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PWM Input with frequency >500Hz

Curtis Knischewsky 6 months ago in Master modules / MC4 • updated by Tim Reen 3 months ago 4

I am considering using an MC41 with PWM signals as inputs. These signals come from joystick thumbwheels on excavators made by a large multi-national OEM. My problem is the spec on the frequency of the PWM signal from the thumbwheel is 500Hz +/- 50Hz. I see the max allowable frequency from the MC4x catalog is 500Hz. Wondering if the MC41 will work with 550Hz PWM frequency input.

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It is a very good question. I think that the best way to explain it is to consider the value 500 Hz as the nominal value. 

The actual limit where the PWIM will fail to read the signal depends more on the "minimum pulse width", that we state to be 40 us. 

The limits for min and max MR is 3 and 97% respectively. These are hard limits in IQANdesign.

At exactly 500 Hz, a device with 3-97% output signal will mean the pulses last for 60 us or longer, which would give sufficient margin. 

At exactly 550 Hz, a device with 3-97% output signal will mean the pulses last for 54 us or longer, I think this is also acceptable margins. 

But if there for some reason is significant filtering on the output from the device, you might need more margins.


You should use IQANdesign 5.03 or later, in this version we introduced a de-glitching function to handle high frequency disturbances, see release notes

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Gustav,


First, thank you for the response.


This is great news. I am planning to test an MC42 with these joysticks in the coming weeks. I will post an update.

Hi...as per my knowledge the reason for configuring the output for open control PWM instead is if

you need to drive a current that is too far below the COUT operational range. On the IQAN-XA2, the COUT controllable range is 100-2000 mA.

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Hi Curtis,

We are supplying the MC41 (for extra attachment control) to dealears of a large multi-national OEM...

The PWM signals that come from the joystick thumb-wheels and foot pedals on these excavators work perfectly on the input side of the MC41 so you can go for it.