When Circuit Specialists moved to our new building in Tempe, AZ we noticed our communications closet was getting a bit warmer than we wanted it to be. Rather than spending the time and money needed to route an air conditioning duct into the closet, we decided that just getting some air from the room outside moving through the closet would reduce the temperature by a few degrees, which would be sufficient in this case.
There were already two vents installed in the closet door, so we gathered a few parts we stock and went to work. We first mounted two 12 volt DC fans to the upper vent (we also drilled extra mounting holes for two more fans, in case we need them later). We then used a 12 volt wall mount power supply and a small SPDT miniature toggle switch to power the fans. We mounted the switch and an LCD digital temperature display — for monitoring the exact temperature — inside a PB-1P plastic project box and attached it outside the door.
The DTM0503 temperature display that we used is normally powered by a 1.5 V battery, but we chose to power it with the same DC power supply used for the fans, which required adding a few components to the mix. We used a 1N4741 zener diode soldered in series to the battery terminal on the back of the panel meter to bring the 12 volts down to the 1.5 volts required for the temperature display.
Now that everything is installed, we can see at a glance what the temperature inside the communications closet is and turn the fans off to conserve energy whenever possible.