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Topic: LM317 Help (Read 13063 times) previous topic - next topic

rogy56

@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?

Grumpy_Mike

Quote
maybe something like this?

Yes very meaty, that would do.

rogy56

Alright! :)

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

retrolefty


@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

Grumpy_Mike

I said it was meaty.  :)

rogy56

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

TerryKing

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!

rogy56

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

Grumpy_Mike

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.

rogy56

@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 ?

Grumpy_Mike

Yes.
Quote
drain source voltage high enough and same for current

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

rogy56

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

justjed


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


Cool! Would 2 "forever" stamps be sufficient postage? Maybe 3 to be sure, eh?

Thanks, Terry.
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

Grumpy_Mike

No like this

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

The way you had it:-
1) the capacitor would block the DC signal and nothing would get too the gate
2) you would not get any more than 5V across your fan

rogy56


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