Measuring PLC??

anismzs

Member
Join Date
Jul 2015
Location
Singapore
Posts
11
Hey Guys,

Apparently i need help for a project of mine. I am unable to continue as i am stuck with the Grafcet Process.. So, The operation goes like this..My project is about a automated rubbish collector.

I have the rough idea for the grafcet...the problem is , I am wondering if there is a PLC function that will allow me to measure distance? .. the thing is , when i first start operation , the gripper that will be gripping the part has a sensor to detect whether bin has been gripped or not , and after the throwing process , i need to return the bin to its original location , but how can i do that if i dont know the distance between my vehicle and the bin?...if i give the output for gripper to extend , it will extend to the fullest , and that is what i don't need.

i am not allowed to use Timers.
Please Help :(
 
The PLC cannot measure anything. It can however interpret signals from other devices. You might be able to use an encoder, or an ultrasonic or laser distance sensor, or just plain limit switches. Hard to say from your description. What "Throwing Process"? You might need something as advanced as a vision system if you are pickup up a thing, throwing it across the room and then trying to return it to its original location.
 
the whole operation is like this , Firstly ,i extend the Telescopic then i grab the bin , which will tell the PLC it senses it then the Telescopic goes to Home Position, after that the dumper activates and begin to dispose the rubbish into the truck , after that is done , it needs to return the bin to its exact location , but the problem is , i do not know how to determine the location of the bin , as the telescopic can extend to the fullest and still not know where's the location. Please Help :)
 
the phrase at the end says it all... "I am not allowed to use timers"
this signifies that this is a school project
and as such you.need to show us what you have already tried and what's not working as well as information on plc type etc.
 
the phrase at the end says it all... "I am not allowed to use timers"
this signifies that this is a school project
and as such you.need to show us what you have already tried and what's not working as well as information on plc type etc.
Hi DwSoFt, Yes it is , This is my 2nd project assigned to me , i have not started anything except for Grafcet which is still incomplete ..The project was just given.. Um PLC type would be the MELSEC QnUD type?..I wasn't really not allowed to use timers , i was told timers is close to the solution of the problems i have now , I only learned Timers , Counters, Master Control (Briefly) in School , Which is why i do not know if i can measure something with the PLC or anything for that matter. I hope i got the correct type of PLC.
 
The PLC cannot measure anything. It can however interpret signals from other devices. You might be able to use an encoder, or an ultrasonic or laser distance sensor, or just plain limit switches.

Many factors come into play with this scenario.
Is it used on stationary or mobile equipment? If the answer is mobile then the encoder might not be the best choice (in a real world environment of course) due to fragility and cost of upkeep.
On the other hand, if the bin must be returned to the exact same position, maybe a linear encoder or robust limit switches may be the best choices.

This is just me, but I would use an encoder for the finer points and limits for safety backups to prevent potential damage in case of encoder failure...which I have seen happen many times. If I'm reading too much into this I apologize everyone.

Regards,
Jay
 
Many factors come into play with this scenario.
Is it used on stationary or mobile equipment? If the answer is mobile then the encoder might not be the best choice (in a real world environment of course) due to fragility and cost of upkeep.
On the other hand, if the bin must be returned to the exact same position, maybe a linear encoder or robust limit switches may be the best choices.

This is just me, but I would use an encoder for the finer points and limits for safety backups to prevent potential damage in case of encoder failure...which I have seen happen many times. If I'm reading too much into this I apologize everyone.

Regards,
Jay
Hey Jaywillnot, It is on a mobile , like a truck ..so the solution is to get encoders or limit switches... But i don't have to do any programming ? .. Because my project is Programming , Do grafcet , Convert to Ladder Diagram and then finally test it on the actual machine. Thank You
 
On the extension arm you will need an encoder (thast can be as simple as an old mouse with a ball in the bottom.
or make two contacts that are making an encoder.
 
On the extension arm you will need an encoder (thast can be as simple as an old mouse with a ball in the bottom.
or make two contacts that are making an encoder.
Dear Shooter , Can you elaborate furthur ?.. Are you saying that i use 2 contacts to simulate an encoder?

Thanks
 
anismzs,

The main key is that you need a system that gives you an indication at witch position you get to the bin, so you need to know how far your telescope has traveled. Of course we don't know how your telescope is driven but if it moves, for instance, by a spindle, there must be an electric or hydraulic motor that rotates.
With a limit switch or a proximity switch you can count the amount of revolutions of that motor, and that gives you an indication of the distance traveled ( in pulses per mm or whatever distance you want)
A more expensive way can be a led or laser distance sensor that gives you an analog or digital signal that represents the distance.
 
Dear John.S, Thank You for your reply...

I could get a limit/proximity switch or sensor for that purpose , Probably best anyway haha , you guys are amazing :) , I think i didn't make my project clear enough , sorry about that , i am only doing the PLC Programming for it , So i am stuck with knowing what function to use , BUT as stated by RDRAST here , He says it is not possible , Is my teacher playing games with me or what ...cause i cant figure it out ...the closest solution i came up with was Retentive Timer ..But Timers are close but not the answer.
 
your instructor may be looking for a "knobble strip" with a proximity switch to read the knobbles .
When the telescopic arm is extended to pick the bin , the number of pulses from the strip are counted and the final count stored . After the bin is emptied and before replacing the bin i.e. in home position , the counter is reset and the arm is then extended till the new count equals the stored count .
 
Hi Pal , Thanks for the reply , To be honest , i've not heard of "knobble strip" before ...but from what you're saying , i can roughly guessed what you mean , Later today my Instructor will be telling me how to do it as i've been stuck for more than a week haha , Will tell what my instructor says later.
 
yes you can make an encoder with 2 switches.
and if you mount them with this knobble strip i like the word) you can make a digital distance sensor with cheap stuff.
You can also use arduino stuff cheap and easy.
 

Similar Topics

Hi, I need a program for measuring the current consumption of Equipments ( Pumps, Compressor,etc). and data logging of these measurement should...
Replies
13
Views
3,937
I'm trying to measure speed using a pulse sensor that is connected to the click plc, and this plc is connected to c more micro touch screen where...
Replies
1
Views
1,578
Hi guys, I want to measure the length of a piece of cloth that is produced by a machine using an encoder and a mitsubish FX PLC. I don't really...
Replies
2
Views
2,631
Hello All, I have a need to monitor and record uptimes for both PLC & SCADA systems, this is to be used as a performance measure for our...
Replies
6
Views
3,172
What would it take to build some PLC logic to measure amperage of a load (3 phase, 20-30 amps under normal load), and do something with the PLC...
Replies
11
Views
2,797
Back
Top Bottom