Author Topic: Display not showing RPM properly  (Read 4146 times)

Offline Mike AA

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Display not showing RPM properly
« on: August 12, 2016, 10:08:31 PM »
I have a DP200-00-01-03-00-00 that is getting fed from a MC024-020. The MC is reading a speed sensor ona toothed wheel on the output shaft of a hydraulic motor being powered off a S90 pump. The motor spins upto 1325RPM. I can watch this speed on the service tool and that is all the further it goes. The display shows completely random numbers than will sit at 249rpm then all over the place again down to 8rpm, the whole time not changing the speed. I am sending the data from the MC via can and receiving on the display via can. Am I going beyond the speed the DP200 is capable of?

Thanks
Mike

Offline FluidPowerTom

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Re: Display not showing RPM properly
« Reply #1 on: August 12, 2016, 10:39:01 PM »
The DP200 is just displaying the data that the MC is sending it, correct?  In that case then you couldn't be exceeding the DP200's capabilities.  Based on what you're saying I strongly suspect that there's a CAN communication issue.  My suspicion is that the way the data is being sent on the bus may be a bit mixed up or the way that the display is unpacking the data is inconsistent with how it's packed up by the controller.

Look over your CAN send and receive logic on the controller and display.  Maybe some bytes are flipped or offset or something.  Is it all unsigned data types, or is there a signed data type?  Maybe take screenshots of your send and receive CAN logic.
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Offline Mike AA

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Re: Display not showing RPM properly
« Reply #2 on: August 13, 2016, 12:08:39 AM »
HA! I had a signed 16 bit instead of unsigned feeding the split feeding the can_tx. I have to have a change to upload this program to the computer another day but I'm guessing that was the issue.

On a side note, shy of sending a T/F to the display  to show a negative value is there another way to send signed values to the display?
« Last Edit: August 13, 2016, 12:13:06 AM by mikeaa12 »

Offline FluidPowerTom

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Re: Display not showing RPM properly
« Reply #3 on: August 13, 2016, 12:13:24 AM »
Yep, it took me some testing to figure out what works in that respect.  What I do is a Retype from signed to unsigned (before the splitter if it's larger than 8-bit).  Then on the display side just do a Retype back to Signed after the combiner.  I'm usually using displays other than Danfoss, but I think this will work.
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Hydra-Power Systems - Distributor - Pacific Northwest