I got a stupid question here...

[BlazeMaster]

I'm trying to build a hush box for my projector. Found 2 120mm fans and a power supply. I plugged the power supply into the wall and plugged in the fans, but there seems to be no power coming from the power supply. Do I need another separate switch, even though the back of the power supply has a switch? If so, what kind of switch should I be looking for? This power supply will only be used to power 2-4 120mm fans. Thanks for helping.

[Marzen]

If it's a computer power supply, it may normally be switched on from the momentary switch on the front of the cpu case - which usually pulls that signal line low to enable the power supply. You could use another power supply for the fans, a simple little ac to dc type; either wall mount or inline. The latter would have a smaller footprint and wouldn't require the additional fan built into a computer power supply.
I would think someone must have already built a simple remote-on circuit that's enabled from the projector's trigger out jack. Google turns up one here that will handle 0-5vdc input trigger and switch up to a 16A load @ 120vac for $26. http://www.makingthings.com/products..._ac_switch.htm


Ward

[BlazeMaster]

I just need a simple switch for the power supply. Can I find these switches at local electronic stores?

[Marzen]

Yeah sure. But how do you turn it off? I suppose you could use the kill switch on the back of the pwr supply. Holding the momentary switch in for 5 seconds may shut it down but leave it in a low power state where the 5v output is still live. Radio shack would have the momentary switch.

[Lex]

put it in a cheapo computer case, and use that switch, or just remove the switch to use. I would think it's just contacting 2 contact points, not a big deal, but as Ward said, the computer power supply will be expecting you to hold down the button to shut it down, unless you power the OS down, which you will not have. Or just yank the power cord out of the wall, that will turn it off, lol.

[Kevin P]

I would get a 12V 1 amp wall wart to power the fans. First of all, it's more compact and quieter than a PC PSU. Second, you don't have to worry about the button to turn the fans on/off. Third, most PC PSUs require a load on them in order to work properly. By a load, I mean more than just a couple fans. They need to have a few amps' load on them (typical PC, hard drive etc.) in order to regulate the voltage properly.

A wall wart is a lot easier. You can easily wire a switch in to turn the fans off.

[Marzen]

It strikes me as a little odd that I couldn't find a site where someone already did this and posted the details. Since this is WAY more interesting than work, I think I'll look into this tomorrow. Besisides, I'd like to get an intro level projector myself. I would think a thermostat controlled ac switch for fans would continue to move air after the pj was shut down. Add a piezo buzzer for over temp alarm in case of fan failure and a little led or lcd readout for the box temp would be a plus. I'd like to think that would come in under $50. Kevin, don't the pc mod guys have a remote panel lcd readout with a wired sensor?

[BlazeMaster]

Where can I find the wall wart? And if I do, does the wall wart has the connectors that the PC fans use?

[Marzen]

Radio shack & Jameco are 2 places off the top of my head; and no they won't have a compatible mating jack for the fans. You'll need to snip off the fan connector & solder or use wire nuts. Check the polarity of the fan leads after they're connected to power so they all blow in the same direction. How far apart are the fans when installed? Are the fan leads long enough to reach to one central location for power?

Regards,
Ward

[BlazeMaster]

thanks for your help so far Marzen. This sounds like a lot of work for someone that is not good with electric lines. So I can find the wall wart at Radio Shack? And the Wall wart should be able to power the fans just as long they use the same connectors? I'm thinking about having 2 fans for the hushbox. One on right and one on left side of the projector, to help intake and exhausting the air flow in the box. Anybody have any design suggestions for the box?

[PewterTA]

Blazemaster, is the electrical outlet switched? If so, you can just jump two of the pins on the plug that would plug into the motherboard and it will stay on all the time. Then just switch the fans off and on with the projector... If you need to create a 12volt trigger, I can help you out with that as well.

[Marzen]

I couldn't find a wall wart pwr supply on RadioShack.com, unbelievable! I think they have them? Anyway, here's the same thing only from Jameco 120VAC to 12VDC 1 amp regulated pwr supply

[Kevin P]

Marzen & Blazemaster, look here. I knew RadioShack had them, because I bought one recently (the 500 mA model).

[BlazeMaster]

I did a lil bit of research and asked around a bit. And it seems that I've been told to do what PewterTA had suggested, to just get a power cord to short the 4th and 5th pin on the plug that connect to the motherboard. Supposedly that would enable the PSU to be turned on by the switch that it came with. Now I just gotta find my a single power cable to connect to the 4th and 5th pin.
Now, this creates another problem. Where am I going to put the PSU? Initially, I was thinking about putting it inside the box so the fan noise from the PSU would be contained inside, but this makes turning it on and off more of a hassle. A 12v trigger might be the best way to go, this is much more complicated than I thought it would be.

[Marzen]

... this is much more complicated than I thought it would be.

Ain't it always
Is your room already finished? I ask because my basement is currently unfinished so I have access to run wiring where needed.
Can you reach the installed hush box while standing? If you were to install a dc switch for the fans on the box's exterior.
Where's the ac outlet for the pj, inside the box or out?
Where is the pj fan intake and exhaust located?

Ward

[BlazeMaster]

I finally got the PSU to work now. My room is a HT/bedroom, I wish I have a dedicated room for this. I'll probably end up putting the PSU somewhere else, because the PSU is audible, but the fans are silent. Now my next dilema is to find a cable long enough to send the power from the PSU to the two fans. The reason I'm keeping the PSU away from the projector now is:
1. it is audible.
2. it will add unwanted weight to the hush box.
3. it will generate more unwanted heat after it's been on for a while.

The AC outlet is outside of the box.
To be honest with you I can't tell which side of the projector is intake/exhaust. One side feels warm while the other side feels cool. I can feel a little bit of airflow on both side of the projector.

[Marzen]

>cool side in, warm side exit.
3 more questions to get some ideas on your options:
1) Will the pj be mounted up near the ceiling?
2) Where is the nearest wall outlet (ie - relatively below the mounting location or way off to the side, and probably standard outlet height from the floor ~ 1ft)
3) Is the area used as a bedroom, or do you have some leeway?

[BlazeMaster]

oh ok, cool side in, warm side exit.
1. yes, the pj will be near the ceiling, about a foot below the ceiling. Acutally near where the ceiling and the back wall meet.
2. the nearest wall outlet is about a foot off the ground and not near the pj at all. That's why I was thinking about having the PSU closer to the outlet, and run some cables to the fans in the hush box. It will keep the heat of the PSU out of the box as well and make the box's overall weight much lighter and easier to mount.
3. the room is used as a bedroom, but I do have some leeway. The front of the room, is nearly completly filled with acoustic treatment. What kind of leeway did you have in mind?

[Marzen]

What kind of leeway did you have in mind?

Oh, just cutting some holes in the wall for a new outlet and a switch to control it :demon: , or look at cable raceways that attach to the wall for hiding an extension cord up to the pj ala http://www.monosystems.com/pdf/msibg05.pdf
I haven't looked much at hush box designs as I didn't get my pj until yesterday. I'm going up to Lowe's here shortly to look for M4 mounting screws and some hardware for a temporary mounting. Do you have access to power tools for making a wooden box?

Ward