LED digital Voltmeter

Posted on Dec 8, 2012

This is an easy to build, but nevertheless very accurate and useful digital voltmeter. It has been designed as a panel meter and can be used in DC power supplies or anywhere else it is necessary to have an accurate indication of the voltage present. The circuit employs the ADC (Analogue to Digital Converter) I.C. CL7107 made by INTERSIL. This IC incorporates in a 40 pin case all the circuitry necessary to convert an analogue signal to digital and can drive a series of four seven segment LED displays directly. The circuits built into the IC are an analogue to digital converter, a comparator, a clock, a decoder and a seven segment LED display driver. The circuit as it is described here can display any DC voltage in the range of 0-1999 Volts.

LED digital Voltmeter
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Technical Specifications - Characteristics Supply Voltage: ............. +/- 5 V (Symmetrical) Power requirements: ..... 200 mA (maximum) Measuring range: .......... +/- 0-1,999 VDC in four ranges Accuracy: ....................... 0.1 % FEATURES - Small size - Easy construction - Low cost. - Simple adjustment. - Easy to read from a distance. - Few external components. How it Works In order to understand the principle of operation of the circuit it is necessary to explain how the ADC IC works. This IC has the following very important features: - Great accuracy. - It is not affected by noise. - No need for a sample and hold circuit. - It has a built-in clock. - It has no need for high accuracy external components. An Analogue to Digital Converter, (ADC from now on) is better known as a dual slope converter or integrating converter. This type of converter is generally preferred over other types as it offers accuracy, simplicity in design and a relative indifference to noise which makes it very reliable. The operation of the circuit is better understood if it is described in two stages. During the first stage and for a given period the input voltage is integrated, and in the output of the integrator at the end of this period, there is a voltage which is directly proportional to the input voltage. At the end of the preset period the integrator is fed with an internal reference voltage and the...

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