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---+ Analogue to Digital and Digital to Analogue Conversion The [[http://www.nxp.com/documents/data_sheet/PCF8591.pdf][PCF8591]] is a 4 channel analogue to digital (ADC) and 1 channel digital to analogue converter (DAC). ADC and DAC have 8 bit resolution. The PCB card already contains 3 devices that can be connected via jumpers to the ADC inputs:<br /><br /> * a potentiometer on channel 0 * a photo resistor on channel 1 * a thermistor on channel 2 * channel 3 is free The sensors are resistors whose resistivity changes with the parameter to be measured (temperature or light intensity) and, in conjunction with a 1 kΩ resistor they implement a voltage divider. This voltage is converted to a digital value by the ADC. I used the forth channel to feed back the DAC output. | <img alt="pcf8591front.png" height="306" src="%ATTACHURL%/pcf8591front.png" title="pcf8591front.png" width="458" /> | <img alt="pcf8591back.png" height="306" src="%ATTACHURL%/pcf8591back.png" title="pcf8591back.png" width="458" /> | | pcf8591 front | pcf8591 back | You can distinguish the PCF8591 chip, the potentiometer and the photo resistor and thermistor. The pins on the left make the connections to external analogue signals and 1 pin provides the DAC output while the pins on the right implement the I2C interface with SCL, SDA, Vcc and Gnd. -- %USERSIG{UliRaich - 2017-02-01}% ---++ Comments %COMMENT%
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Topic revision: r2 - 2017-02-04
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