PWM issues when powering 4X 4pin 12v fan

[Nim]

Hello all:

I've bought a PWM generator like this one:


And I want to connect it to 4x 12V Fans with PWM connector but I'm having some issues. Basically I'm connecting things this way:



But I'm always getting the fans to rotate at full speed with no control at all. Also tried to disconnect the GND that connects the PSU to the FAN HUB, and I was able to control the fan but they stop and start, the speed is not constant. I also notice that where I should have 12V constant I get oscillations. If I measure between IN+ and IN - I get 12V but if I measure FAN1 between VCC and GND I get the same oscillations that I get measuring between PWM and GND. Am I having some ground issues?


Thank you all for the help!

 

[kellys_eye]

Are you changing the pulse WIDTH to regulate the speed or pulse FREQUENCY? It should be 'width' (i.e. the % setting). The frequency setting may also be applicable - have you got the spec sheets for the fans?

 

[Nim]

Hello,

I've left the frequency at 25Khz I'm only changing the duty cycle and if I have it connected like the schematic it does not work. If I disconnect the gnd that goes from the PSU to Fan Hub it works but the fan keeps speeding and stoping cause I have oscillating tension where it should be 12v constant.

The data sheets are these:

AFC1212D-SP19 pdf, AFC1212D-SP19 Description, AFC1212D-SP19 Datasheet, AFC1212D-SP19 view ::: ALLDATASHEET :::

AFC1212D-SP19 Datasheet, AFC1212D-SP19 datasheets, AFC1212D-SP19 pdf, AFC1212D-SP19 integrated circuits : DELTA - THIS SPECIFICATION DEFINES THE ELECTRICAL AND MECHANICAL CHARACTERISTICS OF THE DC BRUSHLESS AXIAL FLOW FAN. ,alldatasheet, Datasheet, Datasheet search site for Electronic Components...

pdf1.alldatasheet.com

 

[kellys_eye]

Is there an electrical path from the power (ground) pin to the signal output 'ground'?

Got a link to the PWM device you're using?

 

[Nim]

Hello, no there is not. The In- is not connected to the Out - on the Pwm Generator. Already tried to connect only the out- and out+ to fan Pwm but still no go.

This is the link:

MP12 12A 360W DC Motor Speed Controller Regulator PWM Motor LED Dimming DC6V-30V | eBay

Maximum power: 360w. 1 12A 360W DC motor governor without WiFi communication/with WiFi communication. Rated current: 12A. Liquid crystal display frequency and duty cycle, shutdown and output, clear and clear at a glance!

www.ebay.com

 

[kellys_eye]

Your schematic shows you using a BLUE wire for the PWM signal - if this is what you're doing then it's wrong as the PWM is supposed to attach to the YELLOW wire. The blue wire is a signal OUT of the fans for monitoring purposes.

 

[Nim]

In my case its the blue wire. The PWM is connected correctly. I manage to fix this using this circuit:

https://maker.pro/forums/threads/pw...fan-without-a-motherboard.289391/post-1773996

This way it works but with a little problem, when I put 100% duty the fan stops and at 0% it spins at max speed. It seems that I have a low active pulse and need a high active pulse. Already tried to use this:

How to Build an Inverter with a Transistor

In this project, we will show how to build an inverter with a transistor. This is a circuit which will give the opposite state on the output of the input signal fed into it.

www.learningaboutelectronics.com

But without luck. I've mounted this circuit using the inverted pwm as input but all I have now is 0% stopped, 1% or more full speed.

 

[kellys_eye]

I manage to fix this using this circuit:

Looks as if the PWM generator has an open-collector output hence the use of a pull-up resistor. The sellers information on the PWM device isn't specific on it's actual output hence my query about checking whether the -ve supply rail connects direct to the -ve PWM output. That it isn't connected indicates the open-collector situation but you should be able to get the right 'polarity' using the +ve output and the pull-up resistor.

 

[Nim]

Looks as if the PWM generator has an open-collector output hence the use of a pull-up resistor. The sellers information on the PWM device isn't specific on it's actual output hence my query about checking whether the -ve supply rail connects direct to the -ve PWM output. That it isn't connected indicates the open-collector situation but you should be able to get the right 'polarity' using the +ve output and the pull-up resistor.

The +ve and +ve output are connected internally. I've checked that using a multimeter. I've tried connecting the +ve output to a Pull up resistor but all I get is full speed on fan. Can you help me? Using the Pull up on ve- output I get the problem that at 100% fan stops and 0% spins fully. The ve- and ve- output are not internally connected.