I have an amp that has an internal fan. At 60*C, the fan turns on and gets 7V. At 80*C, the fan gets the full voltage of the car.
What I'm trying to do:
I have 4 computer case fans and I'm trying to get them to come on as the amps get hotter. Instead of doing a thermistor circuit, I want to try something a little easier.
I want the fans to come on slowly at a lower voltage, like the 7V that the internal fan does, but how would I accomplish that? I will be tying on to the existing fan, so I can get full voltage to the fans when the amp hits 80*, but is there a way I can have them turn on to around 7V when the internal fan hits 7V. I cant think of anything off hand, so heres one of my ideas:
Is there an inexpensive way to knock down 12V to around 5? I would hook this up to an ignition wire so the fan will turn on when the amps do and take that wire and knock it down to 5V.
If anyone else has any other suggestions, Im certainly open to them!
-Cody
They make voltage regulators that would work perfect. You can pick one up at Radioshack for a few bucks - part number 7805. The 7805s they carry are good for 1A, but over 100mA you should add a heat sink. I'm not sure what kind of current your fans will pull at 5vdc but that is something you will need to know. You can add multiple 7805s to increase current cappacity.
You could also use a couple transistors and amplify the amp's fan signal. Depending on the total current load of the fans this may be a better solution. You would basically need one NPN transistor and one PNP transistor.
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Kevin Pierson
First what voltage are the fans rated at?
Most computer fans are 12v.
How much current draw for each one?
How many fans from the supply voltage?
This is important so a circuit can be designed for your application.
A simple Low-Tech way, would be to find a 5v phone charger for each fan that converts 12v to 5v. Disassemble it and solder the wires where you need them.
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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !
best buy sales a piece that would work its called HITCHIKER it sales for $20 bucks hook one end to 12volts the other end to your fans and u can controll the voltage by turning a dial on the unit ...
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MY FRIENDS CALL ME BUTCHER I FEAR NO WIRES THAT DONT BELONG.......................