I have a question regarding pwm and a logic level fet. In my project I am taking a pin off the arduino and trying to use it
to control a led array at different brightness.
My question is, it doesnt work unless the frequency is high. I was under the impression that 5 volts is just 5 volts and through
pwm this is on/off time is what controlled the "speed"
If I measure the output pin on the arduino, I get a maximum voltage of 1.3 volts at max frequency(100 percent duty).
As far as I know this is really just borderline on getting the mosfet to work. Here is a link to the datasheet for the device I thought would work. http://www.diodes.com/datasheets/ZXMS6004FF.pdf
If I am reading this correctly, to get current through that mosfet the "input voltage" or the gate as I think it would be called
would need to be at least 2 volts for the mosfet to work.
I can make the circuit work very well if I put 5 volts to the gate.
Am I going about this right? Is PWM really just an average voltage at the pin of the arduino so at 50% it is only approx 2.5 volts(which I have never seen on my circuit). Is there a better logic level fet for this application (pwm use, fully on at 1 volt)
My question is, it doesnt work unless the frequency is high.
Not a question a statement.
How do you know this if you don't know how to change the frequency?
So how have you wired it up?
Have you got a common ground?
What is your load?
If I measure the output pin on the arduino, I get a maximum voltage of 1.3 volts at max frequency(100 percent duty).
Measure with what? DVMs give very poor results on PWM signals.
That's not really a MOSFET, its a switching IC using a DMOS FET internally. It has
woefully slow turn-on and turn off times (60us to turn off - 3 orders of magnitude slower
than proper (VMOS) MOSFETs can do). VMOS devices have vertical current flow
across the chip, which means they are far superior, but cannot share a die with control
circuitry - hence this is a DMOS device.
Its 0.5 ohms, pretty poor for a switching device (but about the best DMOS devices can
achieve). Should sort of work at the default Arduino PWM rates though, but given the
package its likely to go into thermal shutdown for largish currents.