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0821-2451-3075 (Hp/WA)
021-8839-3519 (Telp/Fax)
muhtadirkadir@yahoo.com(Email)
KONVERTER ANALOG to DIGITAL
1. Background Conversion of Analog to Digital
Internal operation of digital systems always use a binary or multiple types of binary code, as well as any input or input into a digital system must also be in binary format sebelam processed in digital circuits, so does the output (output) as the result of a process of digital circuits is also in the form of binary.
Hence the need of digital control system is using analog transducers on the input or the input side and the output side of the analog drive or output, as illustrated in Figure 39.
In image 39 inputs or input is analog scale obtained from the process in trasduser, then by the analog to digital converter (ADC) is converted into a digital scale. The digital scale is an input or input of a digital system for processing in arithmetic or logic to produce a digital scale. Therefore, the output or output of a digital system in the form of a digital scale, while it takes to move the next circuit is analog scale, the device is required analog to digital converter which serves to convert digital scale from the process into analog scale for example to control a dc motor speed dibutuhan anlog scale.
So that we can see the existence of an interface in the form of ADC and DAC in a digital circuit system (computer, microprocessor etc.) With the analog world, here shows us that a control system is possible combination of two quantities, namely analog and digital where the system's sensor is analog , with digital processes and the prime mover as the output is analog scale.
Figure 39. The digital control system
2. ADC (Analog to Digital Converter)
Analog to Digital Converter (ADC) is a tool designed to convert analog signals into signals - digital signal. For example IC ADC 0804, can meet the needs of the circuit to be created. This type IC work closely with adding a bit components in accordance with the specifications that should be given and can quickly convert an input voltage. The things that also need to be considered in the use of this ADC is the maximum voltage that can be converted by the ADC of the signal conditioning circuit, resolution, external timer ADC, the type of output, accuracy and conversion time.
Some important characteristics of ADC:
1. Conversion time
2. Resolution
3. Nonlinearity
4. Accuracy
There are many ways that can be used to convert the analog signal into a digital signal whose value is proportional. ADC type commonly used in the design is a kind of successive approximation Conversion or multilevel approach that has a conversion time is much shorter and does not depend on the value of the input analog signal to be converted or
1. Conversion time
2. Resolution
3. Nonlinearity
4. Accuracy
There are many ways that can be used to convert the analog signal into a digital signal whose value is proportional. ADC type commonly used in the design is a kind of successive approximation Conversion or multilevel approach that has a conversion time is much shorter and does not depend on the value of the input analog signal to be converted or
• In Figure 1 shows a block diagram of the ADC.
Figure 1. Block diagram of the ADC
• In short, the working principle of the converter A / D is all the bits set and then tested, and where necessary in accordance with predetermined conditions. With the fastest circuit, the conversion will be completed after 8 clock, and the output D / A is an analog value equivalent to the value of the register SAR. If the conversion has been carried out, a series of re-send the completed conversion logic signal low. Down side of this signal will produce an equivalent digital data into the buffer registers. Thus, the digital output will remain stored even will start a new conversion cycle.
ADC IC 0804 has two analog inputs, Vin (+) and Vin (-), so it can accept differential input. Actual analog input (Vin) equal to the difference between the voltages associated with the two input pins that Vin = Vin (+) - Vin (-). If the analog input in the form of a single voltage, this voltage should be connected to Vin (+), while Vin (-) digroundkan. For normal operation, the ADC 0804 using Vcc = +5 volts as a reference voltage. In this case the analog input range from 0 volts to 5 volts (full scale), because this IC is SAC 8-bit, the resolution will be equal to
• ADC IC 0804 has two analog inputs, Vin (+) and Vin (-), so it can accept differential input. Actual analog input (Vin) equal to the difference between the voltages associated with the two input pins that Vin = Vin (+) - Vin (-). If the analog input in the form of a single voltage, this voltage should be connected to Vin (+), while Vin (-) digroundkan. For normal operation, the ADC 0804 using Vcc = +5 volts as a reference voltage. In this case the analog input range from 0 volts to 5 volts (full scale), because this IC is SAC 8-bit, the resolution will be equal to
(N states the number of bits of binary outputs an analog to digital converter ICs) IC ADC clock generator intenal 0804 has to be activated by connecting an external resistor (R) between pin CLK and CLK OUT IN and an external capacitor (C) between CLK IN and ground digital.
clock frequency obtained at pin CLK OUT equal to:
clock frequency obtained at pin CLK OUT equal to:
For this clock signal can also use an external signal connected to the CLK pin IN. ADC 0804 having an 8 digital outputs that can be directly linked to the data channel microcomputers. Put (chip select, active low) is used to enable the ADC 0804. If a high logic, ADC 0804 is off (disable) and all keluaranberada in a high impedance state.
Put (write or start convertion) is used to start the conversion process. For it must be logic 0. The output pulse (interrupt or end of Conversion) declared the end of conversion. At the time of starting the conversion, will change to logic 1. At the end of the conversion will return to logic 0.
ADC0804 Operation Mode
1. Continuous operation mode (free running)
For ADC0804 can be operated in continuous operation mode (continuous reading process and without surgery handshake process), then the CS and RD-mounted earthed, while the WR and INTR-mounted not connected anywhere. The working principle of continuous operation is that the ADC will start a conversion when INTR back inactive (logic '1'). Once the conversion process is complete, INTR will be active (logic '0'). To start the first conversion WR must be earthed in advance, it is used to reset the SAR. However, the subsequent conversion to reset the SAR can use the INTR signal when active (logic '0') and start conversion when inactive (logic '1').
1. Continuous operation mode (free running)
For ADC0804 can be operated in continuous operation mode (continuous reading process and without surgery handshake process), then the CS and RD-mounted earthed, while the WR and INTR-mounted not connected anywhere. The working principle of continuous operation is that the ADC will start a conversion when INTR back inactive (logic '1'). Once the conversion process is complete, INTR will be active (logic '0'). To start the first conversion WR must be earthed in advance, it is used to reset the SAR. However, the subsequent conversion to reset the SAR can use the INTR signal when active (logic '0') and start conversion when inactive (logic '1').
When the conversion is completed the data conversion result will be issued directly from the buffer to be read as RD grounded. When the INTR signal is active, this signal is used to reset the SAR. When INTR back inactive (logic '1') the conversion process begins again.
0804 free running ADC circuit is shown in Figure
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