Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!swrinde!mips!news.cs.indiana.edu!ux1.cso.uiuc.edu!kline
From: kline@ux1.cso.uiuc.edu (Charley Kline)
Newsgroups: sci.electronics
Subject: Re: NEEDED: POWER SUPPLY FOR M68HC11EVB
Keywords: power supply
Message-ID: <1991May29.034654.27632@ux1.cso.uiuc.edu>
Date: 29 May 91 03:46:54 GMT
References: <823@mixcom.COM> <1991May27.170425.744@Eyring.COM> <1991May28.193243.4052@ux1.cso.uiuc.edu>
Distribution: usa
Organization: University of Illinois at Urbana
Lines: 34

I wrote:
>In article <823@mixcom.COM> jjwwjj@mixcom.COM (Robotic Systems) writes:
>The only thing the HC11EVB uses +12 and -12 for is the RS232 line drivers
>and receivers. These are socketed chips; if you pop them out and replace
>them with a MAX232 (or other similar charge-pump-based RS232 driver), you
>will not need the higher voltage supplies at all.

WHOA! Upon re-reading my posting, I realize I gave the incorrect
impression that the MAX232 is pin-compatible with the 1488 and 1489. IT
IS NOT!! You'll have to do more than just replace chips to pull off
this stunt. The MAX232 also requires kinda big external capacitors to
run the charge pump.

Sorry for any confusion. Hope no one fried their EVB after racing right
home and trying out my bad advice.

Also upon re-reading this thread, another poster suggested that a PC
supply would work for this board. Maybe, but do keep in mind that the
68HC11 is a low-power device; the entire EVB only draws a fraction of
an amp.  Switching supplies like those in a PC (and perhaps the
"clicking" supply also mentioned--switchers tend to make odd noises) do
not regulate well at low load and in general, make bad bench supplies.

I thought I had it made when I pulled a VAX-11 memory power supply out
of the trash. 5 volts at FIFTY AMPS! Unfortunately, unless I boiled
some water with a nice fat resistor to draw at least three amps (or so)
from the monster, the five volt regulated output sulked at less than a
volt. Great for a 1979 computer, not so good for me piddling around on
my workbench.

________________________________________________________________________
Charley Kline, KB9FFK, PP-ASEL                          c-kline@uiuc.edu
University of Illinois Computing Services            Packet: kb9ffk@w9yh
1304 W. Springfield Ave, Urbana IL  61801                 (217) 333-3339