From: Steve C. (stevec50_at_yahoo.com)
Date: Sat Jul 20 2002 - 18:43:10 EDT
A different laptop won't help, you will have to use an
external power supply.
Signals on a parallel port are 5 volts but all the
chips in a laptop are low power devices to save the
battery so they won't put out enough power on the pins
to run anything. Older desktop machines had more
robust circuitry and were able to run accessories but
newer ones may not be able to do that either.
Lots of desktop machines had 5 volts tied to some
unused pins on the connector that could be used to
power accessories although laptops probably don't have
that kind of setup and there was no standard for it.
The same is true of serial ports and USB. Serial ports
on a desktop are supposed to put out +/- 12 volt
signals and can withstand 35 volt overloads before
blowing out. Laptops may only put out +5/-0 volts and
blow out at just 15-20 volts.
USB on laptops has the same problem. The port won't
put out enough power to run anything that is more of a
load than a mouse. If you try an external hard drive
that connects to the USB port it won't work on a
laptop but will work on desktops.
--- Dave <iluv2see_at_yahoo.com> wrote:
>
>
> Anybody know if the parallel port voltage on a 2645
> 3AU is 5 Volts or
> something else?.. I'm programming some eeprom chips
> with a cable
> attached via the parallel port... works on 2
> different desktops fine,
> but no go with the laptop... I know this cable
> requires 5 volts to
> operate, so this may be the problem... if this
> laptop is NOT 5 volts,
> would I have to go to an older model to get same? or
> (unthinkable)
> another brand??
>
> Thanks.
>
> Dave
>
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