Signal to programmable tachometer.

[Mike AA]

Hello I am new to the forum as a poster and have tried searching for anything I can think of to help me. I have been using plus1guide for about a year now off and on and have learned a lot about how to send out different signals and read sensors.

 I am working on a giant trencher that has speed sensors o the track motors feeding to an iomodule which is feeding to a wireless Bluetooth device and being received by a Bluetooth device in the cab then connected to the canbus of the controller, an MC050-018 I believe. I have no issues reading the speed sensors and putting to info on my display to show our speed, the gauge on screen isn't quite accurate but its close. They like having actual gauges showing everything in addition to my display until they're completely comfortable with the electronic display. I am having issues getting my isspro programmable tachometer mc8530 to operate with a signal from the controller. I would like to essentially output the exact same signal I am receiving. I will post code of what I have done so far shortly but wondered if anything needs has any suggestions? I have run a wire straight from the input to the output in code, I have run from input to a switch with just true/fasle or 5000 and 0. Nothing makes the gauge work reading the sensor speed. I believe I got the tach to work just sending a timed signal within the code to test.

Any ideas?

[dbrisendine]

What is the input type?
What output configuration are you using?

[Mike AA]

Sorry for the delayed response I got called away on another job.


The input is fed to an IO module on C1P09_MFin and read as a Freq and as a digital in. The freq is sent to a freq to rpm conversion for my digital readout of our traveling speed. The digital in is sent to a transition which then sends out to a digital out on MC050-018 C1P31_DigOut.

I am able to reliably read the speed so I know the input setup is working, I just cant get the output to work the way it should.

I have attached the current setup I tried, the input settings, the code and the output settings.

I was once trying to use the rpm output to feed a timer that would then do the pulses out to the tachometer but couldn't get that to work either.

[spittet]

I don't think the DigIn is fast enough to trigger a True value. Your PulsePerRev is 63 and I assume your shaft is running at a few hundreds RPM. This means that the DigIn will switch ON/OFF at least at a few kHz. This is simply too fast for the DigIn.

Sam

[Mike AA]

Yes the motor can be running at a few hundred rpm at maximum speed, we don't usually run anywhere near full speed but I need to have speed through the full band. So my best bet would likely be to come off the rpm side and use the value as a delay for a timer to turn Digout on as fast as the rpm is spinning, at least that's what I am thinking next.

[dbrisendine]

PWM output could be a solution for this.

As to the timer / delay firing a digout, this could function for your purposes.  The only drawback would be the accuracy / repeatability needed.  You would be limited to the scan time of the processor being the smallest change of state delay (similar to the digin not being able to 'respond' fast enough).  It is actually not the Input or the Output physically that is the issue but the delay of the updated processor's IO table and CPU logic scan.

[Mike AA]

I was thinking this might be an issue when I was looking at the port speeds and only MFP have faster access. Unfortunately I am using all 10 outputs to control 6 hydrostats. I will need to see if one only needs to go forward then I can steal the other half to feed the tachometer.

Thanks for the responses!

-Mike

[Mike AA]

I am back in a situation where I am trying to get this to work. I have a programmable tach and a counter hooked up to C1P46 of an MC050-018. I am reading signal from a motor spinning at upto 300 RPM with 30 pulses per revolution. I am able to read the speed reliably through an IO module to our display. Some of the guys would really like to have the counter and the tachometer showing the readout also.

The counter and tach both look for simply the pulses from a speed sensor (square wave). I setup a oscillator with a true and an on time of 1 ms and a period of 2ms. This should in theory give me 500 pulses per second and both my tach and counter should show 500. The tach is bouncing errractially which I am not worried about. The counter is showing me about 42 pulses, much less than I expected. This seems to be showing me that the port still cant handle the speed. The counter is capable of 10KHZ and when direct wired works fine but we are trying to get away from a mass of wires leading to an area where we already have the IO module and just power and data.

Any other ideas? I was thinking about getting a voltage to frequency circuit but I would really like to get this figured out with software on the MC.

Thanks,
Mike

[Mike AA]

I made some progress after thinking about how the outputs on the upper level pins are. I have a value of 10 constant connected to the output value of C1P45. I am using C1P24 as a frequency input just monitoring frequency and the two pins connected and then a lead connecting to my counter/rate meter. When I change the Group 2 ReqFreq in the outputs page my counter rate matches and C1P24 matches. I then went into the Group 2, disconnected the ReqFreq pin and put a SET in my program so I can manually change the value for the one pin instead of all 4. Here is where things no longer make sense. Once the program is loaded the ReqFreq apparently got a phantom number that matches the ReqFreq of the other 3 pins that are still connected. In a parameter page I try to set that value and it doesn't change.

Are outputs settings values only set at the beginning on power up or can I simply not split the pin off out of the group?

Thanks,
Mike AAlderink

[FluidPowerTom]

Mike, can you check what your cycle/scan time is on your MC050?  If your cycle time is, for example, 10ms then your 2ms logical oscillator isn't going to function the way that you want.  My recommendation is, if possible, to scale down your oscillator speed to something that the controller can calculate and make up for that in scaling your tach/counter display.  For example, make your oscillator 10 times slower in the MC050 and in the tach/counter display change the scaling accordingly.

[Mike AA]

FluidPowerTom,

The 2 ms oscillator was just a test to see if it could actually give me that speed. I have actually been experimenting with using the reqFreq for the group and tried splitting the pin from the  group but for some reason even if the wire isn't connected it still sets to whatever the group pin setting is.

I was looking up voltage to frequency circuits which I could use on an output pin then feed the frequency to my Counter/Rate meter.

Mike

[Mike AA]

My final determination is that I can get upto 4kHz but when I change the frequency it has to change all 4 ports connected in the group. i was not able to pull each port out of the group and set each port with its own frequency. I was able to reliably get both my counter/rate meter and the programmable isspro tach to read correct values but unless I want all 4 ports to show the same frequency it wouldn't work. I may get one of the voltage to frequency circuit boards but we are trying to get my boss to let us install another Display instead of a bunch of gauges and counters.

Mike

[BRIan]

The updated controllers (-1xx) now have the frequency changeable for each output individually. Remember, the minimum frequency is 33Hz.

[Mike AA]

Unfortunately i also found that issue with the minimum being 33Hz which was also way to high for measuring what could be as slow as 5Hz.

Thanks,
Mike Aalderink

[BRIan]

For frequencies <33Hz use the pin as digout and switch it on/off at the right rate using an oscillator