ADC0808 – Simple Analoque to Digital Converter

ADC0808 – Simple Analoque to Digital Converter

This is a very simple analoque to digital converter circuit based on 8-bit analog-to-digital converter ADC0808. Typically analogue-to-digital converter (A/D Converter / ADC) requires interfacing through a microprocessor to convert analogue information into digital format. This needs extra hardware and appropriate software, resulting in more complexity and hence the total amount of cost.

The circuit of Analogue to Digital converter shown here is configured around ADC0808, getting rid of the utilization of a microprocessor. The ADC0808 is definitely an 8-bit A/D converter, that has data output lines D0-D7. It operates on the principle of successive approximation. It features a total of eight analogue input channels, out of which any one can be chosen working with address lines A, B and C. Right here, in this case, input channel IN0 is chosen by grounding A, B and C address lines.

Typically the control signals ALE (address latch enable), EOC (end of conversion), OE (output enable) and SC (start conversion) are interfaced by means of a microprocessor. Even so, the circuit shown
right here is constructed to operate in its continuous mode without working with any microprocessor. Therefore the input control signals ALE and OE, getting active-high, are tied to Vcc (+5 volts). The input control signal SC, getting active-low, initiates start of conversion at falling edge of the pulse, whereas the output signal EOC becomes high after completion of conversion (digitisation). This EOC output is coupled to SC input, where falling edge of EOC output acts as SC input to direct the ADC to begin the subsequent conversion.

Since the conversion starts, EOC signal goes high. At next clock pulse EOC output again goes low, and hence SC is enabled to get started on the next conversion. Thus, it delivers continuous 8-bit digital output corresponding to instantaneous value of analogue input. The optimum level of analogue input voltage ought to be properly scaled down below positive reference (+5V) level.

The ADC0808 IC needs clock signal of normally 550 kHz, which can be simply produced from an astable multivibrator constructed applying 7404 inverter gates. In order to visualise the digital output, the row of eight LEDs (LED1 through LED8) have been utilized, wherein every single LED is connected to respective data output lines D0 through D7. Considering that A/D Converter runs in the continuous mode, it shows digital output as soon as analogue input is applied. The decimal equivalent digital output value D for a provided analogue input voltage Vin can be calculated from below relationship:

D = Vin/Vref * 256

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ADC0808 Datasheet:

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