Wireless Coupled Scanning Voltmeter (ATMega8)

  
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. 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 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 Wireless Coupler.
Wireless Coupled Scanning Voltmeter (ATMega8) - schematic

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. 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. The A/D converter setup and binary-to-decmial conversion routines were taken from the Low Cost Telemetry Device project 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.



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