IPL EXP I/O Series • Hardware Features and Installation
25
•
Digital I/O digital output with pull-up disabled:
•
When switch 1 closes, the port is on and the front panel LED (IPL EXP RIO8
only) is on.
•
When switch 1 opens, the port is off and the front panel LED (IPL EXP RIO8
only) is off.
•
Example application, digital output without pull-up:
connecting an LED
and an ex5 VDC power source
This application often requires a current-limiting resistor, as shown in the
diagram below. Many button switches that contain LEDs have a resistor built in.
See the guide for the lighted switch or stand-alone LED for details.
NOTE:
Each I/O pin is capable of sinking a maximum of 250 mA.
+
-
+5.0 V
1k ohms
SW 2
SW 1
Digital
I/O
GND
Voltage
Protection
CTL
LED
External
+5 VDC
Power
Source
Resistor
(R)
Figure 14.
Digital I/O Digital Output Application:
LED and Ex5 VDC Power Source Without Pull-up
To determine the value of the current limiting resistor in the circuit shown above,
you need to know the values of three variables:
i
= LED forward current in amps (found in the data sheet for the LED)
V
f
= LED forward voltage drop in volts (found in the data sheet for the LED)
V
s
= supply voltage of the external voltage source
Insert those values into the following equation to determine the resistor value:
R =
V
s
- V
f
i
Example calculation:
i
= 5 mA (0.005 A)
V
f
= 2 V
V
s
= 5 V
NOTE:
If the value calculated for the current limiting resistor is not a
standard resistor value, you can round up the number to the next highest
common resistance value.
The connected LED is off when the port and switch 1 are open.
The connected LED is on when the port and switch 1 are closed.
}
=
5 V - 2 V
0.005 A
=
600 ohms
R =
V
s
- V
f
i
Содержание IP Link IPL EXP 200
Страница 2: ...Safety Instructions...
Страница 6: ......