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From: mark@phx.mcd.mot.com (Mark Clayton)
Subject: Re: A sense of balance
Message-ID: <1993Feb3.162747.26434@phx.mcd.mot.com>
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Organization: Motorola Computer Group, Tempe, Az.
References: <1993Jan31.085934.17072@adobe.com> <1993Jan31.161809.7936@sbcs.sunysb.edu>
Date: Wed, 3 Feb 1993 16:27:47 GMT
Lines: 44

In article <1993Jan31.161809.7936@sbcs.sunysb.edu> shane@cs.sunysb.edu (Shane Bouslough) writes:
>
>I have also heard of, but never seen (get this), microprocessor controlled
>carpenter's levels. I'm not sure what they do, but they're supposedly
>hot sellers, and if there is a CPU hooked up to the thing, maybe it's
>possible to use it as a sensor. Hmmm. I'm going to have to look into that.
>
>-Shane

A couple of weeks ago I took apart an electronic carpenter's level.
The level sensor inside the housing is approx. 1 1/4 inches in
diameter and 3/8 of an inch thick.  There are 3 contacts visible on
the sensor (an unknown number hidden underneath).  The sensor seems
to be capacitance based since probing the sensor contacts with a scope
is detected as an error by the micro.

The micro is a house-numbered 68HC05C? variant.  There are RX and TX
pads identified on the PC board.  These are a 9600 baud asynchronous
serial port (0 & 3.5 Volt levels).  There is a simple communications
protocol that allows reading and writing the lower 256 bytes of 
memory, as well as some less obvious operations.  (Details available
on request.)  There are several 16 bit values in low ram that are
mostly proportional to the degree value displayed by the level.

The most or all the micro's I/O is dedicated to driving the LCD display.
I haven't looked at how the sensor and micro communicate.  All the
investigations were done in a weekend and there's lots of unknowns.

The level was a $50.00 (mail order) SmartLevel series 200 with 0.1
degree resolution near horizontal or vertical and 0.5 degrees otherwise.
The level works at any angle. It is somewhat sensitive to horizontal
accelerations, but stablizes quickly.

For those who are interested, I ordered the level from Tool Crib
1-800-358-3096 as part number SL224, series 200, 2 foot level.  The
level manufacturer is, Wedge Innovations, 2040 Fortune Drive,
Suite 102, San Jose, CA 95131, 1-800-762-7853.

Mark
mark@phx.mcd.mot.com

Standard disclaimers: 
No Financial interest ...  No proprietary info ...  Not company policy ...

