The fan I've been using cools the projector extremely well, so much that the air coming about is barely warm...it makes a ton of noise though. Anyone know which resistors (and how many) I should use to get the fan down to say half and 3/4 speed (with a switch to select). Google isn't helping much
standard 120mm 115v 20w fan. No idea how much voltage it takes to start
standard 120mm 115v 20w fan. No idea how much voltage it takes to start
Okay, how about this. How would I go about having a power switch for the projector...away from the projector. I don't want to send 115v down the line to the switch and back so I'm looking for other choices. I'm trying to centralize the power controls for everything in the room without having unfiltered power running everywhere. I'm guessing my best bet would be just to use like a pc cable and plug one end into the projector and the other into the control box (with power switches for other devices also installed).
Is there some way I can use a relay that sends a tiny amount of power down the line to activate the projector?
Is there some way I can use a relay that sends a tiny amount of power down the line to activate the projector?
It would be
Much
easier to get a similarly sized DC fan and regulate the speed with the voltage. I suppose you could also get lower-powered AC fans and experiment. Try a muffler or baffle setup to kill some of the noise if you want.
Much
easier to get a similarly sized DC fan and regulate the speed with the voltage. I suppose you could also get lower-powered AC fans and experiment. Try a muffler or baffle setup to kill some of the noise if you want.
Only thing I don't like about that is that its one additional wire going to the projector (I'd just use a 7 or 12v wall adapter)
power adapter provides just enough for the lcd
anyways, I'll just get a quieter fan or go with a DC later. Now I just want to turn the thing on from a different location and get more from the bulb...3/4 of the light is lost, if not more. We still need to find the right reflector for these things
anyways, I'll just get a quieter fan or go with a DC later. Now I just want to turn the thing on from a different location and get more from the bulb...3/4 of the light is lost, if not more. We still need to find the right reflector for these things
You should be able to use a light dimmer, but you might end up with a buzzing sound from the Fan... AC dimmers work by chopping up the AC and reducing the duty cycle of the sine wave. This works good on incandecent lights but with highly inductive loads (fans) it can cause them to buzz.
I just bought a 2 in one fan/light speed controller switch from our local home depot style thrift store for $4. It has two knobs, one for the fan, one for the light, but the only one that works on my AC fans is the switch specificaly made for the fan, not the light.
external fan control box
Hi Guys,
I just built a projector with a closet mounted external box that houses a variac for controlling the speed of three 120VAC 120MM fans and also houses the ballast and cap for a 400W MH lamp. 25 ft. long 16ga. umbilical cables feed the fan voltage and lamp voltage to the projector. Obviously my projector setup is not what one would call compact or portable...
A variac (variable autoformer) is a very nice way to control the fans, as you can dial whatever speed, and hence noise level, that you can get away with temp-wise. The 120V fans typically draw only 200mA, so the Variac can be a small one, even with multiple fans. I used a 2A rated variac for two fans in the projector box and one fan in the external control box itself, to cool the ballast. I haven't measured the voltage I ended up running, but it looks to be about 60V judging by the knob position.
Different fans will behave differently at a given voltage. Some may run freely at 40V and others may need 60V to get spinning. A simpler way to drop the speed of two AC fans that are of the same type is just wire them in series. That worked well for my test runs on the lab bench. I had the fans and variac in my parts stash, so I took the more complex route for the final installation.
This is getting OT, but I also had some good luck mounting the ballast on foam damped springs to cut the transmission of the 60Hz buzz into the cabinet.
Hi Guys,
I just built a projector with a closet mounted external box that houses a variac for controlling the speed of three 120VAC 120MM fans and also houses the ballast and cap for a 400W MH lamp. 25 ft. long 16ga. umbilical cables feed the fan voltage and lamp voltage to the projector. Obviously my projector setup is not what one would call compact or portable...
A variac (variable autoformer) is a very nice way to control the fans, as you can dial whatever speed, and hence noise level, that you can get away with temp-wise. The 120V fans typically draw only 200mA, so the Variac can be a small one, even with multiple fans. I used a 2A rated variac for two fans in the projector box and one fan in the external control box itself, to cool the ballast. I haven't measured the voltage I ended up running, but it looks to be about 60V judging by the knob position.
Different fans will behave differently at a given voltage. Some may run freely at 40V and others may need 60V to get spinning. A simpler way to drop the speed of two AC fans that are of the same type is just wire them in series. That worked well for my test runs on the lab bench. I had the fans and variac in my parts stash, so I took the more complex route for the final installation.
This is getting OT, but I also had some good luck mounting the ballast on foam damped springs to cut the transmission of the 60Hz buzz into the cabinet.
It may not be the most efficient or linear way of doing it but you CAN use resistors to slow an AC fan. My Hafler DH-500 uses two 300 ohm reistors to provide three speeds. If the temp gets too high, a switch closes to short out one resitstor, repeat if it gets warmer still.
My fan is only a 7W one, so you may want to start with something less than 300R. RatShak 10W 100R are cheap enough. Mine will still start with 800R in series, so you have some flexibility.
My fan is only a 7W one, so you may want to start with something less than 300R. RatShak 10W 100R are cheap enough. Mine will still start with 800R in series, so you have some flexibility.
using a resistor is the cheapest opption an otherway would be to use some of the
other inductive methods suggested by other members, you could also use
a lower voltage ac transformer this will also lower the wattage consumption of the fan
cheers
king fanatic of fanatics
only joking!
other inductive methods suggested by other members, you could also use
a lower voltage ac transformer this will also lower the wattage consumption of the fan
cheers
king fanatic of fanatics
only joking!
Are you sure its an AC fan? They usually derive there speed from the freq. not the voltage.
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