User's Manual

Radio/Serial Telemetry Module User Manual
Page 16 © March 2000
The internal power supply of the 905 module can supply a maximum 12V load of 700mA. In order
to achieve this, the input power supply must be above 15VAC or 17VDC. Using these figures, it
can be determined whether there is enough supply for more than one module - allow 100mA for
recharging a battery.
For example, assume there is a 905U-01 module and a 105S-01 module at the same location. The
total I/O at the location is 3 analogue inputs, 6 digital inputs and 4 digital outputs. The total load will
be :-
TYPE OF LOAD LOAD mA
905U-01 quiescent 70
105S-01 quiescent 45
6 DI @ 10 mA 60
3 AI @ 20mA x 2 120
4 DO @ 25mA 100
Battery charging 100
TOTAL 495
So both modules could be powered from one power supply and one battery, provided the external
supply voltage is more than 15VAC or 17VDC.
2.3.5 24V Regulated Supply
Each 905 module provides a 24V DC regulated supply for analogue loop power. The supply is
rated at 150mA, and should only be used for analogue loops.
2.4 Input / Output
2.4.1 Digital Inputs (905-1 and 905-2)
The 905-1 and 905-2 modules each provide four digital inputs with 5000 volt opto-isolation,