jocanon
Member
I am building a hush box for my home movie projector in which the projector will be fully encased within an acoustically treated box. The only openings will be one for ventilation intake and a second for ventilation exhaust with an 4" duct and an inline duct fan connected after the hush box. The fan will pull air from the theater room into the intake vent of the hush box and out the exhaust vent to finally be expelled outside the theater room in the upstairs loft which is an open area that opens up to basically the rest of the house (except rooms that have doors to close them off). The box will have a protrusion into the box that butts right up next to the lens with soundproofing and insulated materiel smashed between the physical case of the projector and the wooden box so as to allow the projected image to escape the hush box without the need of passing through a second layer of glass.
As you can imagine, without good airflow through the hush box, it will get quite hot inside and destroy the projector. I have a DLP projector and the fan constantly blows warm to hot air, it's basically a little heater. (A side benefit of the hush box is that I will be able to vent the hot air into the greater area of the house and out of the theater room so it doesn't heat up in the theater room while watching movies). So my objective is to come up with the best, easiest, smartest, most cost effective way to ensure the fan is always running and to notify me if it is not so I can turn off the projector.
I do not want the warning indicator to automatically cut power to the projector. I think this would be a bad idea because the cooling vent of the projector has to run for a minute or so after the projector is powered off in order to cool the bulb. If there was a false warning or even if it was a valid warning, I would not want it to just cut power off to the projector without allowing it to run the fan for that minute or so to cool the bulb. So I just want something that tells me the fan is malfunctioning, then I will manually turn off the projector myself. I do not need the inline duct fan warning system to communicate with the projector in any way.
I should also mention, another goal is that no noise leaks into the theater room, hence the projector hush box. Also, in order for no noise, I am mounting a very quiet inline duct fan up in the attic using acoustically rated ducting so the fan will not be heard in the theater room at all. I am also using oversized return vent grills for the intake in the hopes I will not even hear the air flowing into it. If I succeed at my objective, the theater room will be completely silent, until you start the movie of courses, then it will be very loud
So in light of the fact that cooling is critical and that there will be no audible or visual indication that the fan is on or working, I think it would be smart to figure out some way to indicate fan failure that will be impossible to not notice while in the theater room. Which means it might need a light and a buzzer - the buzzer may not be audible over the sound of the movie, so a light would be in order, better yet, both.
My ideas so far are some sort of warning light or warning buzzer (as mentioned above), but I do not know how I would do that. I even thought about putting some confetti or something hanging down from the intake vent that will suck up to the vent when airflow is present and simply hang down when it is not. The confetti idea might be the easiest way, but I would rather have a warning buzzer or light go off because the vent will be in the back of the room and while watching a movie I do not want to be looking back at the vent every 5 min to be sure it is still getting cool air. Maybe there is a way to incorporate both these ideas, that is, something to sense airflow and then a buzzer or warning light or both that go off if there is none preset. However, it would be slightly more complex because I would only want this warning to activate when the projector is on and blowing hot air into the box because the fan is on a thermal switch to where it only comes on when it senses the heat blowing out of the projector. Maybe what ever warning circuit I put in there simply needs to be hooked up to this same thermal switch the duct fan is on. Also, I would probably want a 5 second delay or so as to avoid the warning going off momentarily every time I power up the projector before the fan has a second to kick in and create airflow through the 25 feet of duct work.
I know just enough about electronics and have some experience soldering small components to be dangerous, but I do not know enough to design my own circuits, I can follow a schematic. I am hoping there are experts on this forum that can help me first of all come up with a good plan/schematic, then second of all tell me what components I would need and how to connect them all up. I am thinking this will probably be a fairly simple setup for somebody a little more electronically inclined than I.
As a side note, I believe the projector has built in thermal shutdown if it gets too hot, but I do not want to rely solely on that as I would not want to push the projector all the way to that point before powering down.
As you can imagine, without good airflow through the hush box, it will get quite hot inside and destroy the projector. I have a DLP projector and the fan constantly blows warm to hot air, it's basically a little heater. (A side benefit of the hush box is that I will be able to vent the hot air into the greater area of the house and out of the theater room so it doesn't heat up in the theater room while watching movies). So my objective is to come up with the best, easiest, smartest, most cost effective way to ensure the fan is always running and to notify me if it is not so I can turn off the projector.
I do not want the warning indicator to automatically cut power to the projector. I think this would be a bad idea because the cooling vent of the projector has to run for a minute or so after the projector is powered off in order to cool the bulb. If there was a false warning or even if it was a valid warning, I would not want it to just cut power off to the projector without allowing it to run the fan for that minute or so to cool the bulb. So I just want something that tells me the fan is malfunctioning, then I will manually turn off the projector myself. I do not need the inline duct fan warning system to communicate with the projector in any way.
I should also mention, another goal is that no noise leaks into the theater room, hence the projector hush box. Also, in order for no noise, I am mounting a very quiet inline duct fan up in the attic using acoustically rated ducting so the fan will not be heard in the theater room at all. I am also using oversized return vent grills for the intake in the hopes I will not even hear the air flowing into it. If I succeed at my objective, the theater room will be completely silent, until you start the movie of courses, then it will be very loud
So in light of the fact that cooling is critical and that there will be no audible or visual indication that the fan is on or working, I think it would be smart to figure out some way to indicate fan failure that will be impossible to not notice while in the theater room. Which means it might need a light and a buzzer - the buzzer may not be audible over the sound of the movie, so a light would be in order, better yet, both.My ideas so far are some sort of warning light or warning buzzer (as mentioned above), but I do not know how I would do that. I even thought about putting some confetti or something hanging down from the intake vent that will suck up to the vent when airflow is present and simply hang down when it is not. The confetti idea might be the easiest way, but I would rather have a warning buzzer or light go off because the vent will be in the back of the room and while watching a movie I do not want to be looking back at the vent every 5 min to be sure it is still getting cool air. Maybe there is a way to incorporate both these ideas, that is, something to sense airflow and then a buzzer or warning light or both that go off if there is none preset. However, it would be slightly more complex because I would only want this warning to activate when the projector is on and blowing hot air into the box because the fan is on a thermal switch to where it only comes on when it senses the heat blowing out of the projector. Maybe what ever warning circuit I put in there simply needs to be hooked up to this same thermal switch the duct fan is on. Also, I would probably want a 5 second delay or so as to avoid the warning going off momentarily every time I power up the projector before the fan has a second to kick in and create airflow through the 25 feet of duct work.
I know just enough about electronics and have some experience soldering small components to be dangerous, but I do not know enough to design my own circuits, I can follow a schematic. I am hoping there are experts on this forum that can help me first of all come up with a good plan/schematic, then second of all tell me what components I would need and how to connect them all up. I am thinking this will probably be a fairly simple setup for somebody a little more electronically inclined than I.
As a side note, I believe the projector has built in thermal shutdown if it gets too hot, but I do not want to rely solely on that as I would not want to push the projector all the way to that point before powering down.
