LM317 Help

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


I said it was meaty. :)

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



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...


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.


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 ?


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

[quote author=Terry King link=topic=62088.msg449378#msg449378 date=1306265151] 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. [/quote]

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

Thanks, Terry.

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

Thank you! :D

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

Under Terry's name it says "Red Sea/Saudi Arabia" so my guess would be "no."

For the divider I'm not sure if 1k resistor and a 18uF capacitor will suit my needs...

For the fan control I will be regulating 12V, the voltages which will be "available" for the fans are: 7V, 8V, 9V, 10V, 11V, 12V and will be changed as the temperature of the CPU Changes. I'm expecting the voltage change to occur no higher than 2x a second.

For the divider I'm not sure if 1k resistor and a 18uF capacitor will suit my needs...

I am not sure where you got these values from. An 18uF capacitor is very non standard, 10uF , 16uF and 22uF are the closest values. However, it is not very critical as it is only a second order filter and the slope here is not steep.

You will have to experiment as to what PWM values you have to get to give those voltages to the fan. This is because you are relying on the non saturated part of the curve and it is not consistent from device to device.

I'm currently "worried" so to say about the divider.

Will it allow me to change the voltage 2x a second?

1K and 18uF is a time constant of :- 1 103 X 18 10-6 = 0.018 seconds So yes it will not hamper a signal at 0.5 seconds period.

Ok, so I finnaly got my hands on all the parts I need, but there’s a problem… It’s not working :frowning:

When I tap the FET the fan starts spinning and if I don’t do that nothing happens…

I’m guessing that the FET is damaged, but am not sure…

What do you think?