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Coupled Scanning Voltmeter
Near Field Communications
A 10 bit scanning voltmeter with a
Minimum Mass Wireless Coupler, based on
the ATMega8.Range to the Minimum Mass Base Unit is 10 to 15 cm. If the
voltmeter is battery operated, it can be floated from ground.
The basic Minimum Mass Wireless Coupler technology is described and
links to other projects on this site that use the Minimum Mass Wireless
Coupler are located on the web page, Minimum Mass
Download the AVRStudio assembly source for the program: vlfvmtrmg8.asm
Download the AVRStudio assembly source for the include file: vlfcwm8.inc
Schematic of the 4 channel scanning voltmeter. The layout isn't
critical. The 33 uH choke is reduce noise from the controller's
VCC pin on the analog reference voltage.
This project is very simple physically, intended to demonstrate how
easily the Minimum Mass RF Link can be added to a project. The circuit
shown does not have a lot if the nice things that I would usually
include in an instrument, such as the ability to handle out-of-range
input signals without the circuit suffering damage. Therefore, I
suggest that if you build this as a stand-alone instrument, that you
add protection crcuitry to the inputs.
The power suuply is the reference voltage in this case, and the
binary-to-decimal conversion assumes that the refernce voltage is +5
volts, so I sugges that an adjustable regulator be used to obtain a
precise +5 volts. You could use three alkaline cells (for example) in
series, but the calibration would be way off.
The A/D converter setup and binary-to-decmial conversion routines were
taken from the Low Cost Telemetry
on this site. The firmware was created by
taking the Low Cost Telemetry Device firmware, removing the un-needed
code, and adding calls to the Minimum Mass Wireless Coupler drivers
instead of to the USART routines.
Two students at Cornell University incorporated some of these concepts
in their school project. The project as posted at the university
website is very complete and very well written.
Remote Controlled DMM With Minimum Mass Wireless Coupler
Contents ©2005 Richard Cappels All Rights Reserved. http://www.projects.cappels.org/
First posted in March, 2005
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