LM317 Help

Depends what you declare "ground" to be.

AWOL: Depends what you declare "ground" to be.

Correct, we would need to know if he is using the PC supply for any other loads, or desires to.

Lefty

I'll be using the same PSU for: Pumps (Water Cooling), Micro Controllers, Fans

Mike has the best solution; use a single power FET and control it with a PWM output from Arduino. And it (could) handle a lot more current than an LM317T.

Nothing against the LM317T. I once bought a barrel of 14,000 of them for $55 from a junkyard near IBM :slight_smile: I’ll send 5 to anyone who’ll send a SASE… I still have about 500 left.

UPDATE: Sorry! I’m always criticizing Acronyms…

Self-Addressed-Stamped-Envelope (sent to me, will return 5 LM317t’s…)

Terry King
152 Colby Road
West Topsham, VT 05086

But: 3 weeks till I get there from the Middle East…

Can you give me more info on using FET's with Arduino? Schematic(s), Maybe even some example code ;)

Maybe even some example code

analogWrite(pin, value);

Schematic(s)

use the PWM output filtered and into the gate
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

So I use Frequency dependent potential divider with low pass filter connected to a FET, and the divider is hooked up to Arduino PWM output pin? And if so, which FET should I use?

Frequency dependent potential divider with low pass filter

close:- Frequency dependent potential divider AS low pass filter.

which FET should I use?

Any one that will take at least 200mA (most will) and is a logic level FET. The FET will get hot because you are burning the excess voltage off inside it when it is not full on. The power dissipated will be with half the voltage dropped across it at what ever current the motor runs with only half the voltage across it. You might need a heat sink.

@Grumpy_Mike

Thanks! :D

I hope I'm not too annoying with all these questions :P, maybe something like this? http://www.nteinc.com/specs/2900to2999/pdf/nte2987.pdf

Could you also tell me what exactly am I look for? N-Channel MOSFETS?

maybe something like this?

Yes very meaty, that would do.

Alright! :)

Now, if only I could find that in Eagle :P

Rogy: @Grumpy_Mike

Thanks! :D

I hope I'm not too annoying with all these questions :P, maybe something like this? http://www.nteinc.com/specs/2900to2999/pdf/nte2987.pdf

Could you also tell me what exactly am I look for? N-Channel MOSFETS?

Mouser shows that at $7 a pop: http://www.mouser.com/ProductDetail/NTE/NTE2987/?qs=sGAEpiMZZMutXGli8Ay4kFfMPLZ9xW8yKOlRS6m%252bwN0%3D

Sparkfun sells a logic level N-channel power mosfet for a buck: http://www.sparkfun.com/products/10213

Lefty

I said it was meaty. :)

I found something a bit cheaper than the previous I linked and am not sure if it will work...

http://eu.mouser.com/ProductDetail/Fairchild-Semiconductor/FDP6030BL/?qs=sGAEpiMZZMutXGli8Ay4kBEMMAKgSkd8MdwkNnQ%2fGU8%3d

Hi,

Speaking Of FETS... I would like to decide best 2 or 4 power NFET and PFET to stock for use with Arduino...

I would appreciate your suggestions...

Two that have been suggested are:

RFP30N06LE "N-Channel Logic Level Gate Power FET" FQP27P06 "P-Channel Power FET"

Also maybe a good TO92 or similar small Logic-Gate NFET for cheap routine replacement of small NPNs like 2N2222 ??

What has been working well for you???

I'll make these available at a decent price in my online store...

Thanks!

Can anyone tell me what I must pay attention to when choosing a FET for using it to regulate voltage with Arduino?

Turn on voltage, it should be rated at 5V and have a low Ron at this value. At most 0.01R. It should be in a package that allows good power dissipation because as I said it will burn off the excess power.

@Grumpy_Mike

So: N-Channel FET, TO-220, 5V Turn on voltage, low on resistance, low resistance drain-to-source, and of course, drain source voltage high enough and same for current ?

Yes.

drain source voltage high enough and same for current

You will struggle to find one that is not high enough.

I think I found something that will fit my needs: http://eu.mouser.com/ProductDetail/Fairchild-Semiconductor/FDP7030BL/?qs=sGAEpiMZZMvECErq9cesgOhjwE8m5zTM4sOaJqrLpIU%3d

Now for the (hopefully) last question: How do I connect everything? :P

Something like this?

12V | |Source pin | |Digital Pin 9|----|Resistor|----|Capacitor|--Gate--|MOSFET| | |Drain pin | Load(Fan) | | | GND