Hoot help out pls , alot of help!!

[jbslow]

Hoot I have a few questions on the LM338K setup try to be patient to say the least I am electronically illiterate.

Ok I need some help in the resistor capacitor area.

R1 - Ok the pic says 120(ohms right), if thats right then how many watts should I need (1/8 , 1/4 ,1/2 , 1 or more) keep in mind I'm using the exact same fan as you wrote about.

R2 - Ok you already wrote I'll only need 1-2K ohms , its a multi turn potentiometer.

C1 - Ok the pic you included quotes 0.1 uF , ok I found one with .1uF its a Polyester Capacitor 100v±10%.Please tell me if this will work , if not what should I buy?

C2 - Well this one is listed as 1 uF now I didnt see on of these but I did see mF and pF this one I'll need some help on it totality.

Board - what do I need like a PC200 or a Pc403 or something???

Heat sink - Can I use like a ram hs from radio shack or should I get something bigger . please give me a recommendation.

Dang thats sure is alot of questions sorry about that I really hope you can take the time to help me out here , I will really appriciate feedback.

[LimeyGreg]

Power through the resistor network is V x V/R. For 12v and 5K-ohm approx 29mW, for 24v it's 115mW so a 1/4W will be fine.

C1 is fine, C2 is a 1uF (microFarad) electrolytic (or possibly Tantalum Bead). Be sure you get the polarity correct when you connect it or it'll go "bang".

Not sure about the board but I assume it was built on a standard 0.1" pitch breadboard.

The heatsink is a standard type for the case and the place that sold you the voltage reg should have one. It's just a small heatsink with a hole through it.

[jbslow]

Thanks a million LimeyGreg!!!

edit:
Hey LimeyGreg the fan is 12v , 5.1a with 62w just in case any of those values change because of these specs.

[LimeyGreg]

Hmm, big fan - don't get too close to the intake, you might get sucked in. :eek:

No, it doesn't change the values as that current will be passing through the regulator - hence the need for the heatsink.

[jbslow]

Ha thats for sure I'm always a little worrier about my feet getting sucked into the squirl cage , ouch.

LimeyGreg I was chating with this guy from a DC electronics store here in town and he seemed to think even with the LM338K I should still setup a alternetive power supply fo this fan. DO you think a 350W sparkle will be able to handle those watts even with the regulators atached? I already know without a regulator it will damage a 300W Sparkle rigged at 7v via the molex mod. My 5V rail used to run at 4.93-4.78 but now it wont support the fan and without the fan it runs at 4.79-4.64 so I surly need a replacment.

[jbslow]

Well I just got another pole blower but this one is AC 115v 60/50hz .65a(printed on fan)-.74a(printed on motor) and 134 cfm , perfect. Of cource now I need to figure out what the green (3rd line) is used for.

1white - 115v , 60/50hz
1black - should be ground (maybe 60/50hz)
1green - I dont know maybe I need a 3 pin wall plug??

[LimeyGreg]

You need to check the specs of the psu, specifically the line you are using to power the fan. If you are using that supply to power both your comp and the fan then your psu may be overloaded.

I'm not sure which mod you mean but assume you are talking about the +5v and +12v to give you +7v. Your 5v line usually has a higher current rating than the 12v but in the mod the current is coming from the 12v rail and passing through your 5v rail to complete the cct and it may be the 12v that was limiting you. I would go to a 400w possibly a 450w.

Now I am assuming you are using the 12v rail with the regulator being used to control the voltage and hence the speed. You need to add up the currents on the 12v rail to be sure it isn't being asked to do too much, even though you have a regulator you are still pulling quite a bit of current it's just that the voltage to the fan is now controlled but the price is a hot regulator.

If you are thinking of adding a peltier or more fans I would look at getting a 13.8v supply, or better still an adjustable supply.

The green wire is the ground of the motor assembly and should be preferably be connected to the ground of ac cord you are using to supply the fan, white is "hot" and black is "neutral" - not ground. If you want to control it's speed you may want to look at a "fan speed controller" that can be used to control say a ceiling fan.

[jbslow]

Nice thank you , I'll need to pic up another plug for the AC fan after work (I was first planning on just using a plug from a extenision cord but this one only has 2 wires and two plugs).

[jbslow]

Ok its all up and running again got the 3 prong plug and a inline on/off switch rigger about 7 in from the power switch so hopfully nobody in the house will forget to turn on the fan :eek: . Its ok if someone forgetts because I git a kill switch activated @60°C (which I know works by the way because when the first fan stopped running) , thank you epox.

This one runs at 134cfm which is pretty close to the 7v setup I had going with the 176cfm fan , finally all stable and cool again of cource I still need to buy the new psu.

Thank you LemeyGreg maybe another time I'll try the DC fan with the LM338K but now there is more important things to worry about.