Houston Radar SS300 User Manual
Page 17 of 19
Appendix A: Hooking up to the trigger outputs on the radar
The SS300 radar features two “open drain” outputs. The device used for this purpose is the On
Semiconductor relay driver NUD3160. The output configuration of this device is shown below
(from the On Semi datasheet).
The two outputs O/P1 and O/P2 are brought out on the radar connector pins (see IO connector pin
out in manual for connector pin numbers).
This device can sink 130mA of DC current at up to 48VDC (minimum 60VDC breakdown
voltage- do not operate at this breakdown voltage).
However, these are low impedance outputs, which means that you must externally limit the
maximum current that will flow into these outputs to 130mA at the worst-case head voltage. They
may be parallel together to increase this value to 260mA.
There are two ways to ensure this:
1. Connect an output device that is rated to draw no more than 130mA at your supply
voltage (+Vhead). This device can be powered up to 48VDC. For example, this can be a
12 or 24VDC relay coil rated at more than 130 mA coil current or
2. Connect an external resistor in series with the output load and the O/P1 or O/P2 pins. The
value of this external resistor should be calculated as follows (ohms law):
R (in K Ohms)= (Vhead –Vload drop)/130
Load rated to draw
max of 130mA at
+Vhead max
+Vhead
Load
+Vhead
Resistor
Load
Method 1
Load
Method 2
