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[on:]

Hi everyone,
I am doing project using many chips and parallel port to run fan

But the problem , our circuit it doesn't run when we provide the voltage
We didn't use parallel port yet because just we want to test the circuit if it is work?

[Reply #1 on:]

This is the circuit diagram

Wejust use the upper part , means we used just one uln 2803 chip

[Reply #2 on:]

its the black wire thats the problem,

the one  just behind the pink one,

:->

[Reply #3 on:]

Which one do u mean?
The circuit has many wires

[Reply #4 on:]

The last time I checked, Arduinos don't have parallel ports.  Are you certain you are posting your request for help on the correct forum?  Could you have meant your posts for a "PC automation" forum?

[Reply #5 on:]

Please do not cross-post.

[Reply #6 on:]

This IS the "other hardware" party of the forum, though usually we prefer topics to be somewhat Arduino-related...
You could in fact replace the entire circuit up to the ULN chips with an Arduino or AVR chip, simultaneously gaining the ability to operate via USB (and/or get debugging info via USB.)

it doesn't run when we provide the voltage

"doesn't run" how?   What are you doing to it, and how are you expecting it to behave?

You have no bypass caps.
The 74LS05 has open-collector outputs and really isn't well-suited to use as a general purpose inverter.  Though it might work if you're using "real" 74ls series logic, since inputs float high.
It looks like the circuit should toggle the relays when you provide a clock by select/deselect/etc the inputs to the '154, but your circuit isn't providing any toggling.  Doing so by attach/detach of wires will have "bounce" issues.

[Reply #7 on:]

(um, are you working from here: http://xman.postalboard.com/t75-device-switching-using-pcs-parallel-port ?
Or a less detailed source of information?  Maybe their explanation will help (but it doesn't look like a very good explanation to me.)

[Reply #8 on:]

Yes i am working the same project that in the website
http://xman.postalboard.com/t75-device-switching-using-pcs-parallel-port

[Reply #9 on:]

This IS the "other hardware" party of the forum, though usually we prefer topics to be somewhat Arduino-related...
You could in fact replace the entire circuit up to the ULN chips with an Arduino or AVR chip, simultaneously gaining the ability to operate via USB (and/or get debugging info via USB.)

it doesn't run when we provide the voltage

"doesn't run" how?   What are you doing to it, and how are you expecting it to behave?

You have no bypass caps.
The 74LS05 has open-collector outputs and really isn't well-suited to use as a general purpose inverter.  Though it might work if you're using "real" 74ls series logic, since inputs float high.
It looks like the circuit should toggle the relays when you provide a clock by select/deselect/etc the inputs to the '154, but your circuit isn't providing any toggling.  Doing so by attach/detach of wires will have "bounce" issues.

Yes when provide 12v to relay and 5v to other chips that in the circuit diagram
The fan doesn't work

[Reply #10 on:]

The mind boggles.

Yes i am working the same project that in the website
http://xman.postalboard.com/t75-device-switching-using-pcs-parallel-port

Even in 2007 that article was 20 years behind the times. And the code is all left justified and full of s

@Afnan
Do you have a reason to go this way? If you're into having a retro trip or just want to learn about 74-series chips that's OK, but if this is a serious project it's time to get real.

Yes when provide 12v to relay and 5v to other chips that in the circuit diagram
The fan doesn't work

Don't the chips need some control from the PC? Just sayin'

_____
Rob

[Reply #11 on:]

Don't the chips need some control from the PC? Just sayin'

That's the way I read it.  Nothing will happen (aside from possible random startup state) without manipulating the inputs so that the relevant 7474 clocks end up toggling.

[Reply #12 on:]

Hi to everyone,

Please i want to run fan in this circuit using parallel port
Please if anyone suggest to me code to run this circuit


I used 74ls154, 74ls05, 74ls74 and ULN2803
I connected the relay with ULN2803 and connected the fan with relay

So i want to run the fan from the code
If anyone know about that please help me..

[Reply #13 on:]

Kinda tough to see what is going on there since there aren't any labels or schematics.  Without knowing the circuit or having some idea of what you want it to do it's going to be hard to help out, especially with "code" for hardware you might not be using.  Is this going to be connected to an Arduino at some point?

Also, this is the "Other Software Development" board; you might have better luck posting in "General Electronics" or (if you're going to use an Arduino) "Interfacing w/ Software".

[Reply #14 on:]

He doesn't need to post this anywhere else. He's already got a whole thread on it in Other Hardware.

Pete