Figure 2-2. Sc-2060 Power Circuit; Figure 2-3. Onboard Equivalent Circuit - National Instruments SC-206 Series User Manual

SC-2060 Board
The 26-pin connector (J1) attaches to the appropriate SC-205X Series board via a 26-pin conductor
cable. You can connect an external +5 V power supply to the external power screw terminal block (J2)
if required. To determine if an external +5 V supply is necessary, refer to Internal or External Power
Selection in Chapter 5. Switch S1 selects either internal or external power. The buffer improves the
logic levels of the outputs from the optocouplers to the host data acquisition board. The optocouplers
isolate digital input signals connected to screw terminals IN0 through IN7 (on J3 through J10) from the
computer. The Vcc terminal of each pair (J3 through J10) of the contacts connects to the power
reference (Vcc) for the digital signal at the corresponding INx, where x represents any channel number
from zero through seven.
The digital input circuitry is positive logic; that is, a high input signal produces a high input state at the
host data acquisition board. The SC-2060 has eight channels of optocoupler input. For each channel,
the digital signal must connect to the channel screw terminals along with its voltage reference signal
(Vcc). The SC-2060 accepts many types of digital signals, including TTL, CMOS logic, and even
voltage references other than +5 V. However, the SC-2060 input circuitry must not carry more than 20
mA (that is, the difference between the voltage reference and the input signal at the terminals must not
exceed 8.4 V) to avoid damage to the board. You can add additional resistance in series with the input
circuitry to keep the current below 20 mA for voltage differences greater than 8.4 V. Figure 2-2 shows
the 5 V power circuit for the SC-2060 board. Figure 2-3 shows an equivalent circuit for the input
channels.
J2
5 V
GND
External
Power
DIO
X
TO J1
(DAQ Board)
SC-206X Series User Manual
F2
0.5 A
0.5 A
F1
From DAQ Board Connector (J1)
Conn 5 V

Figure 2-2. SC-2060 Power Circuit

+5 V
L5541
4.7 k
20
Y
X
A
X
10
HCPL-2611-060

Figure 2-3. Onboard Equivalent Circuit

2-2
1
EXT
2
IN4001
3
INT
Jumper
S1
IN4148
1/4 W
Ω
300
Opto-coupler
© National Instruments Corporation
Chapter 2
+5 V
D2
1 K
J3 through J10
IN4148
+V ccx
IN x
I
IL