I need help creating a circuit board

[junior]

I am currently working on a project and i am not an electrinics expert. My main goal is to figure out the materials, and maybe some basic guidance on putting a control board together. The circuit needs to regulate Power Draw (@ +12V): 0.13A. Plus a ON and OFF switch(which i want to be able to switch speeds). Ideally I want the power source to be a 9V battery. And i would like to maintain this as lightweight as possible. if anyone has any suggestions i would greatly appreciate it.

P.S also if you could give me an estimate on power draw and the approximate time the battery would last. thank you and sorry about misspelling.

 

[davenn]

hi junior
welcome to the forums

well you can take 9V from a battery and boost it to 12V using a boost DC-DC converter.

What do you want to switch speeds of ? you havent said
we cant give you any power usage figured unless you tell us what the load on the power supply if going to be .... what are you supplying power to? and what is it voltage and current requirements ?
I will guess that could be 12V @ 130mA in which case your power supply needs to be able to handle more than that.
up converting from a 9V battery to 12V isnt really going to work well as those small 9V batteries dont have a lot of current capability anyway ... its only going to last a VERY SHORT time

Why cant you do the obvious and use a 12V battery ? size ?

Dave

 

[junior]

It is going to be used on a cooling fan for a computer. but i will not use it on a computer. I dont need a long time it would be atleast 30 minutes. regarding the battery, i need the cooling system to be portable and as light as possible and i dont know if there is a battery that has more power and is as light or less. Power Draw (@ +12V): 0.13A - this is the power requirement that i got from the specs. hope this is enough info.

 

[CocaCola]

If it's a 12V computer fan just run it off the 9V battery directly, really no need to waste in the up conversion to 12V you should get that 30 minutes out of it, with only a slight decrease in fan output... Getting speed control 'properly' is a little more work, you can attempt to do it with diodes or resistors but they both have negative consequences over doing it properly with pulse width modulation...

 

[junior]

Is there any thing that i could do to maintain the fan output and get the amount of time that i desire? also how would i be able to control the speed? and im not sure but i think that there are different types of diodes right? if so which one should i use?

 

[CocaCola]

Get a battery holder like this, complete with your on/off switch...

http://www.ebay.com/itm/Hold-8-AA-S...045?pt=LH_DefaultDomain_0&hash=item27cb3bea7d

The AA batteries will provide a substantial increase in run time over a 9V, and you are now at a nominal 12V... There are also similar AAA holders...

As for speed control, your generic diodes like 1N4001 put in series will drop about .7 Volts each, thus the more you put in series the slower the fan will spin, but it also loses torque, same with using a series potentiometer or resistors, you lose toque and this can cause undesirable consequences, and it's wasteful...

The best way is with PWM similar to what this guy did...
http://pcbheaven.com/circuitpages/PWM_Fan_controller_using_a_555/

Have you tried the fan with just the 9V?

 

[junior]

Thank you very much to both of you,
I work with fully encapsulated suits that fog up, it is extremely difficult to see because of the fog that formulates inside the suit. thebattery holder looks like a good option. i am currently in training but once i got back to alaska i will test the fan and batteries to see which one would fit me best. Again Thank you both.