issue with gravity mosfet as PWM
ankou29666 2018-08-04 23:17:46 2299 Views1 Replies Hi
I wanted to make an assembly from a DFR0457 module but stuff don't go the way I expected.
I power up the module from a 18V battery and send a 66% pwm signal (170 value) from an uno.
But I also measure 3.2V at the signal pin which is correct.
If I lower to 33%, I get 14.5V or so at output, and at 25% that gives 12.7v which is close enough from what's desired.
Other thing that surprises me, is that I always get battery voltage at output when there is no load and the voltages I told are measured with a small fan+schottky diode as a test charge. When I put my voltmeter at output of an unconnected pwm pin of the arduino, I always get 5v divided by duty cycle.
Am I doing anything wrong ? I'm unsure, I currently got no oscilloscope for troubleshooting, but feel like the optocoupler makes the mosfet working in linear mode instead of commutation. As far as I understand EL357N optocoupler should be able to deal with such low frequency. There's no capacitor anywhere and the
Which as far as I understand is not supposed to happen as module's datasheet says it can work up to 1kHz while arduino pwm work at 490Hz, so there should be no issue with this.
So can this module really work with PWM signals ?
I wanted to make an assembly from a DFR0457 module but stuff don't go the way I expected.
I power up the module from a 18V battery and send a 66% pwm signal (170 value) from an uno.
Code: Select all
I was expecting to get 12V at output but ... I measure 19.2V, which matches the battery's voltage (just out from it's charger).void setup()
{
pinMode (11, OUTPUT) ;
analogWrite (11, 170) ;
}
But I also measure 3.2V at the signal pin which is correct.
If I lower to 33%, I get 14.5V or so at output, and at 25% that gives 12.7v which is close enough from what's desired.
Other thing that surprises me, is that I always get battery voltage at output when there is no load and the voltages I told are measured with a small fan+schottky diode as a test charge. When I put my voltmeter at output of an unconnected pwm pin of the arduino, I always get 5v divided by duty cycle.
Am I doing anything wrong ? I'm unsure, I currently got no oscilloscope for troubleshooting, but feel like the optocoupler makes the mosfet working in linear mode instead of commutation. As far as I understand EL357N optocoupler should be able to deal with such low frequency. There's no capacitor anywhere and the
Which as far as I understand is not supposed to happen as module's datasheet says it can work up to 1kHz while arduino pwm work at 490Hz, so there should be no issue with this.
So can this module really work with PWM signals ?
2018-08-09 00:53:16 Ok i have read schematics again after reading another quite similar post and I believe R2 and R3 are way too high values for commutation. ankou29666
ankou29666 