Expanding SKR 1.4 fan PWM controllers? Okayyyy, so I thought, let's venture out into creating a PWM expander. This is how far I got, and it works great with an Arduino Uno: [attachment 116611 IMG_POCO_F1_20200901_170525-01.jpeg] It's this schematic but with an IRLB8743: [attachment 116612 ebace371d54bf43031b6d466ec0f23aa.jpg] So I made a test setup and it works great, no voltage leaking through the little circuit and I can control the fan speed through PWM with an Arduino Uno, but when I connect it to my SKR 1.4 it doesn't work. I am using the P1_00 'PSU on' pin and have defined it in my pins in Marlin: // // Heaters / Fans // #ifndef HEATER_0_PIN #define HEATER_0_PIN P2_07 #endif #if HOTENDS == 1 #ifndef FAN1_PIN #define FAN1_PIN -1 #endif #else #ifndef HEATER_1_PIN #define HEATER_1_PIN P2_04 #endif #endif #ifndef FAN_PIN #define FAN_PIN P1_00 // PSU on connection with DIY MOSFET for ABS slow fan #endif #ifndef HEATER_BED_PIN #define HEATER_BED_PIN P2_05 #endif Also tried it as 'FAN1_PIN', but didn't make a difference. Note that I'm already using #define E0_AUTO_FAN_PIN P2_03 for the hotend cooling fan because I needed PWM on it to make it a bit more silent and I wanted it to turn of when the hotend was below a certain temperature. Somehow it doesn't want to turn on when setting for example M106 S200. I also tried selecting different fans in case it somehow thought this would be not FAN0 but FAN1. I double checked the wiring with the schematics of the board to make sure I was using the Sig (P1_00) and GND of the 'PWRDET' pins. The only thing that might be is that the PWRDET Sig pin has a pullup resistor: [attachment 116613 Screenshot2020-09-01at19.04.20.png] Does anyone know how to fix this? Should I try shorting out the 1k resistor in my schematic to compensate for the pullup/pulldown? (I still don't understand the pullup/pulldown concept completely). https://reprap.org/forum/read.php?13,876833,876833#msg-876833 Sun, 10 May 2026 10:20:40 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?13,876833,881581#msg-881581 Re: Expanding SKR 1.4 fan PWM controllers? https://reprap.org/forum/read.php?13,876833,881581#msg-881581
Quote
aleksandarpu
What do you do?
Do you short connect GND and signal pins (1 and 3 on diagram)?

Hi I'm sorry, it's been a while, I'll have to check out how I did it.. Sorry if my update was vague about what I changed exactly.]]> Ohmarinus Controllers Tue, 16 Feb 2021 09:58:20 -0500 https://reprap.org/forum/read.php?13,876833,880850#msg-880850 Re: Expanding SKR 1.4 fan PWM controllers? https://reprap.org/forum/read.php?13,876833,880850#msg-880850 Do you short connect GND and signal pins (1 and 3 on diagram)?]]> aleksandarpu Controllers Sat, 23 Jan 2021 12:40:07 -0500 https://reprap.org/forum/read.php?13,876833,876835#msg-876835 Re: Expanding SKR 1.4 fan PWM controllers? https://reprap.org/forum/read.php?13,876833,876835#msg-876835
If anyone has any remarks about my design anyway, let me know if I can improve on this and if it's actually safe to do. I'm still new to electronics and despite triple/quadruple testing everything I'm never a 100% sure if it's a good idea I'm having.]]> Ohmarinus Controllers Tue, 01 Sep 2020 13:15:41 -0400 https://reprap.org/forum/read.php?13,876833,876833#msg-876833 Expanding SKR 1.4 fan PWM controllers? https://reprap.org/forum/read.php?13,876833,876833#msg-876833 [attachment 116611 IMG_POCO_F1_20200901_170525-01.jpeg]

It's this schematic but with an IRLB8743:
[attachment 116612 ebace371d54bf43031b6d466ec0f23aa.jpg]

So I made a test setup and it works great, no voltage leaking through the little circuit and I can control the fan speed through PWM with an Arduino Uno, but when I connect it to my SKR 1.4 it doesn't work.

I am using the P1_00 'PSU on' pin and have defined it in my pins in Marlin:
//
// Heaters / Fans
//
#ifndef HEATER_0_PIN
  #define HEATER_0_PIN                     P2_07
#endif
#if HOTENDS == 1
  #ifndef FAN1_PIN
    #define FAN1_PIN                       -1
  #endif
#else
  #ifndef HEATER_1_PIN
    #define HEATER_1_PIN                   P2_04
  #endif
#endif
#ifndef FAN_PIN
  #define FAN_PIN                          P1_00 // PSU on connection with DIY MOSFET for ABS slow fan
#endif
#ifndef HEATER_BED_PIN
  #define HEATER_BED_PIN                   P2_05
#endif

Also tried it as 'FAN1_PIN', but didn't make a difference.
Note that I'm already using #define E0_AUTO_FAN_PIN P2_03 for the hotend cooling fan because I needed PWM on it to make it a bit more silent and I wanted it to turn of when the hotend was below a certain temperature.

Somehow it doesn't want to turn on when setting for example M106 S200. I also tried selecting different fans in case it somehow thought this would be not FAN0 but FAN1. I double checked the wiring with the schematics of the board to make sure I was using the Sig (P1_00) and GND of the 'PWRDET' pins.

The only thing that might be is that the PWRDET Sig pin has a pullup resistor:
[attachment 116613 Screenshot2020-09-01at19.04.20.png]

Does anyone know how to fix this? Should I try shorting out the 1k resistor in my schematic to compensate for the pullup/pulldown? (I still don't understand the pullup/pulldown concept completely).]]> Ohmarinus Controllers Tue, 01 Sep 2020 13:05:54 -0400