sasquatch
Member
What is the best way or products to use in order to monitor a variable resistance and control a motor speed?
ohmmeter
- Thread starter sasquatch
- Start date
danw
Lifetime Supporting Member
what range of resistance?
Is it floating or grounded?
Is the resistance likely to voltages induced in it?
Is it floating or grounded?
Is the resistance likely to voltages induced in it?
George Graziano
Lifetime Supporting Member
Look at Action Instruments.
http://www.inotek.com/Catalog/actionap.html
0-100 ohm or 0-100000 ohm to whatever
George
http://www.inotek.com/Catalog/actionap.html
0-100 ohm or 0-100000 ohm to whatever
George
There are several ranges of resistance. A few of the ranges are like these 200 to 300 ohms, 900 to 1100 ohms, and 4000 to 6000 ohms at the most. It should be in reference to ground. However, their is some occasional transient voltages which will trick a hand held ohmmeter. Actually, its more like a polarity problem in which I will have the turn the ohmmeter in one direction, then switch leads, write both numbers down, add them together, and divide by two in order to get the correct ohms. This only happens once in a while at random times and on random machines. I can turn the power off and its still there. I have to unplug the machine to get rid of it. I know to check for this occurance when the ohms are way out of speck. Like 50 ohms or more on lower ranges. I suppose that I could program if then statements into the plc. Anyway, I haven't got any plc's yet, but Im expected not to make mistakes, so all that I can do is to try and get some advice. Thank you for responding.
rsdoran
Lifetime Supporting Member
sasquatch said:
Has not been explained at all, you need to provide some details. You stated you have no plcs yet but mention programming if, then statements. Where does the resistance come from?
Start from the beginning, explain the system and devices if you desire assistance.
panic mode
Member
RTD transducer is the easy way to convert resistance (with range you mention) to an analog signal suitable for PLC or VFD inputs for example...
most devices will do 0-6000 Ohm, some will do higher such as 8 or even 12k (i think...).
most devices will do 0-6000 Ohm, some will do higher such as 8 or even 12k (i think...).
rsdoran
Lifetime Supporting Member
panic mode said:
I am game, he stated NO PLC'S AND no VFD was menioned.
SO why are y'all responding?
How do you respond before understanding the applicatuion?
panic mode
Member
Hi Ron,
not feeling good on father's day weekend?
try to relax and take it easy...
http://www.cartoonstock.com/newscartoons/cartoonists/dpa/lowres/dpan1132l.jpg
- i feel chatty, this is why i visit forums, where else should one feel free to ask questions and get answers?
- i can write anything i want, when i want
- it's not competition or paid service, i am just trying to help others and learn something here and there
- one thing i learned is that people are not exactly born with ability to ask questions
and many don't have that skill even after going to school for 12-16 years, it takes time
to realize that quality of answers depends on how well the question was formulated.
not everyone sees the link on top of page saying "New Here? Please read this important info!!!".
I think I saw it some 6 months or so after becomming member.
- he or she is obviously new member and has question(s). he may not even be aware that most common
(practical) way of changing speed of the motor is use of suitable drive. offering clues may help
get the better questions. he is a new member, give him a chance. post's like previous one are
most likely to just scare him away...
well...(clearing throat)... assuming this is complete and properly stated question...
...it's not taht easy. it takes factors such as will, imagination, time, computer access,
internet access, familiarity with browser, familiarity with english language, ability to
use keyboard, ability to convince wife that staying late at the computer is good thing
and that i'm not looking for certain type of web contect she doesn't approve and of course
sense of humor...
take care...
not feeling good on father's day weekend?
try to relax and take it easy...
http://www.cartoonstock.com/newscartoons/cartoonists/dpa/lowres/dpan1132l.jpg
- i feel chatty, this is why i visit forums, where else should one feel free to ask questions and get answers?
- i can write anything i want, when i want
- it's not competition or paid service, i am just trying to help others and learn something here and there
- one thing i learned is that people are not exactly born with ability to ask questions
and many don't have that skill even after going to school for 12-16 years, it takes time
to realize that quality of answers depends on how well the question was formulated.
not everyone sees the link on top of page saying "New Here? Please read this important info!!!".
I think I saw it some 6 months or so after becomming member.
- he or she is obviously new member and has question(s). he may not even be aware that most common
(practical) way of changing speed of the motor is use of suitable drive. offering clues may help
get the better questions. he is a new member, give him a chance. post's like previous one are
most likely to just scare him away...
well...(clearing throat)... assuming this is complete and properly stated question...
...it's not taht easy. it takes factors such as will, imagination, time, computer access,
internet access, familiarity with browser, familiarity with english language, ability to
use keyboard, ability to convince wife that staying late at the computer is good thing
and that i'm not looking for certain type of web contect she doesn't approve and of course
sense of humor...
take care...
leitmotif
Member
I personally find it difficult to ask an educated question when I have no idea of what I am asking about. Maybe that is why I am asking the question ie learn enough to enable me to ask educated questions.
