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