SmarTek Cabinet CWD and PRM

The Cabinet Watchdog (CWD) is used to provide cabinet voltage measurements and watchdog services. The CDW can sample up to 4 different DC analog voltages (0 to 25.6 VDC). The sample rate for each channel is 10 samples per second and is averaged to 1 sample per second. The CWD can sample 2 opto-isolated relay inputs (5 VDC to 24 VDC) and 6 TTL level inputs. The sample rate for the digital channels is 10 samples per second. The states of the digital inputs are accumulated for 1 second and the majority is used to determine the on or off state at a 1 sample per second rate. The CWD has 2 opto-isolated relay outputs for driving external mechanical relays. These relays can be used with the Power Relay Module to control cabinet power. The output relays are open collector, and can sink up to 30 milliamps with a maximum collector voltage of 30 volts. In Polled Mode, the CWD provides a watchdog function and expects to receive at least 1 polling request every 20 minutes. If the request is not received, the opto-isolated relay outputs are activated (active low) in sequence and held active for 10 seconds.

The Power Relay Module (PRM) is used to distribute power and provide protective fuses for the battery and cabinet power busses. It also has a mechanical relay which maybe controlled by the Cabinet Watchdog for cabinet reset or similar functions. The main power distribution path is through the normally closed relay.

Cabinet WatchDog

- Size ... 4.5"x 1.25"x0.5"
- Operating Temperature ... -55 deg C to 125 deg C
- Input Voltage ... 9 to 24 VDC
- Required Power ... 135 mw
- Baud Rate ... 9.6 Kbps - 115.2 Kbps
- Communication ... Polled or Periodic