The yellow graph is the PWM signal (50% duty cycle and period \$ 3\tau=30ms\$) and the purple one is the speed of the motor. - //#define FAN_SOFT_PWM and #define SOFT_PWM_SCALE 0 - are the lines to look for. They only make this noise when not running on 100% fan speed. Pin16 is used for LCD panel. #2 dc42, May 10, 2018. gonzalo Well-Known Member. Figure 7. I'm running a SKR mini E3 v1.2 with Marlin 2.0.3 The PWM period is now \$ 0.1\tau=1ms\$ and duty cycle is still 50%. The fan works if it's connected to fan 1-3 slots, so the fan is working. If the fan is mechanically good and there is still noise, then it is the PWM frequency emitted by the fan. As you can see, the speed of the motor swings widely because the frequency of the PWM is not high enough. The issue is the way pwm works. Circuit for driving a fan with high-frequency PWM. In Marlin, it will be a setting ... You may need to experiment a bit. I have Prusa i3 Pro B Acrylic with GT2560(bought in September) and use Marlin firmware. Would this also impact the hotend and heated bed performance, or is the fan PWM separate? I assume it has to do with math and frequency. 12v fan with a buck converter and ground to the fan. Is this fixable by increasing the PWM frequency in Marlin? I'm trying to add a cooling fan on PWM but it doesn't work. So in theory we could run. // If all hotends and bed temperature and temperature setpoint are < 54C then the BLUE led is on. Unfortunately, hardly anything has changed in the result. // Increase the FAN pwm frequency. Figure 7 depicts the circuit used for high-frequency PWM. I had thought the 32bit board may be at too high a PWM frequency so tried to lower. The external control circuit is simpler with high-frequency PWM, but it can only be used with 4-wire fans. Removes the PWM noise but increases heating in the FET/Arduino //#define FAST_PWM_FAN // Temperature status LEDs that display the hotend and bet temperature. (3) FAN_KICKSTART_TIME set to 1000 (also tested 0,100, 500) , All work but do not improve control of fan. Removes the PWM noise but increases heating in the FET/Arduino // #define FAST_PWM_FAN // Temperature status LEDs that display the hotend and bet temperature. 50% 24v pwm is not the same as 50% 12v pwm. (2) FAST_PWM_FAN enabled, but could not test as compiler said not implemented yet. I don't fully understand pwm and fan speed, but from my basic understanding is the boards pulse the ground wire. The Ultimaker board uses pin 7 to control the fan speed, but this pin has not a 12v maximum tension, instead it gets it power … Pin 7 is set to PWM and it's not working. // Increase the FAN pwm frequency. There is 1C hysteresis. That's why I developed this hardware solution. No difference. // Otherwise the RED led is on. I have checked all these options. The following is my code for the fan that is at the bottom of your config.h . Although these fans are relatively new to the market, they are rapidly becoming more popular. The Marlin firmware offers several options to reduce noise by software. Now let's increase the PWM frequency. The following requirements are measured at the PWM (control) pin of the fan cable connector see Figure 7 and Table 1: PWM Frequency: Target frequency 25 kHz, acceptable operational range 21 kHz to 28 kHz Maximum voltage for logic low: VIL = 0.8 V Absolute maximum current sourced: Imax = … THE PROBLEM: on my board the pin dedicated to regulate the fan speed (via pwm) gets its current from an unregulated source. Also, If i turn up the fan speed on the ramps when running a print, nothing. Try a lower PWM frequency. I sent M106 code from Repetier but nothing happened. Speed, but from my basic understanding is the fan works if it 's not working following! 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