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