to do the selection (as in the diagram). Each Q output will be connected to the base of a transistor which will drive a relay. I would use a button to connect the clock input the Vdd (to act as a clock pulse). So each time I press the button the relays would turn on in sequence.
I was thinking that I could use two 74ls74a chips as each chip has two D flip flops and it give access to reset if each Flip flop.
Will this work?
Any suggestions?
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Hi,
It looks to me as if you've made a Johnson binary counter there. The third step will have input 1 an 2 active.
You'll either have to decode with a binary to decimal/ octal decoder (like a 4028), or use a decimal / octal counter (can't remember the number).
There are lots of solutions to the selector question. My favourite is the 74C922 .
Cheers,
It looks to me as if you've made a Johnson binary counter there. The third step will have input 1 an 2 active.
You'll either have to decode with a binary to decimal/ octal decoder (like a 4028), or use a decimal / octal counter (can't remember the number).
There are lots of solutions to the selector question. My favourite is the 74C922 .
Cheers,
Hi thanks for the help so far.
dhaen, the circuuit is a ring counter not a Johnson, here is the web page I got the circuit from: http://www.eelab.usyd.edu.au/digital_tutorial/part2/register07.html
moamps, very nice circuit there, I might just try it.
dhaen, the circuuit is a ring counter not a Johnson, here is the web page I got the circuit from: http://www.eelab.usyd.edu.au/digital_tutorial/part2/register07.html
moamps, very nice circuit there, I might just try it.
hello guys,
This circuit seems to me a little bit impractical, I don't like the idea of cicling thru all unused inputs until I reach the good one. I rather use a circuit with a selection button for every input (4 inputs - 4 selection buttons). This is easy to be done with some flip-flops with set - reset inputs and some diodes. If someone is intersted maybe i'll draw a schematic later.
The idea is that the button for one input should give a command on the set input of one flip-flop and reset the rest of the flip flops.
This circuit seems to me a little bit impractical, I don't like the idea of cicling thru all unused inputs until I reach the good one. I rather use a circuit with a selection button for every input (4 inputs - 4 selection buttons). This is easy to be done with some flip-flops with set - reset inputs and some diodes. If someone is intersted maybe i'll draw a schematic later.
The idea is that the button for one input should give a command on the set input of one flip-flop and reset the rest of the flip flops.
I once built an input selector as originally described here but this is more
than ten years ago, so and I am rusty on this and resurrect this thread:
I am building a DIY CD-Player.
It will be a top loader with a motorized lid.
Transport, system control and decoding
are cannibalized from an old BU-1 based CD Player.
Now I would like to combine the functions of the two two original "Stop" and "Eject" Buttons into one button.
As I cannot hack system control I assume this has to be done in the peripheral by
mimicking the signals from the the original Stop and Eject Buttons tactile switches...?
So the aim is:
You push the combined STOP/EJECT button the first time, the player stops (Stop tactile switch mimicked).
You push it a second time, the lid opens, the third time the lid closes (Eject tactile switch mimicked)
The ring counter resets so that mimicking "Stop" is ready again.
But the 4017 puts out a constant voltage/current, right?
So the virtual tactile switches mimicked by the 4017 behave like they are pressed all the time?
Also pushing any other button like "Play" or "Pause"after pressing "Stop" has to reset the
circuit to prevent the lid from opening as long as "Stop" was not pressed before.
How can this be done and is the 4017 the right device for my task?
All the best,
Salar
than ten years ago, so and I am rusty on this and resurrect this thread:
I am building a DIY CD-Player.
It will be a top loader with a motorized lid.
Transport, system control and decoding
are cannibalized from an old BU-1 based CD Player.
Now I would like to combine the functions of the two two original "Stop" and "Eject" Buttons into one button.
As I cannot hack system control I assume this has to be done in the peripheral by
mimicking the signals from the the original Stop and Eject Buttons tactile switches...?
So the aim is:
You push the combined STOP/EJECT button the first time, the player stops (Stop tactile switch mimicked).
You push it a second time, the lid opens, the third time the lid closes (Eject tactile switch mimicked)
The ring counter resets so that mimicking "Stop" is ready again.
But the 4017 puts out a constant voltage/current, right?
So the virtual tactile switches mimicked by the 4017 behave like they are pressed all the time?
Also pushing any other button like "Play" or "Pause"after pressing "Stop" has to reset the
circuit to prevent the lid from opening as long as "Stop" was not pressed before.
How can this be done and is the 4017 the right device for my task?
All the best,
Salar
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