[oopic] Re: Finally got OOPIC working and LCD: Now new questions...

I was not reading carefully and now see about the 2k resistor as well
as the 22k. I assume the 22k creates a high impedance so that the
OOPIC line does not run away with current? What does the 2k resistor
do?

--- In oopic@yahoogroups.com, "rtstofer" <rstofer@...> wrote:
>
> --- In oopic@yahoogroups.com, "jeffkaypic" <jeffkaypic@> wrote:
> >
> > Okay, got my OOPIC working with 4X20 LCD. Next I need to know how to
> > integrate a voltage reading from an I/O line. I need to read one
> > voltage that is between 0-5vdc and another that is 0-60vdc. I see the
> > object to do this but wonder about how to hook up the signal/hardware
> > and how to create a string from the periodic reading of the line into
> > a decimal I can send to the display. If you have links, great, I am
> > not a very accomplished programmer. Thanks,
> >
> > Jeff K. Burbank, CA
>
> Do you want to MEASURE the voltage or just DETECT it. To MEASURE it,
> run it through an 22k resistor in series with a 2k resistor to ground
> and measure the voltage across the 2k resistor. Now, that assumes
> that the voltage can NEVER be more than 60V. The other thing you can
> do is put a Schottky diode between the top of the 2k resistor (where
> it joins the 22k resistor and the input pin) and the 5V power supply
> to dump the excess voltage. The diode is oriented with the BAR end
> toward the 5V supply so it forward biases (turns on) when the voltage
> at the top of the 2k resistor reaches 5.2V To MEASURE the voltage,
> run it into an A/D input and use the oA2D object.
>
> If you want to DETECT it you can divide it as above and run it into
> and IOLine and use oDIO. But, if detection is the goal, you should
> consider an opto isolator instead of a set of resistors. Post back on
> which you want to do.
>
> >
> > P.S. I am now using a USB to serial cable with my XP computer. I am
> > using vers. 6 software. I will eventually want to connect to the
> > parallel programming port because my application (not robot) will be
> > connected to the RS-232 serial all the time. So, since my computer
> > has no parallel port, is there any trick for this?
>
> Yup! All you have to do is buy an obsolete computer with a REAL
> parallel port. Not exactly what you want to hear but that's the way
it is.
>
> You can't even stuff an after-market parallel port in the computer
> because most of the PCI stuff doesn't wind up at the proper address
> for a real parallel port. You need an ISA port.
>
> For what it's worth, www.overstock.com has refurbished 3 GHz Dell
> computers with real ports, a smallish disk, 512 MB RAM and WinXP for
> about $352 delivered.
>
> Richard
>

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