Z-speed switch

[grobertson]

This is a lot of good info.I'm going to get out there and see if i can put it to use. thanx guys.

 

[ArikBY]

For Zero speed you dont need high speed counter when the motor On you dont do any thing when the motor is OFF start to detect your input.
See above.
Pat attention for safety issue you need to use proper device.

 

[elevmike]

ArikBY

What in the world did you do to this thread?

 

[ArikBY]

Mike

I made it simpel as it should be and as grobertson ask "simpel zero speed"
In the industrial laundry machine they use sensor with bulb of mercury with two sliping rings on the shaft and only when the shaft in zero speed the the mercury cover the contact and the door can be open.50s technology but still work.

 

[Rick Densing]

Arik-

I think he meant the giant picture. We don't all have 1 meter monitors!

 

[ArikBY]

Rick

I have 15" screen. I dont know why my picture so big.
Sorry if it bother somebody but I canot do nothing about.

 

[rsdoran]

Maybe we can resize it a little

 

[Rick Densing]

Rick

I have 15" screen. I dont know why my picture so big.
Sorry if it bother somebody but I canot do nothing about.

I think it was meant in fun.

 

[elevmike]

The 1st picture didnt show up on my PC just the big wide post.

Thanks ron, I've got it now.

Mike.

 

[oldgearhead]

We need to keep in mind the reason and possible reasons for zero-speed switches. ArikBy's response for control of one motor on one
machine cannot apply to very many examples. What happens when: The motor's overload relay trips? The chain breaks? The gearbox croaks?
The belt comes off?

To create PLC zero speed switch:
1) Get control of your input pulses.
2) Be able to count your input pulses.
3) Use two timers or counters (positive/negative)
4) OR the timer/counter outputs.

Quite often the $150.00 switch is the best solution.

 

[ArikBY]

I can agree it better to be in control all the way.But when you have limitation like high speed counter you can bypass it like I did.
If you have overload tripped motor output go off.
motor on shaft off fault.
The most important when I raise the signal shaft is stall it in stall position.
To use 2 timer or one you will have a same result.

 

[Terry Woods]

It ultimately boils down to how soon you really need to know that the flag is not turning AND how fast the flag is turning to begin with.

One big question is, where is the detector and flag relative to the particular device that is being subjected to the zero-speed question?

grobertson gave no indication as to the relative location in the process.

The fact that one pulses at 90 Hz while the other reads at 50 Hz means that the two effects will "migrate" across each other eventually.

It is certainly true that if the pulse is of a short enough duration the pulse might not be detected for quite a while. However, if the pulse is mechanically extended by making the flag 180-degress (or some such) then the occurance of the cross-over (migration) and detection becomes that much more detectable. Again, the question really is, how soon does the zero-speed really need to be detected?

And again, the answer to the question depends on the location of the pulse generator.

So...?