Using with Campbell Scientific Dataloggers
The cable supplied for use with the COM110 modem is different
from that supplied with older modems. The cable has additional
control wires that are not used in standard Campbell installations.
These are insulated and cut back can covered with insulation at the
free end of the cable.
6.3 Connecting Power
The COM110 modem requires a power supply capable of supplying 5-32V DC, at
an average current of up to 500 mA, with short peak currents of 2.5A (at 5.5 V
supply). COM110 is fitted with a 2A slow acting, fuse in an inline fuse holder in
its power cable, to minimise damage in the event of a failure. Additionally,
Campbell Scientific power supplies include a slow response solid-state automatic
resetting fuse. The normal colour scheme for wiring is RED for positive and
BLACK for negative.
If the COM110 modem is to be powered from the same supply as the datalogger,
ensure that the power connections for the COM110 modem are made as close as
possible to the battery outputs. This will prevent the COM110 modem causing
voltage drops and noise on the supply to the datalogger.
The quiescent power consumption of the COM110 modem is typically around 5
mA, once the unit automatically shuts down at the end of a call. Having the unit
powered all the time ensures unhindered access at any time by remote users and
also avoids complications of having the datalogger program include code to
control the power.
For very low power installations turning the power off may be essential though.
To do this it is possible to control the power supply to the COM110 modem by
using a solid state relay, such as the PSW12 power switch or, if free, to use the
power switch built into the wiring panel of some dataloggers. See Appendix B for
example programs where the datalogger controls power to the COM110. Table 1
shows the wiring from the PSW12 power switch to the datalogger. The failsafe
wire, if connected to 5V, ensure the modem remains powered if the logger
program stops running and the control port the yellow power control wire is
connected to is not driven.
Table 1 COM110 modem Power Supply Connections via a PSW12 switch
COM110 modem Cable Colour
Connection
Red (positive supply)
+ 12V
Black (negative supply)
G
Yellow (power control)
Control Port (or +12V for testing)
White (Failsafe function)
5V (normally)
N.B. These colours and connections only apply to the cable supplied by Campbell
Scientific Ltd.
In the case of CR10X dataloggers, only the power switch in wiring
panels fitted with
green terminal blocks
is suitable.
NOTE
NOTE
15
