Hi all, I have a problem that's getting me nuts. I have milled my first PCB, it's a PID system to control a heater for a 3d printer nozzle(has also NTC thermistor, fan+switch, LCD, rotary encoder). The system was working fine when on Arduino. Then I milled it and I think that something in the layout is generating a disturbance that crashes the 328. The LCD starts displaying odd characters and the MCU crashes or resets. This always happens soon after I activate the PWM control.
The PWM drives an NPN S8050 transistor, driving itself a IRFZ44N MOSFET, opening flow for a 40W 12V heater element. The problem became much more stronger when I started applying linear ramps to the PWM signal level in an attempt to smooth out possible spikes. And always crashes during a ramp up or down.
Below is the schematic, there are also two 0,1 uF caps between the 328 VCC-GND and AVCC-GND near the MCU that are not depicted. This discussion is very similar to this one https://forum.allaboutcircuits.com/...elf-if-i-start-pwm.160079/page-2#post-1397598 in which @BobTPH suggests the current is very high(50A) in his system. However I don't understand that calculation. In my case I have considered a maximum of around 3,3 A drawn by the heater. Do you have any suggestion?
View attachment 282150
The PWM drives an NPN S8050 transistor, driving itself a IRFZ44N MOSFET, opening flow for a 40W 12V heater element. The problem became much more stronger when I started applying linear ramps to the PWM signal level in an attempt to smooth out possible spikes. And always crashes during a ramp up or down.
Below is the schematic, there are also two 0,1 uF caps between the 328 VCC-GND and AVCC-GND near the MCU that are not depicted. This discussion is very similar to this one https://forum.allaboutcircuits.com/...elf-if-i-start-pwm.160079/page-2#post-1397598 in which @BobTPH suggests the current is very high(50A) in his system. However I don't understand that calculation. In my case I have considered a maximum of around 3,3 A drawn by the heater. Do you have any suggestion?
View attachment 282150
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