15 VDC 1000mA to 12VDC 160mA converter

[kerioth]

Hello!

Im new to electronics and this is my first project so bare with me..

i Want to build a fan-controller. i have a power source that is 15VDC 1000mA and the fans require 12VDC 160mA...

How should i do that and does it matter how many fans i want to use?

 

[barry]

The simplest (not necessarily best) solution would be to put an 18 ohm, 1 watt resistor in series with your 15 volt supply. Since your fans draw 160mA, Ohm's law says: (15-12)/0.16=18.75 ohms. I wouldn't do this for electronics, but for fans it shouldn't matter. If you add more fans, you'll have to adjust for the added current.

Or, you could use a voltage regulator, like an LM7812,

 

[Ogu Reginald]

I think and believe that the best option is for you to use 7812 regulator which will regulate the voltage to 12V and can also deliver upto 1000mA, so that when you add more fans: they will all work (provided that the total current requirement of the fans doesn't exceed 1000mA).
Since you are connecting a fan now, you can still go with the 7812 regulator, the fan will just draw a little current from it.

 

[kerioth]

Thanks for the answers! i have a few more..

Do i have to have a regulator for every fan or do i just need one and split up the power after the regulator?

What happens if i put a resistor to every fan? (i dont really know why, but i think that sounded logical when berry mentioned the resistors. and is it still a 18 ohm if thats the case?)

Does the regulator get really hot? do i have to put a heat sink on it or can i have it in a small plastic box?

 

[Ogu Reginald]

You only need a single regulator.
what I advice people is: any IC or any component that has provision for heat sinking is bound to heat up. In your case, I recommend you add a heat sink.
Talking about using a reisitor for each fan: you component count will increase, therby making the cost of your project to increase.

 

[tpetar]

My suggestion is to use LDO regulator for 12V 1-1,5A.

List of appropriate voltage regulators:
https://www.tme.eu/en/katalog/#id_c...10,365&used_params=364:24610;365:24600,24579;

7812 regulator needs 2,5-3V voltage difference between input and output voltages, if you add more fans or other loads voltage can drop and there is chance that 7812 cant do the job in that situation.

Power dissipation is 0,48W (for one fan) on regulator, heatsink is not needed, or you can just fix regulator on PCB copper.



Best regards,
Peter

 

[IanP]

Hello!

Im new to electronics and this is my first project so bare with me..

i Want to build a fan-controller. i have a power source that is 15VDC 1000mA and the fans require 12VDC 160mA...

How should i do that and does it matter how many fans i want to use?

All what you need for the fan is to drop 3V, from 15V to 12V, assuming the 15V source is stable enough. If so, why not to use 4 standard 1N400X diodes connected in series, and as each of diodes drops around 0.7V and can conduct current up to 1A, you will have a voltage drop of 4x0.7V=2.8V and that’s (15-2.8) good enough for a fan ..
:wink:
IanP

 

[rmorris]

All what you need for the fan is to drop 3V, from 15V to 12V, assuming the 15V source is stable enough. If so, why not to use 4 standard 1N400X diodes connected in series, and as each of diodes drops around 0.7V and can conduct current up to 1A, you will have a voltage drop of 4x0.7V=2.8V and that’s (15-2.8) good enough for a fan ..
:wink:
IanP

I'd say go with an LDO 12V regulator as suggested above. Handy if you can use chassis for heatsinking. Need for heatsink depends a lot on degree of non forced cooling eg is the enclosure well ventilated. One fan probably doesn't call for a heatsink.

btw although diodes may be rated at 1A, from past experience they can still get hot enough to melt solder ( well Pb solder anyway ) while still being okay themselves.

 

[kerioth]

Thanks for all the help! you guys are the best!

think ill try a LDO regulator..

Just out of curiosity.. what will happen if i connect the fan to 15v directly? its a standard computer fan...

 

[barry]

It will probably just run 30% faster. And hotter.

 

[Ogu Reginald]

It's life span will be shortened.