Fan PWM control with generic closed loop control works but!!

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Nijn
MS/Extra Newbie
Posts: 1
Joined: Fri Jul 14, 2017 10:29 am

Fan PWM control with generic closed loop control works but!!

Post by Nijn »

I have setup PWM fan control and it works correct when engine is started in 'cold' conditions.
If the engine is started when already 'warm', the fan control does not start what am I doing wrong?

Here is my configuration:

Part1 PWM regulation
One of the generic closed-loop PWM's is used to generate the PWM signal.
Output modulation between 50 and 100% of the speed (notice that the output is reversed)

PWM frequency is set to its max of 250Hz, this is much too low to drive the fan. Not good, motor will heat and make a lot of noise when modulating.
To increase the PWM frequency an Arduino mini is used. It reads the PWM signal and sends is out with the same modulation but on a higher frequency. (20kHz)
The PWM signal drives an H-bridge that on its turn powers the fan.

Part 2 start and stop the fan
The generic closed-loop PWM will make the fan run at all times (from 50 up to 100% as described in 1st part) .
A generic PWM or the programmable on/off outputs is used to start and stop the fan.
I made the configuration so the fan will start once the coolant is above 60°C and stop the fan once the coolant temperature is below 55°C.
The curve is straight linear so the output corresponds to the temperature.
The output of the generic PWM is used to enable the H-bridge module that drives the fan.

Problem:
The closed loop does not activate if the input signal (coolant temperature) is above the target when the MS is turned on.
Once the signal is equal or lower than the target, the loop is activated and the fan starts to run.

Is this a bug or is my configuration not correct!
Attached the screenshots of the configuration.
Fan control settings.pdf
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