User`s manual

XP8000 Series (PLCBus
TM
) Z-World 530-757-3737 9
The DAC2 board’s main power supply (U9) provides +15V up to
1 amp. U8 and U2 provide V–, a regulated –5V up to 50 mA.
U13, an LT1021 (the factory setting) provides a precision 10V
reference (REF–). Optionally, you may install an LT1019 for
U13. This provides a precision 2.5V reference for REF–. A third
option is to leave U13 vacant and install a zener diode at Z1.
The actual reference voltage depends on the sizes of Z1 and R4.
External Connection
Analog signals (voltage or current output) leave the DAC2
board via terminals 1 and 3 on header H1. Other terminals pro-
vide access to board voltages.
H1
VI2
GND
VI1
GND
VCC
V–
V+
+V
When used with most Z-World controllers, the +V (normally
+24V) from the PLCBus is the power source, accessible on H1.
When using the DAC2 board with some controllers, +24V is not
available from the PLCBus. You must supply +24V on H1.
Jumpers
The DAC2 board uses 3 jumpers, J1 through J3. Settings for J3,
coupled with the encoding of the PAL chip U7, determine the
board’s PLCBus address. These settings are explained later.
Jumpers J1 and J2 determine the mode of output channels 1 and
2 (VI1 and VI2, on H1). Connecting pins 2-3 selects voltage out-
put. Connecting pins 1-2 selects current output:
J2
Voltage out
1
J1
Current out
1
Voltage out Current out
11
LED
The DAC2 board has an LED (D1) which illuminates whenever
the board’s address is placed on the PLCBus.
Reset
The DAC2 board has a reset device, U12, that monitors VCC.
Whenever VCC is interrupted, U12 pulls /RST low. Thus, you
can force the board to reset with software or a push-button.
The Circuitry
The DAC2 board’s digital-to-analog circuitry comprises two 12-
bit AD7543s, U3 and U4, and an LM324N quad op-amp chip, U1.
The outputs of the DACs are amplified, providing either current
output or voltage output. The outputs appear at jumpers J1 and
J2 as well as at header H1. Digital input values come, via the
PLCBus, from the program running on the controller.
+
–
+
–
+
–
V+
V–
U1
DAC
OUT
REF
–
V+
V–
V+
V–
330p
RX
10
100K
100K
2.2K
U1
I1
Voltage
V1
(RP1)
J1 or J2
Current
(RP2)
2.2K
(RP1)
(RP2)
U3 or U4
AD7543
Capacitors C7 and C8 are normally not installed. For applica-
tions that operate at more than ~100 Hz, install C7 and C8.
The AD7543 Chip
Each of the two AD7543s receives serial data in register A.
When register A is full, its contents are transferred to register
B. The data are then converted and analog level is output.
Load Register (B)
12-Bit Shift Reg (A)
AD7543
12-Bit D/A Converter
REF
–
LD
STB
OUT
SDI
Each AD7543 has a linearity of ±1 LSB and a gain stability of
approximately 5 ppm per °C.
The output of each DAC is given by the following formula:
OUT =
–
(input / 4096) × REF–
The DAC output voltage ranges from 0 to REF–. When U13 is
an LT1021 (the factory default) REF– is 10V.
Voltage Output
When voltage output is selected, the output is given by the fol-
lowing formula:
V = OUT × (1 + RP2 / RP1)
where OUT is the output of the DAC chip. Output values can be
changed by changing resistor packs RP1 and RP2. The maxi-
mum output voltage is limited by the op-amp to 14V.
Current Output
When current output is selected, the output is given by the fol-
lowing formula:
I = (OUT / RX) × (RP2 / RP1)
Output values can be changed by changing resistor packs RP1
and RP2. The maximum output current is limited by the op-amp
to 22 mA.
How to Use a DAC2 Board
Generally, this is what you do:
1 Initially, send a reset command to the PLCBus.
2 Place the address of the DAC2 board on the PLCBus.
3 Send data to one of the DAC2 board’s two DACs (register A).
When register A is filled, transfer the data to DAC2 register
B where it is converted and output. There is software that
does this.
4 Use the analog output (to control motors, attenuators or
other analog devices).
Addressing the board
Up to 64 DAC2 boards may be addressed individually over a
single PLCBus. The address of a particular DAC2 board is deter-
mined (1) by the encoding of PAL chip U7 installed on the
board and (2) by jumper J3.