hi

as title says im working on little project and i wana connect my 12v pc fan on 9v battery. is there any transformator i can get or something else?
i know only basics that i learned in school about electronics and nothing else so pls dont use words i wotn understand

 

No need for anything. Just hook it up to the 9V battery.. The fan will just spin slower due to the decreased voltage.

 

No need for anything. Just hook it up to the 9V battery.. The fan will just spin slower due to the decreased voltage.

i know that but i need to get full power from fan

 

You could make a 9V to 12V boost converter...but...you can't get much power out of a 9V PP3 battery, and you will get even less, due to <100% efficiency, with a boost converter. There's no free lunch.

Ken

 

It would be much better and cheaper to get a fan rated for the power source you have rather than going to the expense of converting your odd power source to the needs of a fan that you happen to have on hand. A new fan is dirt cheap compared to a DC-DC converter (most of which are also for standard input voltages like 5, 12, 24, or 48 volts).

However, you are unlikely to find a fan rated for 9 volts. What is your 9 volt power source? Hopefully not a 9 volt "transistor" battery which doesn't have the energy content to run a fan for long. Why don't you fill us in on just what you are trying to accomplish? What is the current draw of your fan and the energy content/current rating of your power source?

If you just want to construct a project for fun, there are many DC-DC controllers with copious application information available from the semiconductor manufacturers. Maxim comes to mind but others offer similar devices. Do a parametric search at the semiconductor mfgr. sites and study the various devices offered.

If your 9 volt source is not energy limited and efficiency is not an issue, your best bet might be to obtain a 5 volt fan (very common) and use a linear regulator like a 7805 to power the fan. Cheap as dirt, but only about 50% efficiency with half the energy thrown away heating the regulator (which may need a heat sink, depending upon the size of your fan).

You could use the same strategy with much better efficiency using a "Simple Switcher" bucking regulator to drive the 5 volt fan. The "Simple Switcher" is about the simplest high efficiency switch mode device to apply. Google "simple switcher," go to the National site and fill in the voltage/current data and they provide a complete circuit.

If cost is no object, go to supplier's sites like DigiKey or Mouser and search their DC-DC converters. (But this seems like a really silly way to go.)

awright

 

Is there any reason you can't use a 12v power source?

 

It would be much better and cheaper to get a fan rated for the power source you have rather than going to the expense of converting your odd power source to the needs of a fan that you happen to have on hand. A new fan is dirt cheap compared to a DC-DC converter (most of which are also for standard input voltages like 5, 12, 24, or 48 volts).

However, you are unlikely to find a fan rated for 9 volts. What is your 9 volt power source? Hopefully not a 9 volt "transistor" battery which doesn't have the energy content to run a fan for long. Why don't you fill us in on just what you are trying to accomplish? What is the current draw of your fan and the energy content/current rating of your power source?

If you just want to construct a project for fun, there are many DC-DC controllers with copious application information available from the semiconductor manufacturers. Maxim comes to mind but others offer similar devices. Do a parametric search at the semiconductor mfgr. sites and study the various devices offered.

If your 9 volt source is not energy limited and efficiency is not an issue, your best bet might be to obtain a 5 volt fan (very common) and use a linear regulator like a 7805 to power the fan. Cheap as dirt, but only about 50% efficiency with half the energy thrown away heating the regulator (which may need a heat sink, depending upon the size of your fan).

You could use the same strategy with much better efficiency using a "Simple Switcher" bucking regulator to drive the 5 volt fan. The "Simple Switcher" is about the simplest high efficiency switch mode device to apply. Google "simple switcher," go to the National site and fill in the voltage/current data and they provide a complete circuit.

If cost is no object, go to supplier's sites like DigiKey or Mouser and search their DC-DC converters. (But this seems like a really silly way to go.)

awright

tnx i searched thees converters and they are way to expensive..i like idea with 5v fan but can you pls explane this linear regulator thing i have some links from my local hardware store, they are on my lenguage but you should understand:
http://www.chipoteka.hr/www_new/modules/moduli/shop/product.php?sifra=0351780501
http://www.chipoteka.hr/www_new/modules/moduli/shop/product.php?sifra=0350780501
http://www.chipoteka.hr/www_new/modules/moduli/shop/product.php?sifra=0350780502
thees 3 are regulators i found on their site and if you could pls just tell me is that what i need?

and also i there is any link on how to use thees

 

Is there any reason you can't use a 12v power source?

i cant use 12v source cause im making small hovercraft and i need small bateries

 

Your making a hovercraft with a 12V PC fan and a 9V Battery. I wish you luck!
I was going to suggest you place 2 9V batteries in series and use a trimpot to scale the voltage down, but that will add more weight. Try 3 LiPo 4.2V Batteries.

 

Remember to throttle your lift via intake retarding, not by changing fan speed.

 

I don't think a PC fan is going to be strong enough to lift itself, the power source and the structural part.

A 12V lithium photo battery might have a better shot at it.