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...
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
[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?