Hey everyone!

I would like to split the supply from my 12V DC power supply and make a 6V. I want to be able to have both without using two power supplies to save on room. The power supply that I have should have plenty of amperage. Is there an easy way to reduce the voltage and allow it drive two fans? Thanks for the help!

David

I ordered this, I believe it goes down to 6 volts, should get here this week

http://www.directron.com/f403mini.html

This one is simple and nice too:

http://www.directron.com/fcontroller.html

Here's all they have:

http://www.directron.com/speedcontrol.html

I just want a simple dial, hopefully it will work.

Just add a L7806.

Ebay Linky

Put the 12v on the first leg, ground in the middle, and 6v comes out on the 3rd leg. Up to 1.5a.

can't you just use the +12v and -5v (edit) +5v leads to get 7 volts ? close enough to 6v ?

gs

Just to clarify this to get 7volts you need to use the +12v and the +5v (not -5v).

12v- (+5v) = 7v but 12v - (-5v) = 17v.

Thanks for that... i'll fix my original post...

cheers.
gs

I tested this product yesterday, it does slow the fan but only a tiny bit. It looks like it incorporates the little 3 prong piece suggested in the post below. So I'm back to the old trusties:

http://www.radioshack.com/product/index.js...rentPage=family

I put one 100ohm 10watt plus and extra 10ohm 10watt on the hot line and it slows the fans perfectly. They dont' have a dial or switch, they are just hard wired into the circuit. If you want to slow fans these are simple and they don't overheat. The more fans you put on the circuit, the less resisitor ohm's you need. 110ohm's of resistance runs one fan nice and slow with descent air flow. Not sure if that's your goal.

I suggest following jonjandran's advice. I used a similar trick.

So it's as simple as adding a voltage regulator IC? Well, I can certainly do that. In fact, I think I have an extra one, though I don' t know if it sources enough amps. Have to check on that. Thanks for the info.

the only problem that I have with a resistor slow down is that it's converting the unused power into heat. Though you are using large resistors, so it may not be that big of a deal.

David

The resistors work fine too, they don't get very hot. I'm only running two fans and they are pretty quiet. The adjustable thing I bought was worthless, I went back to the old trusty ceramic resistors.

Those simple linear voltage regulators also put of just as much heat as the resistor method the only difference is that they try hard to provide a constant voltage (hence the regulator part). If you don't need variable speed then a resistor is more then good enough.

Just use a voltage divider circut!

Just use two equal size resistors from +12V to ground in series. Tap off of the center to get +6V!
+12---VVVVV-------VVVVV-----Ground
....................Tap
....................Here!

This won't work as you expect it to. A multimeter hooked up to the center tap will read 6V but as soon as you hook up a load (ie a fan) the voltage will drop. Conceptually you can think of the fan as a resistor being connected in parallel with one of the resistors in the voltage divider. This will obviously change the output voltage. The simplest way is still just a resistor in series with the fan.

OK, so just to fill my idiot question quotient of the day...

You can't just wire two fans together (in parallel) and then wire them to a 12v supply? I've been doing that with one of my projectors for a while now.

If your fans are identical you can connect them in serious. The red lead to +12 V the black lead of the same fan to the red lead of the second one and the black lead of the second one to ground.
They should have the same currant draw and the same speed. You will measure 6V between the two fans and the ground connection.