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Topic: Arduino Motor Control Issue (Read 1 time) previous topic - next topic

cl10Greg

That is correct.  Once it goes below 400 it just drops off.  That is a good point and something I should check.  I will check the pot response tonight and report back.  If that is my only problem then I will be pretty happy.  XD

cl10Greg

Resurrecting this post.  So I have all the analog signal working fine and reading.  I do have an interesting PWM issue though.  With that same BUK nmos I have been using, It actually turns on when analogWrite is at 0 and not at 255 like expected.  What would cause this?  Also, when the FET first turns out it does pass the 24V that I can see through my scope but as the PWM duty cycle increases it is only at 5V again where it should be at 24V.  Any ideas why the voltage saturates after it goes above an analogWrite signal of like 20?  Please help! :smiley-mr-green:

cl10Greg

I am doing all these test with an LED hooked up to the 24V source and being grounded through the NMOS.  So my observations are based on brightness and not on the motor response.  Changes the pull down resistor of the gate to a 1K seemed to make it brighter and more responsive.  I made a test program to start at 255 and decrease to 0 and sure enough at 255 it is off and the LED gets brighter and the voltage increases as it gets closed to 0.  Once it hits about 20 the voltage is almost at 24 but then we it goes down to about 15 the voltage drops out and the LED shuts off. 

cl10Greg

Here are some scope pictures and the setup picture.  A lot in one picture. 

cl10Greg

Any ideas on this and why the duty cycle would affect the DC voltage of the VDS?

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