Patriot UPS to Windows 2000 configuration

I rescued a Patriot UPS from the dumpster. The only problem was a dead battery. I found a battery that was the same size and rating.  After the battery was replaced the UPS started working. This UPS has a "dumb" serial interface. It uses the control lines on the interface to indicate power loss and low battery.
  Windows 2000 has a built-in UPS service. The problem was identifying which pin on the serial interface Windows was monitoring. I searched the web for serial UPS pinouts. I tried a few out on my Win2K box.
  Patriot model SPS450VA BPatriot UPS

Here is the cable pin out

UPS interface DB9 connector pin PC serial port DB9 connector pin
1 shutdown the UPS when this pin is held high for 5 seconds 4 DTR - Held high to shut down the UPS when the computer shuts down
3 normally open switch connects to GND when power fails 8 CTS - When low issues an AC power loss warning
5 normally open switch connects to GND when UPS battery is low 1 DCD - When low initiates computer shut-down
The PC serial port signal RTS (pin 7) is held high. I used this pin to pull-up CTS (pin 8) and DCD(pin1). Connect a 10K ohm resistor from PC serial port RTS ( pin 7) to CTS ( pin 8). Connect another 10K ohm resistor from PC serial port RTS ( pin 7 ) to DCD (pin1). This will pull CTS and DCD high until the UPS closes one of the switches. I bought the 10K resistors and DB9 connectors, male for the UPS and female for the PC at RadioShack. The resistors are connected to the PC DB9 connector. These signal levels do not meet the RS232 design guidelines. It works on my PC, your mileage may vary

Schematic of the UPS cable

cable diagram

Windows 2000 software configuration

In the control panel open Power Options, click on the UPS tab.
Next click the Select Button.
ups power options
Choose Generic for the manufacturer, click on Custom, select the com port the UPS is connected to, and then click the Next button.
Choose the com-port which will connect to the UPS.
Click the Next.
configure a generic ups
Click the negative radio buttons for the Power Fail/On Battery and the Low Battery signal polarity. Then click the Finish button.
configure the radio buttons
Next click the Configure button.
click the configure button
Configure the UPS software response as shown. Then click OK.
configure the time out
Finally Apply the changes by clicking the Apply button. The power management software will begin monitoring the UPS.
apply changes

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