11/8/2019 11:26 AM | |
Joined: 6/22/2017 Last visit: 8/31/2023 Posts: 5 Rating: (0) |
Hi SOble, or anyone else that has experience with this :) What would you do in the case of 8 fans where each fan returns a pulse train on a different HS input? At the moment I made 8 interrupt OBs where I save the current counter and previous counter in a variable, and one cyclic interrupt OB where I calculate all fan speeds. I've attached a pdf that explains how I would do this. After studying the different types of fans that need to be tested, the feedback signal frequencies range are 100Hz and 250Hz (3000RPM, resp. 7000RPM). But this can change according to the product design. I was wondering how this would "affect" my user program, as each HW interrupt would "pause" my user program, and each input can come at a different time interval, I hope the CPU can process this. Practical example: a unit has 5 fans, which each give their speed feedback signal to one of the digital HS inputs. Fans can run at a slightly different speed, which means my hardware interrupts will come and go at different intervals. Obviously I do not want conflicts, so I hope the CPU won't be noticeably influenced by this. Which means I'm hoping for a very fast handling of HW OBs (range: µs). Also note that the fan speed measurement is only a part of the full test. I'm thinking of removing the cyclic OB and doing something similar with a square wave or something, I think this will be just as efficient but without a cyclic interrupt for the total test time. The fan speed test will only take a few seconds, maybe half a minute, while the full test of the units will take around 10 minutes. Worst case, I could "block" the input signals by using a relay for each fan, that would make it possible to measure each fan speed sequentionally. I'd rather not do this though. Thanks in advance! Kind regards Levi ------------------------------------------------------------------------------------------ AttachmentFan Speed Measurement.pdf (37 Downloads) |
Last edited by: Jen_Moderator at: 11/08/2019 12:27:48New subject after splitting |
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This contribution was helpful to1 thankful Users |
11/8/2019 1:31 PM | |
Joined: 5/6/2010 Last visit: 4/24/2024 Posts: 1963 Rating: (272) |
Hello Levi, here is another solution/suggestion. I would do this measurement not with relay and HSC input and more. You can use also
Then can you measure a lot of speeds without problems at the technology functions. regards |
11/13/2019 12:01 PM | |
Joined: 6/22/2017 Last visit: 8/31/2023 Posts: 5 Rating: (0) |
Thanks for your reply CaOd, but the transducers are no option anymore since we already have the PLC and DI HS modules. I use similar transducers for reading NTC temperatures, which are very nice (I love Phoenix Contact!). I didn't find out about those PWM transducers before I ordered everything, which is why I want to stick to the HS input solution (that's also the cheaper solution). |
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