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Identifying Faults with Danfoss Hardware Pump Function Blocks

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I am trying to use the Danfoss 40 series and 90 series pump control function blocks to control EDC's for hydraulic functions.  I'm using a J1939 joystick as the input device.  When I manipulate the joystick, I can measure a small output on the relevant wires for roughly 1/2 second, then the output immediately drops to zero and stays there until I power cycle the controller.  After a power cycle, I get the same 1/2 second of output, then zero again.

I feel like this must be caused by some fault detection either within the function block or the controller itself.  I have disabled fault detection in the function block by changing the boolean FltDet value to false.  I'm not sure what else could be causing this.  I came in this morning hoping that I could use the fault manager function block to determine what type of error is causing this behavior, but when I started reading the documentation for the fault manager, I started to suspect that this function block is for something much more complex.  I'm not trying to set up custom faults.  I just need to figure out why my controller is cutting off output to my pump EDC's.  If anybody has advice on the quickest and simplest way to figure this out, I would be extremely appreciative.

Thank you in advance.


Is the output from the function block cutting off or is it the output pin on the controller cutting off? If it is the function block not sending a value out, then I would suspect the parameters for the block are incorrect. If the block is outputting a value (even after 1/2 second) but the output pin is cutting off, I would check the status of the output pin and see what the bit coded value is. The status of the output pin can be found in the Inputs Page.

Hope that helps. I don't use the function blocks you are referring to, but that is where I would start.

Thank you very much for the suggestion, Beezkneez!

I added checkpoints to measure outputs directly from the hardware function blocks, and they are dropping to zero after half a second.  I changed the FltDetectTm value to 2 seconds(the maximum) and now I get 2 seconds of signal before the output drops to zero.  It seems the problem is with the hardware function block itself.  Even though I have fault detection disabled, the function block is still detecting a fault and setting the output to zero.

I'll do a little more checking to make sure I don't have something configured incorrectly within the hardware block.  If I can't get these hardware blocks to function, I guess I'll have to figure out another way to drive the pumps.

Wish I could help you further but I do not have any experience with the function blocks you are using. At least you have narrowed it down to the function block itself!

Taking a look at the documentation for the series 90 EDC block I see there is a status port which will give you a detailed explanation of any faults that occur within the block. I'd probably check the value of the status port after the output is cutting off. If that is the FB you are using, that is.

I have always used my own logic to create the output signal then PWM output drivers for to the output pin to control our pumps.

Thank you again for the suggestion. 

After speaking with one of the programmers at our Danfoss distributor, I decided to throw out the pre-made hardware function blocks and build my own.  They have half a dozen programmers, and he said none of them use the Danfoss hardware blocks because they include too many unnecessary features and are prone to errors. 

After a few minutes of tinkering, I was able to build my own logic to run the PWM outputs.  However, I'm getting full signal in one direction and only 25-30% of the end current value in the reverse direction.  I'm not sure why that's happening, but I'm guessing that the A output pin is not properly sinking the current when it's flowing in the B to A direction.  If you feel like sharing a screenshot of your basic bidirectional PWM pump control, I would love to see it.  I totally understand if not. 

Thank you again for the help!

****Edit:  A little bit of searching led me to this thread, which shows a good example of a bi-directional PWM driven circuit that is nearly identical to the one I built.  I'm guessing I've got something set up wrong with the outputs as I was trying to use them all in PinConfig 4 instead of using the H-Bridge pin configuration 8.


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