Fan Control with PWM over existing EXISTING PWM fan output?

Thread Starter

AGreatson

Joined Aug 22, 2020
3
Hello,
First post after many many hours of GOOOOOOOOGLE and searching here.

Situation:
I would like to use the output from an existing PWM fan port which is relatively low current to drive a higher current load (see pdf attached BTT SKR MINI E3 V2.0-PIN.pdf FAN 0 and FAN 1 - PC6 and PC7).

The control options from the current PWM are quite good but the DC current handling is relatively low.

I purchased a small dual NPN mossfet array from amazon thinking it could simply relay the output from the existing PWM signal.
However when I installed the device, the larger load is simply activated fully regardless of PWM state and seemingly regardless of which original fan pin I attach the trig/pwm input on the FET.

There's also an LED onboard the PWM fan source which lights up indicating to me that there's somehow back current.

I don't know how to proceed.

I was thinking maybe I need some transistors inline on the signal because it seems to drive the led which means perhaps there's a ground path which effectively "turns on" the FET.

Any interested in helping a noob out?
TANKS!
Here's the FET: https://www.amazon.com/ARCELI-Trigger-Switch-Regulator-Control/dp/B077TX1J44/ref=pd_rhf_se_p_img_5?_encoding=UTF8&psc=1&refRID=2GDK740BXCHNEPRHZ4ET

And here's the board : https://www.amazon.com/BIGTREETECH-Upgrade-Control-TMC2209-Creality/dp/B0882QGFZR/ref=sr_1_1_sspa?dchild=1&keywords=skr+mini+e3+v2.0&qid=1598130024&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE2RjFLSlU1TEg2SDkmZW5jcnlwdGVkSWQ9QTEwMjEwNDQzUVYySURXVzJKTzYyJmVuY3J5cHRlZEFkSWQ9QTAwNjIzNjExS1FRNVM1MFVORlJTJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==
 

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Last edited:

sghioto

Joined Dec 31, 2017
1,451
I think you need a ground or common connection from the main board to the FET module. Try connecting pin1 of the fan port to the input of the module and connect the "ground" connection back to ground on the main board.
SG
 

Thread Starter

AGreatson

Joined Aug 22, 2020
3
SUCCESS:
I ended up connecting the Trigger of my FET module to FAN0 at the junction of the two resistors R70 ad R71 (fan 0).
Wired the rest of the module as you would expect with supply voltage and load connections.
Full PW control.
 

soyez

Joined Aug 17, 2020
51
Hello,
First post after many many hours of GOOOOOOOOGLE and searching here.

Situation:
I would like to use the output from an existing PWM fan port which is relatively low current to drive a higher current load (see pdf attached BTT SKR MINI E3 V2.0-PIN.pdf FAN 0 and FAN 1 - PC6 and PC7).

The control options from the current PWM are quite good but the DC current handling is relatively low.

I purchased a small dual NPN mossfet array from amazon thinking it could simply relay the output from the existing PWM signal.
However when I installed the device, the larger load is simply activated fully regardless of PWM state and seemingly regardless of which original fan pin I attach the trig/pwm input on the FET.

There's also an LED onboard the PWM fan source which lights up indicating to me that there's somehow back current.

I don't know how to proceed.

I was thinking maybe I need some transistors inline on the signal because it seems to drive the led which means perhaps there's a ground path which effectively "turns on" the FET.

Any interested in helping a noob out?
TANKS!
Here's the FET: https://www.amazon.com/ARCELI-Trigger-Switch-Regulator-Control/dp/B077TX1J44/ref=pd_rhf_se_p_img_5?_encoding=UTF8&psc=1&refRID=2GDK740BXCHNEPRHZ4ET

And here's the board : https://www.amazon.com/BIGTREETECH-Upgrade-Control-TMC2209-Creality/dp/B0882QGFZR/ref=sr_1_1_sspa?dchild=1&keywords=skr+mini+e3+v2.0&qid=1598130024&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE2RjFLSlU1TEg2SDkmZW5jcnlwdGVkSWQ9QTEwMjEwNDQzUVYySURXVzJKTzYyJmVuY3J5cHRlZEFkSWQ9QTAwNjIzNjExS1FRNVM1MFVORlJTJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==
yes you should go for some transistors
 

PathogenIX

Joined Oct 14, 2020
18
Can you explain if/how you managed to solve this? Currently trying to get a 24v pwm to control a 12v solenoid. Any schematics etc would be greatly appreciated. Have a current schematic for a drive circuit but yet to get it working. Happy to share with you if you're still struggling and fancy a crack at it.
 
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