I also looked a this tutorial (added the 180Ohm between Arduino and gate, to be safe, necessary?):
I connected PIN2 to the black LED Strip wire, PIN3 to - of a 12V power supply and the red LED strip to +of the same supply. This results in a switched off LED strip.
Now everything behaves strangely.
-When I touch PIN1, the behavior is quite undefined: It always lights but flickers. When I let it go, it might stay on or go off. If I touch it again, it may or may not change.
-When I connect PIN1 to - of the 12V source, it goes off. (That's what I expected), also after I disconnect.
-When I connect PIN1 to + of the 12V source, it goes on. (That's what I expected). After I disconnect, Is again undefined: It stays on, flickers, might even go brighter than before (Why didn't it have max brightness before?).
When I connect PIN1 to an additional 5V source with no connection (like common ground) apart from the 230V-side of the supplies, the strip lights independent of the fact if I connect to + or - (which would equal HIGH and LOW from an Arduino wired like the linked sites). After disconnection, again undefined.
With 5V with common ground, it never lights, independent of + or -.
So, what's my mistake? Wrong MOSFET? What's the characteristic part of the datasheet that makes this possible with IRLIZ44N, but not with irfz44n? I have to admit, I don't really understand MOSFET datasheets ...
Hi , First I will check some calculateions of risetime of the gate and the current for driving the gate of the MOSFET:
RC = 300nF * 1800ohm = 540us gate risetime
i = c dv/dt 300nF 5/.00054 = 2.8mA gate current
The pinout is expected to be confirmed by you:
pin 1: gate
pin 2 : drain
pin 3 : source
230 volts can ruin the MOSFET. Touching the gate with your hand can ruin the mosfet if static electricity is on your hand and you did not ground your hand before touching the gate. Please tell about your grounding in a schematic with 230 volts, 5 volts and Arduino wired with a common ground.
If the PWM signal is too fast for the RC time constant of the gate, it will not get full 5v on the gate, The Vt threshold voltage can be 4 volts, so a 5 volt Arduino is only a weak driver for a MOSFET like that.
I think I start to understand. I tried that, that solves the "undefined" states (to off, obviously).
Now when I look closer als the firgures, I also see why I do not get full brightness at 12V or anything at 5V. I also see now the advantage of the IRLIZ44N.
There are still a lot of things I don't understand in the datasheet. Apart from most characteristic quantites: Why don't the figures show curves for higher D2S voltages with higher gate voltages?
What MOSFET would work to get near full brightness from 12V/48W with a gate voltage of 5V?
When comparing the data sheets i noticed that IRLIZ44N has has much higher sensitivty than theIRFZ44n.
Compare figure3(transfer characteristics) in both datasheets.
I
RFZ44n starts conducting at about VGS=4,5V and will need problably at least VGS = 7v to conduct properly.
IRLIZ44N starts conducting at VGS=2,2V and conducts fully at VGS=5V.
Since the outputs of the arduino are max 5V the IRFZ44n has a hard time doing its job. Rdson will have a very high value at that VGS. So the IRLIZ44N is a much better choice.
If you are stuck with the IRFZ44n consider the Totem-pole driver in the tutorial but increase the voltage to 8V or 10V (maybe even 12V).
Also in my opinion 180 Ohms for a gate resistor is to high. The IRFZ44n has a gate capacitance of 1470pF the IRLIZ44N has 1700pF, this givs a time constant of 265ns up to 300ns. A value of 10 Ohms would be much better. Otherwise the tutorials are correct.
nilton61:
When comparing the data sheets i noticed that IRLIZ44N has has much higher sensitivty than theIRFZ44n.
Compare figure3(transfer characteristics) in both datasheets.
I
RFZ44n starts conducting at about VGS=4,5V and will need problably at least VGS = 7v to conduct properly.
IRLIZ44N starts conducting at VGS=2,2V and conducts fully at VGS=5V.
Since the outputs of the arduino are max 5V the IRFZ44n has a hard time doing its job. Rdson will have a very high value at that VGS. So the IRLIZ44N is a much better choice.
If you are stuck with the IRFZ44n consider the Totem-pole driver in the tutorial but increase the voltage to 8V or 10V (maybe even 12V).
Also in my opinion 180 Ohms for a gate resistor is to high. The IRFZ44n has a gate capacitance of 1470pF the IRLIZ44N has 1700pF, this givs a time constant of 265ns up to 300ns. A value of 10 Ohms would be much better. Otherwise the tutorials are correct.
With a MOSFET driver chip you normally don't need gate resistors, the output resistance
of the driver is sufficient to limit current pulses. However if you parallel several
MOSFETs from one driver you need a resistor on each gate to damp down any
tendancy to differential oscillation.
