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Author Topic: getting more watts  (Read 3009 times)

archades

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getting more watts
« Reply #10 on: December 30, 2003, 02:50:37 PM »

whats a pwm?
im somwhow either planning to just use the 12 volt 13 watt to tell a circuit what voltage to select and get power form molex, or to some way add the 13 watts to the molex power and still be able to limit the speeds someway
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viridius

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getting more watts
« Reply #11 on: December 30, 2003, 03:00:48 PM »

The Aerogate uses a LM317 voltage regulator to change the voltage that goes to the fan.  The weakness of the LM317 is the limited current handling capability (about one amp).  Your fans will require about one amp each, so you will need to use a system capable of giving higher current.  While you could use a straight-up rheostat, it would cost you $50 and be over three inches wide.  You could also use a higher-current variant of the LM317 such as the PQ7DV10 that costs $7, but you would have to put a giant heatsink on it to dissipate the heat.  PWM (pulse width modulation) works by turning your fans on and off fast enough to give the impression of a lower voltage.  By changing the amount of time the fans are on relative to the time the fans are off, you can change the speed at which they rotate.  This requires an inexpensive transistor and a cheap pulse generator.  The heatsink for the transistor, since it only dissipates heat during turn-on and turn-off, is much smaller than the transistor for the voltage regulator, which dissipates heat all the time.
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archades

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getting more watts
« Reply #12 on: December 30, 2003, 03:15:24 PM »

ahh nice, but will it gather the power from a molex yet be controlled by the aerogate?

would the pwm supply enough current if changed with the current voltage controller?
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archades

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« Reply #13 on: April 20, 2004, 06:26:23 PM »

bump

still havent made this yet
maybe just a simple amplifying circuit will do
maybe have a current resisting setup, somehow, that  can block off soem current from teh molex power source, so the fans dont get too much current in case i add or take off a fan

the amplifier should add the current just like in car stereo's etc, as long as i can get 0 and 100 % fan speeds with little heat and still use that single aerogate channel

i know im difficult
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viridius

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getting more watts
« Reply #14 on: April 20, 2004, 09:11:49 PM »

I don't think fan control works like car stereos, but you'd have to give me more information about what exactly you want again.
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linear

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« Reply #15 on: April 20, 2004, 11:49:00 PM »

How about this: build several simple unity gain emitter-follower circuits to track the voltage of the fan controller? Transistors are cheap, TIP31A for about 69 cents a whack ought to do the numbers.
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archades

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« Reply #16 on: April 21, 2004, 01:31:18 PM »

basically the fan controller cant provide enough current for the fans i want, so i wanted to build a circuit to get the power from the 12 volt molex inside the pc

my thoughts so far, would be a fan controller to a pwm that is controlled by the voltage, that speeds up or slows by the voltage, then that goes to the transistor

so the molex power supply goes through a transistor acting like a gate, so that when the voltage is low on the fan controller the pwm only turns on and off for 20% time, therefore the gates open and let the molex powersource is let throuygh at 20%, if u can understand, and if it was at 100% the gate would be kept open letting all teh current through

so the fans are powered by the transistor through the molex power supply, not being fed by the fan controlled/rheobus

for any of the other suggestions, anyone know how to wire em up:P
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linear

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« Reply #17 on: April 21, 2004, 03:17:34 PM »

Here's ye olde emitter follower diagrammed nicely and explained for ya:
http://www.cpemma.co.uk/ef.html.

In your case the voltage divider shown is the existing fanbus, so it's even simpler.
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archades

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« Reply #18 on: April 21, 2004, 04:17:14 PM »

no no no :P

this isnt what im looking for
this u need to turn soemthing yourself

i want to use a power supply SEPERATE from the fan controller, or else the fan controller will just fry itself

so far from what i see, is that teh fan controlled can power a pwm circuit, but i dunno how to make the circuit however, i need the voltage to have 12 volts, 100% pwm, 0 volts, 0%, 6 volts 50% so forth and so on

the varying speed will goto the transistor and turn it on and off letting through the power source 2, dropping the speed or raising it

understand now? :D
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archades

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« Reply #19 on: April 21, 2004, 09:28:48 PM »

just ran some numbers

the fans are Vantec Tornado 80mm

power supply will be most likely Antec TruePower 550watt

the fans are 9.1watt @12volt each, so 6 of these beauties will be a nice 54.6watts, drawing 4.55amp through the line

so i need to find a transistor that could handle that current, and maybe some diodes to protect the psu?

still looking for a decent pwm circuit to drive the transistor

and i dunno what to do with 13 watts i wont be using either:P[/url]
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