hi..

i ve just started trying out electronics with the parallel port programming with VB...i thought this board might be able to help me out .correct me if i go wrong anywhere ...

so the parallel port has 8 outputs...and i connect that to a pc relay card...

now i need to connect to more than 8 different outputs...ideally by a timer ..
is it possible to have more than 8 outputs?would it wrok if i used shift registers(or a series of flip flops) for a timing circuit ?

thnx..

Yes it is possible to make the 8 outputs into more than 8. What do you need more than 8 outputs for? you might want to try something like demultiplexing.

with demultiplexing, you can have take a small numer of inputs and turn it into a larger output.
Basically you have your data input X. Your cable select lines S. and your outputs Y. The cable select
Determines which output line the input bit will come out on.
00 = y0
01 = y1
10 = y2
11 = y3

s+1(for the data) number inputs will equal s^2 number outputs. and if you cant find chips with enough outputs you can always double them up and use enables and such.

Would this method work for your project or not?

ya thnx sinetific ,this is probably what i could use as an input...

but i needed >8 outputs to connect to well more than 8 LED's ..its just a test...if i figure out the usage with multiple outputs...i can plan out better...

i was thinking this output limited to 8 might be a prob.... but u say it isnt.... fine..

few Q's
1.can i use say ...two for input, 6 for output at the same time ?

2. will something like this work ...

- input from parallel port to 9 ouput led's
- since all inputs are given thru the same input,what kind of circuit shud i use to continiously switch this input to consecutive outputs..
do ihave any ohter option ?...

u get the idea rite !

thnx...

No i don't say it's not a problem. I have no idea what your trying to do. oyu need to give me the bigger picture of what your making so I can get a proper idea of what you will need. and no i dont really get the idea fromy our broken english and bad grammer.

pssst, he's making a light to show off to his friends...

all right ppl...

its not exactly a haloween spoof im trying if thats what gizmo was trying to 'hint' .

i 'm trying to connect my parallel port to multiple seven segment displays...

that looks like this
in case ur thinking what kind of seven segment display it is ....


so each of the inputs would go to each side..
so if i wanna make the number '5'
id go for the inputs
a->1, f->1 ,
g->1 , c->1 ,d->1

i want ...say 5 of these individual displays...so that i can use this as a mini display ! thats why i need so many ouputs,the prob is that i have only 1 source of input - the parallel port...so how do i manage the flow of inputs... do i use a flip flop/shift register to pass the flow to next display?

say i wanna pass the number : 12345 (assume ther 5 seven segment displays)

after displaying the first seven segment display , u need to move to the next display automatically till all 5 are displayed ...

now...where were we ...

ok smartass, we all know what 7 segment displays are. Anyways use 3 demultiplexers (2 and 1/2 you might as well just make it six displays it will be just as easy.) and some flipflops to hold the data. Then your code will be 8 bits long to make one segment display. which will be something like
1 \
0 > Cable select
1 /
1 > enable demux1
0 > enable demux2
0 > enable demux3
1 > data
0 > unused bit.(probably use it for clear for the flip flops)

Anyways here is a brief example (I didnt put any of the flipflops in).


If you want me to make the schematic for you. Just tell me. There are probably about ten other ways of doing this. this is the way I came up with if anyone else has any suggestions feel free.

1)buddy ,what circuit simulation software do u use dude, i think i'll find it vvvvery handy...looks nice and neat..thnx.


2)can u verify if this is the implementation uve given above:
- we have the multi level demux's, which lead to the 7seg inputs...
and what exactly is the schematic ?


3)and buddy,correct me if im wrong ...
shud The input from pll port shud flow thru a counter ,so that only after first 7seg is activated; it goes to second one ;and so on ? how else can u do it ?


cheers...

Yeah, that isn't really the schematic for the circuit, but rather just a rough sketch of the idea. If you look closely you can see many errors. I just wnated to show you the idea of how you can have the select go to all 3 demux's and use enable/disable to choose which one will get the data. That wouldnt even come close to working. The software is multisim circuit design and emulator.I was thinking you would be controlling timing with the software. the timing delays between ICs will be in microseconds. Im not the best circuit designer, but im working on it.

heheh...with that type of setup, only one segment of each 7 segment display could be lit up at once. not a problem, you'd just have to cycle through constantly. so, to keep it above 50 - 60 Hz (which is where our eye's can handle flicker without being annoying), and have 8,8,8,8,8, you would need to update 49 segments once every 1/50 of a second. that would mean or, do an update every 1/2450th of a second, or 408us. the parallel port could easily do this, but, there are easier ways.

There are chips made for 7 segment displays. The input side takes a binary number. The output side connects directly to the 7 segment display. when you feed the ic a binary number, it will light up the display with that number. all i've seen even support 7.5 segment displays (the ones that include the period after the number.