Specifications

HIGH VOLTAGE INTERFACING
CAUTION: When working with high voltages, the potential for fire, explosion, electrocution, eye injury or blindness
and life threatening injuries or death exists. If you are not familiar with the precautions needed when working with
high voltages, do not attempt to connect high voltage up to these circuits. To prevent the danger of a high voltage
feeding back to the ADC-16 and the fire/injury/electrocution hazard caused by an open or short circuit, a 10 volt 5
watt zener diode and 1/4 amp fuse should be connected as shown in figure E. Wire used to interconnect a high
voltage input must be rated for use with the higher voltage. When connecting the ADC-16 to high voltage AC
equipment the method shown in figure D above is recommended.
The following method is used to divide a high voltage down to the 5 volt range needed for input into the ADC-16. This
method involves the use of two resistors (R1 and R2) which together add up to Rt (total resistance). The total
resistance is determined by using the Ohms Law to compute the resistance needed for a 1 milliamp current flow
through the resistors. EXAMPLE: If your full scale voltage is 100 volts (R = E divided by I) 100 volts divided by .001
amp = 100,000 ohms (100K ohm). To determine the proper ratio, divide 5 volts by the full scale voltage. 5 divided by
100 volts = .05. Multiple this ratio by the total resistance to determine the value of R2. R1 is then equal to the
difference between the total resistance and R2. EXAMPLE: ratio .05 times total resistance 100,000 ohms = 5,000
ohms (the value of R2). Total resistance 100,000 ohms less R2 5,000 ohms = 95,000 ohms (the value of R1). To
determine the power rating needed for the resistor, use the following formula: P = I squared times R. EXAMPLE: .001
squared = .000001 times R1 95,000 ohms = .095 watts. A 1/8 or 1/4 watt resistor would be sufficient.
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Fuse or Limiting Resistor (330 ohm 1 watt)
1 Amp Diode (50 volt)
AC Primary Voltage
120, 277, 480 etc.
(-)
6 or 12 Volt
Secondary
100 mf
35 volt
24 ga Communication Cable
To Analog
Input
To Analog
Input
(+)
(-)
10 Volt 5 Watt
Zener Diode
1/4 Amp Fuse
Diode
(+)
High Voltage
AC/D C Input
(-)
Ground for
Safety
R1
R2
(1 ma maximum current
through resistors)
(+)
R1
R2
100 mf
35 volt
+
FIGURE C
FIGURE D
Switch or Relay
Contacts etc.
(Reference +)
To Analog Input
(+)
10 K ohm
(Reference -)
DIGITAL INPUT
(0=OFF)
(255=ON)
FIGURE A
(Reference +)
(Reference -)
To Analog
Input
POTENTIOMETER
MOVEMENT SENSING
FIGURE B
Ref (-)
To Analog Input
Ref (+)
27K Ohm
Cadmium Sulfide
Photo Cell
+
10 mf Tantalum Capacitor
USING AN ANALOG INPUT
FOR ON/OFF STATUS
MEASURING LIGHT LEVELS
FIGURE E
10K OHM
TYPICAL
IMPORTANT: The full scale voltage used should be the highest possible voltage that could be present at the high
voltage input.
AC voltages may be applied to the high voltage input if a diode is connected in series and a filter capacitor (100 mf,
35 volt typical) is connected between the ADC-16 analog input and the ADC-16 reference (-). AC voltages over 24
volts or great enough to create an electrical shock hazard or fire should be connected to the ADC-16 analog input
using a step-down transformer to reduce the high voltage down to the 5 volt range as shown in figure D. A diode and
filter capacitor must be connected on the secondary side of the transformer (a common low current power
transformer may be used).
8 BIT CONTROL SOFTWARE
Analog information is transmitted from the ADC-16 upon receipt of a channel code which must be transmitted by the
computer. The channel code is equal to the channel number - 1. To acquire the analog information on channel 1 the
computer must first transmit a (0). Because of the delay which is required for the 0809 chip on the ADC-16 to make
the conversion, the analog data transmitted will be for the previous channel requested. If information from just one
analog input is desired, it will be necessary for the channel code to be transmitted twice. The data transmitted by the
ADC-16 after the first transmission will be invalid. The following transmission by the ADC-16 will be the analog data
on that channel at the time that the first channel code was received. The data byte transmitted by the ADC-16 will be
a binary number equal to 0 to 255 decimal (0 = 0 voltage at the analog input, 255 = full scale voltage, 128 = half scale
voltage, etc.). The ADC-16 will only recognize channel codes 0 to 15 (or 0 to 31 with the AD-16 or ST-32 connected).
The ADC-16 passes all higher codes to the EX-16 (if connected) for relay control functions.
10 BIT ANALOG INPUTS
The 10 bit option of the ADC-16 functions very similar to its 8 bit counterpart with the exception of the following:
(1) Input voltage range should be maintained at 0 to 5 volts DC (5.0 volts across the voltage reference inputs).
(2) The ADC-16 will transmit in two byte format as opposed to the single byte format of the 8 bit. The first byte
received will be the most significant digits (all eight bits are used). The second byte received will be the least
significant two digits (the first 6 bits will always be zero and are not used).
(3) The sampling rate of the 10 bit version will be less than half that of the 8 bit as a result of the two byte format
of the 10 bit converter (approximately 500 samples per second for a single channel at 19,200 baud).
ADC-8G (ADC-8 port #1 = 10 bit)
ADC-16G (ADC-16 port #1 = 10 bit, port #2 = 8 bit)
ADC-16GH (ADC-16 port #1 = 10 bit, port #2 = 10 bit)
SYSTEMS LEVEL PROGRAMMING CONSIDERATIONS
In Basic and other high level programming languages, the Line Status Register is automatically checked for incoming
and outgoing bytes and handles the data flow as needed. When reading or writing to the COM port registers directly
(such as in Assembly, C or using the OUT command in Basic), it will be necessary to check the Line Status Register
before reading or writing the incoming or outgoing byte.
BEFORE TRANSMITTING.... check BIT 5 of the Line Status Register before sending byte (bit must be high)
BEFORE RECEIVING.... check BIT 0 of the Line Status Register before accepting byte (bit must be high)
I/O PORT REGISTER LOCATIONS FOR THE LINE STATUS REGISTER
COM 1 COM 2 COM 3 COM 4
3FD 2FD 3ED 2ED (hex values)
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