To the guy who is asking the question
What does the motor do ie pump liquid (what is the stuff)
What does this resistance thingy sense liquid level, air temp, weight of powder etc etc. Tell us about your process
process moves XXx gallons, cubic feet, etc etc of material YYY
1. Tank full of whatever
2 Pump down
3 at low level stop pump
Dan Bentler
To the guy who is asking the question
What does the motor do ie pump liquid (what is the stuff)
What does this resistance thingy sense liquid level, air temp, weight of powder etc etc. Tell us about your process
process moves XXx gallons, cubic feet, etc etc of material YYY
1. Tank full of whatever
2 Pump down
3 at low level stop pump
Dan Bentler
I dont understand what is so hard to understand about the question. I am going to get a plc to control a motor speed based on a resistance input. Both the input and the output are analog. I know that I can get an analog output module to control the motor. All that I need for now is an ohmmeter input. Can I find a module that will do this or should I have an ohmmeter specially made which will hook up to a plc? Once I get that going, then I can ask some really good questions. Also, you have to realize that I cant give away company secrets no matter how much you try to pry them out of me. So, if you cant understand that, then the problem is not with me.
sasquatch said:
You will have to scale the input from a minumum to maximum value. The best way to aproach this is by exciting the resisitor; is it a pot? If you have three legs available you can connect your power supply to opposite ends of the resistor and connect the input (wiper) and the (-) or (+) side to your plc input. Once your range of variation is determined, you can scale it to engineering units i.e. 0-10000 or something like that. This min to max variation in voltage can be used in a PID as the PV (process variable); based on a Setpoint derived in your program or through operator input, you can then control your analog output as the CV or control variable.
This is all I can do based on the limited (non secret) information you have provided. I really don't think anyone here is trying to get proprietary information from you, but I could be naive.
panic mode
Member
sasquatch,
sorry to be the one to say it but this is still not nearly clear enough for complete answer.
so far we only know that there is some variable resistance and that this is supposed
to affect speed of some motor. no more no less...
It would be good idea to explain a bit more the type of resistance (what nature,
what is controlling it, is it isolated/potential free or already connected to something,
do you need isolation, what plc we are talking about, what range, how big is the
distance from "resistance" to PLC or transducer, is signal cable shielded,
there is no indication if the resistance is actual potentiometer or some media and
if this can be disconnected in normal operation or not, linearity etc.).
also we just have learned from your last post that that there is in fact a PLC with
analog I/O but again, that's all we know. it sounds like you have VFD but you still
didn't mention it clearly (not to mention that we have no clue what brand and model
of those PLC and VFD are supposed to be).
All of those can have impact on type of answer you will get. After all most people
here are busy professionals and as you have seen there is slight tendency to avoid
answering problems that are not clear enough.
as for propriatery information, keep it to yourself and try to simplify the problem. i don't think that someone here will get rich from reading your post if all you state is plc or drive brand, analog signal type and range etc.
sorry to be the one to say it but this is still not nearly clear enough for complete answer.
so far we only know that there is some variable resistance and that this is supposed
to affect speed of some motor. no more no less...
It would be good idea to explain a bit more the type of resistance (what nature,
what is controlling it, is it isolated/potential free or already connected to something,
do you need isolation, what plc we are talking about, what range, how big is the
distance from "resistance" to PLC or transducer, is signal cable shielded,
there is no indication if the resistance is actual potentiometer or some media and
if this can be disconnected in normal operation or not, linearity etc.).
also we just have learned from your last post that that there is in fact a PLC with
analog I/O but again, that's all we know. it sounds like you have VFD but you still
didn't mention it clearly (not to mention that we have no clue what brand and model
of those PLC and VFD are supposed to be).
All of those can have impact on type of answer you will get. After all most people
here are busy professionals and as you have seen there is slight tendency to avoid
answering problems that are not clear enough.
as for propriatery information, keep it to yourself and try to simplify the problem. i don't think that someone here will get rich from reading your post if all you state is plc or drive brand, analog signal type and range etc.
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milldrone
Member
Does this mean that you want to control the speed (VFD?) with a Potentiometer (or resistance value) now? Does this mean futher down the road you want to change the speed with a plc using a potentiometer (or resistance value) as a input to the plc? I think what is confusing the forum members is normally the output from the plc is either voltage or current and not ohms. Your posts imply that you want an ohm value from the plc. I have never seen an ohm value output from a plc (doesn't mean that one doesn't exist).sasquatch said:
If you can't answer this question because of company secrets then I don't think anyone here can help youpanic mode said:
This appears to state that you can get a module. Then two sentences later you ask if you can get one. Most of us here are confused by your description.sasquatch said:
If you are getting a ohm value from your process. All we need to know is the range of that ohm value. So that we can recomend a scheem that will work. We won't ask you for any details about how you are getting the value, if it will give away your secrets (although as a group we tend to be curious about these kinds of things). Even the most seasoned members on this forum learn something from answering questions here.
So , can you answer panic mode as to what kind of motor speed changing mechanism you have or intend to get? What plc you intend to use? After these questions are answered I'm sure there will be scaling questions, operator input (or recipe) questions. If you need answers to those I'm hoping we won't have to pry the details out of you.
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