Tempature Controlled 12 volt DC fan

[Ryan Ashline]

I have a video projector mounted in a sealed box which has an intake
with a fan pushing air in and an exhaust which has a second fan
blowing air out. The system keeps the projector supplied with enough
air to keep it cool but even with the fans mounted in the attack 10
feet away I can still hear them. What I would like to find or build
is something that will turn on the exhuast fan when tempatures reach a
certain level inside the box. When or if the tempature reaches a
second elevated level I would then like to kick on the intake fan to
increse the overall CFM the projector box is given. Currently I have
a wall switch that turns on a 3 amp dc power supply that feeds both
fans at the same time. One thought i had was to use two inexpensive
home hvac thermostates mounted inside the projector box to trigger
each fan seperatly based on the tempature set on each one. However i
am not sure if these are ac or dc and what i would need to get them to
control the fans. Another question I had was if switching the fans on
and off with lower the life of the fans?

Thanks for any help or direction anyone can give!

Ryan

 

[R.Legg]

ashline@yahoo.com (Ryan Ashline) wrote in message news:<54109d7d.0405091748.27b4481e@posting.google.com>...

I have a video projector mounted in a sealed box which has an intake
with a fan pushing air in and an exhaust which has a second fan
blowing air out. The system keeps the projector supplied with enough
air to keep it cool but even with the fans mounted in the attack 10
feet away I can still hear them. What I would like to find or build
is something that will turn on the exhuast fan when tempatures reach a
certain level inside the box. When or if the tempature reaches a
second elevated level I would then like to kick on the intake fan to
increse the overall CFM the projector box is given. Currently I have
a wall switch that turns on a 3 amp dc power supply that feeds both
fans at the same time. One thought i had was to use two inexpensive
home hvac thermostates mounted inside the projector box to trigger
each fan seperatly based on the tempature set on each one. However i
am not sure if these are ac or dc and what i would need to get them to
control the fans. Another question I had was if switching the fans on
and off with lower the life of the fans?

The air movement is intended to cool one thing - the lamp. The fact

that two fans are used shows that this is a critical requirement for
lamp life, or the expense wouls not have been undertaken in the
products development. At the same time, it is unlikely that the
product was indended to produce unacceptible noise levels.

As fans age they get more noisy. Replace the fans with the recommended
new part. If you complain about the noise to the manufacturer, they
may have some modifications or upgrades to suggest. These may simply
involve increasing the distance between the impeller and any physical
mounting hardware or grillwork - typically the biggest noise maker in
a properly working fan assembly. Even a tenth of an inch can produce
signifigant reductions.

RL

 

[N. Thornton]

ashline@yahoo.com (Ryan Ashline) wrote in message news:<54109d7d.0405091748.27b4481e@posting.google.com>...

I have a video projector mounted in a sealed box which has an intake
with a fan pushing air in and an exhaust which has a second fan
blowing air out. The system keeps the projector supplied with enough
air to keep it cool but even with the fans mounted in the attack 10
feet away I can still hear them. What I would like to find or build
is something that will turn on the exhuast fan when tempatures reach a
certain level inside the box. When or if the tempature reaches a
second elevated level I would then like to kick on the intake fan to
increse the overall CFM the projector box is given. Currently I have
a wall switch that turns on a 3 amp dc power supply that feeds both
fans at the same time. One thought i had was to use two inexpensive
home hvac thermostates mounted inside the projector box to trigger
each fan seperatly based on the tempature set on each one. However i
am not sure if these are ac or dc and what i would need to get them to
control the fans. Another question I had was if switching the fans on
and off with lower the life of the fans?

Switching should not reduce fan life - assuming you dont switch them
once every second.

A simple way to reduce noise is to add a wood box over the in and
outlets with a fan sized hole in it in in one side, such a place that
the noise has to turn through 90 deg to escape. Carpet line the boxes
and you will find significant improvement.

Whatever type fo thermostat you use for fan control needs to have
reasonably quick temp chanmge response: something that took 20 minutes
to respond would be no good.

I would also consider a mode where teh 2 fans run in series: this
would give huge quietening while still providing at least some
airflow. This would generally reduce the amount of time the fans would
need to spend on full speed.

Larger lower speed fans normally have much lower noise output.

BTW I think R Legg may have misunderstood your situation.


Regards, NT