Re: need help to build a card for driving 17 relays
- Look in the "Files" section of this group for a PDF
document "parallel.pdf" along with PDF data sheets for most of the
components required. This describes a simple interface for sending
and receiving data via the parallel port. It doesn't cost too much
and takes about an afternoon to build. You'll notice that not all 8
bits of the control signal are used. You can use the unused bits to
control additional IC's (look at the schematic to see how each IC is
addressed). Depending upon your relays you may be able to drive them
directly from the circuit given. The only caution is that you'll have
to read the values from the sensors a bit at a time so if the values
are rapidly changing it might present a minor problem. It also
depends upon the resolution of the sensor (binary, 4-bit, 8-bit etc.)
The programming is also described; you can used most popular
programming languages including Java to access the parallel port. You
can also use an old PC that has been discarded for experimentation.
--- In firstname.lastname@example.org, "SADI Kheir-Eddine"
> hi,and return
> well, i need to build an electronic card to drive 17 relays by pc
> two values read from 2 sensors.
> could any body help me please?
well, the real application of that project isn't to drive 17 relays
but to drive 17 electromagnets to simulate a punched card, the
photocell is used to determine if the reader is reading the card or
not. I think that the electromagnet can't function for a long time
without taking a pause then i am planing to use a triger so that when
the photocell's signal is moving from high to low, the electromagnets
will be turned off and when it's moving from low to high, the
electromagnets gets activated. what do you think about it? about the
current sensor i think it's no more needed cuz we'll know if the
reader is on or off by adding a timeout to the photocell, when it's
reached the reader is considered as of until it sends that signal.
then the pc will send 3 bytes containing wich electromagnets to
activate and the board will send 1bit (in 1 byte) wich is sent when
the photocell changes it's state and is used to synchronize between
the pc and the reader. I'll write the software part.
What do you think about all that? am i missing some thing?