69 - iRIS 220 / iRIS 320, V1.19 User Guide
13.5 Transistor Switch
On the older iRIS PCB, both digital outputs operate in an
However, another common use for a digital output is to control a sensor such as a pressure transducer. In this case, minimising power consumption is the main aim of the control. The optional transistor switching module inverts the digital output and provides a switched power supply for the transducer or other device. Being solid state, the extra current that a relay coil would draw is eliminated. On the later PCB (V1.2), digital output 1 has the transistor switch incorporated on board and provides a switched 12V supply.
The switch module is a small unit that is able to fit inside the enclosure of an iRIS 320. It has three wires, two of which are terminated with a bootlace ferrule for insertion into the iRIS I/O connector. The third (output) wire has a screw terminal to attach the transducer supply wire. The wires and their functions are as follows:
RED:Supply Voltage In
For sensors requiring a 12V supply, connect this wire to the 12V+ terminal of the iRIS. For higher voltage levels (up to 30V) connect this to the positive lead of a suitable dc power supply and also connect that power supply’s negative lead to the GND terminal or GND terminal of the iRIS.
PURPLE: Switched Output
Connect the transducer (or other load) supply wire to this wire.
GREY: Control
Connect this wire to the appropriate digital output. Normally DO1.
The module has a small red LED that will be illuminated when the digital output is activated.
LED
Switch Module
Red (Supply)
Purple (Output)
Grey (Control)
Figure 17 - Transistor Switch - Module Overview
Switching Module Specification
4K7
Maximum Supply Voltage: | 30V |
Maximum Switching Current: | 300mA |
Lead Length: | 100mm |
2K2
B
Red
E (Supply)
BC327 or equivalent PNP 45V
C 500mA
Grey | Indicator | Purple |
(Control) | ||
| LED | (Output) |
