Re: Electronics question

[Stephen McGarry <Selfbuild@xxxxxxxxxxxxxxx>]

Butcher a USB cable and use the Red and Black wires (double check with
a meter). Red to the output of the 7805
(bypassing it) and black to GND. The DTR would only be able to source a few
10s of mA so the USB will have plenty of
current (100mA min).
The 7805 was only necessary because a standard RS232 should produce upto
12V.
This will save on a PSU and would be the same GND.

HTH
Stephen

Kevin Hawkins wrote:
>
>
>
> Could it be anything as simple as some configuration parameters for
the
> specific Avocent port in use that causes the port to assert DTR ? 3.5V
> is not a large enough voltage here to work with most RS232 equipment
> -and obviously isn't enough to power a 5V regulator. The port was
> 'open' when you made this measurement I assume.
>
> Ant's suggestions is neat way around this - albeit requiring a
secondary
> PSU.
>
> K
>
> ant wrote:
>  > Hi Paul,
>  >
>  > Yeah you're pretty much there:
>  >
>  > 1) disconnect the DTR line from your circuit (belt and braces)
>  > 2) connect the +ve wire from a 9v DC PSU to pin 1 of the 78L05
>  > 3) connect the ground wire from the 9v DC PSU to one of the
>  > regulator's ground pins (I can't read the schematic, there might
only
>  > be one ground pin, depends on the package)
>  > 4) leave the RXD and GROUND connections to the serial port
>  >
>  > cheers
>  >
>  > ant
>  >
>  >
>  > ------------------------------------
>  >
>  > Yahoo! Groups Links
>  >
>  >
>  >
>  >
>  >
>
>
>
>
>
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