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MC42 PWM HS+LS output overload
Does the MC42 perform an active LS diagnostic on PWM HS+LS outputs during startup, even when the application function group is disabled? We receive a Critical Overload on C1:39 with a SPAL ABL321P PWM output. Delaying the physical connection of the PWM wire until after startup completely eliminates the fault.
According to the manual, Appendix B (page 122) states that the check for an HS or LS short to the battery during startup has no contact? Or am I misunderstanding this?
Yet it does happen....
Customer support service by UserEcho
Hello Jesse.
The "No contact" is the message you would receive in a system that has a MC4x with this problem.
What happens if you short HS or LS to battery is that during startup you will try to power the unit trough those (back ending).
We detect that during the startup and the unit will not start the application.
This is to prevent a short circuit on an output starting the unit when it is not intended.
If you have the PWMOUT channel in a disabled function group you should not be getting any messages regarding that channel at all.
Have you checked that the channel is in a function group that is disabled from the start?
Meaning that you do not have any delays either in a channel or with the calculation order or anything like that before it gets disabled.
Do also keep in mind that the PWM/COUT are in pairs, A/B, C/D and so on.
So if you get overload on A you also get it on B, because they share high side driver.
But should still not get a error message if a channel is in a disabled group.
Hi Thomas,
Thanks for your response.
This function group is indeed disabled during startup.
This involves a PWM output (HS+LS) on an XC41 module, where a 15k ohm resistor is connected between C1:14 and C1:39 to prevent an open-load error. From C1:39, we send a PWM signal to the input of the SPAL fan.
I ran some tests that showed that when there is no power (12 VDC) applied to the fan, a voltage builds up on the SPAL’s PWM wire. When you then turned on the fan, this voltage disappeared.
We connected the SPAL as follows: a constant 12 VDC supply, and the PWM signal wire is now switched via a relay so that no voltage can ever be present on the PWM output.
However, we still occasionally encounter a problem with an overload warning on pin C1:39. Restarting the application resolves this.... This is the same DC motor as the one in the 5847006002 liquid cooler.
Do you often experience problems with this system?
The PWM outputs are not designed to be used as a "signal" output so there has been some problems when trying to use them as that.
Not specifically overload, more in line with not getting a readable signal in to the receiving controller.
But i have heard of setups that they made work.
This is how they said they set up their system.
But if i understand you correctly, you have a very similar setup.
A difference is that they can decide when the fan gets turned on with the DOUT.
Do you get the overload at any specific action?
Like when you go to 100% or 0%, or is it random?