# make use of wasted voltage?

I have a 12v battery powering a laser through a 3v Regulator, an LD1117. So the regulator gets pretty hot so I was wondering would it not work if I make use of the voltage the regulator is dissipating as heat by putting a fan and the voltage regulator in a voltage dividing circuit so that the voltage regulator doesn't see the full 12v, maybe if the fan is a 3v fan then the regulator would only see 12-3=9v and thus will create less heat and have a fan to cool it?

1)Will this work?
2)Will my battery life be reduced cause of the fan pulling additional current?

How much current does your laser consume? A simpler solution would be to utilize a switching regulator that runs at much higher efficiency then your linear regulator.

Huh....

Your best option is to reduce the voltage to the regulator..

Maybe pwm could be used to reduce wasted current (a 555 or Arduino etc).

Or simply use a switch mode power supply.

Yes, little switching regulator, dial in 3V output:
300mA http://www.pololu.com/product/2101
600mA http://www.pololu.com/product/2103

1)Will this work?

Yes - but it will not save you anything at all, in fact it will waste a lot more.

2)Will my battery life be reduced cause of the fan pulling additional current?

Forget the fan, even if you ran it on no current the setup would be much less efficient. This is because the potential divider will suck more current than the regulator by itself. All you will succeed in doing is distributing the much higher amount of heat over three devices.

The laser is a 50mW green laser. I do not know how much current it draws. I don't have money to just order parts so I was just trying to make due with what I have

50mW
P=IV, so
0.05 = I * 3V
thus .05/3 = I = 17mA.
Either of the Pololu switchers will provide that.

50mW
P=IV, so
0.05 = I * 3V
thus .05/3 = I = 17mA.
Either of the Pololu switchers will provide that.

Thanx i guess ill have to order stuff then

Grumpy_Mike:

1)Will this work?

Yes - but it will not save you anything at all, in fact it will waste a lot more.

2)Will my battery life be reduced cause of the fan pulling additional current?

Forget the fan, even if you ran it on no current the setup would be much less efficient. This is because the potential divider will suck more current than the regulator by itself. All you will succeed in doing is distributing the much higher amount of heat over three devices.

Reread the posting, the OP suggested putting a fan in series with the regulator - so if
it worked it would not increase dissipation (the fan and the load being the arms of the
divider, not a separate resistive divider).

Of course this doesn't work because the chance of the fan wanting the right amount
of current is negligible, so the regulator will likely see a voltage different to 9V on its
input (the fan will get the wrong voltage, the regulator might well get too little voltage
to work).

Or put another way a fan is neither a voltage or current regulator or a constant
resistance - its a load and needs its own voltage regulator to provide for it.

Thanx that makes sence