motor moment project

perjan6666 · Jul 17, 2012

hi can anyone help me with design on a circuit board that will do the same as a 10kΩ pot?

The situation: I have a conveyor belt with 3 motors with gearbox,.

The problem is that the help engines do not have the same speed as the main engine.
So I would let the help engines hang freely from the shaft and attach an adjustable spring to adjust the torque.

Micro switches will give signal to the circuit board if the spring is too tight or too loose.

The circuit board must then change the resistance to the frequency converter for the motor to change the engine speed up or down.
that way the motor always give the same torque.

The circuit board must have an adjustable time delay so that the motor speed due not goes up and down all the time

Motors to day are controlled by a frequency converter that is remotely controlled by a pot 10kΩ

Thank You sorry for bad English - Google translate

alec_t · Jul 17, 2012

1) Does the pot have only DC applied to it?
2) What voltage does the pot have applied to it?
3) Is one terminal of the pot connected to circuit ground?
4) Are all 3 terminals of the pot connected to wires (i.e. it's used as a true potentiometer), or only 2 terminals (i.e. it's used as just a variable resistor)?

perjan6666 · Jul 17, 2012

i don't remember so i have to take a look.
i'm pretty chore that its 2 wires connected because it is a switch witch breaks one wire and the motor stops
i have easy access to 24v dc so i want to use it to control the circuit board.

maybe its necessary with a memory?

but i was thinking to have 4 micro switches 1 in each end to make speed go constantly up or down to make chore that the torque is between the outer switches,
and 2 switches in the middle to adjust the speed with timer and only little at the time to perfect the adjustments

alec_t · Jul 17, 2012

i'm pretty chore that its 2 wires connected because it is a switch witch breaks one wire and the motor stops

Are you saying the 10k pot also includes an on/off switch?

i have easy access to 24v dc so i want to use it to control the circuit board.

You first need to tell us what voltage is across the frequency-converter 10k pot.

maybe its necessary with a memory?

What will that be used for?

switches 1 in each end to make speed go constantly up or down to make sure that the torque is between the outer switches,

Not understood.

perjan6666 · Jul 17, 2012

the circuit board needs 4 inputs
memory to make it start at the same speed as when it was stopped (but not necessary if there is 4 switches)
there is a switch in the circuit of the pot, not included in the pot.
its just so the motor can be stopped when the the heat system get a error and shuts down,
the conveyor is going trough a 60 m long oven with 800 degrees Celsius inside.

read the first post and try to understand the problem and the way i want to solve it

perjan6666 · Jul 17, 2012

cal i measure the volt output from the frequency converter to the pot? i guess so i will do it to morrow

perjan6666 · Jul 17, 2012

a little drawing

here is a drawing to help explain

alec_t · Jul 18, 2012

The drawing is indeed helpful. Having seen it and been given the other info I don't think a simple circuit with a delay will give good enough safe control of what is clearly a large industrial conveyor belt with presumably variable loads on it. IMO you will need a sophisticated micro-controlled system with proportional/integral/derivative or similar complex functions, particularly to handle safety issues. That's way beyond my experience. Sorry I can't help further, but others on the forum may be able to. Good luck.

perjan6666 · Jul 18, 2012

i understand it is a large industrial production-line but it is the same load all the time and the speed is only changed 1 time a week by the operators, the speed is changed on the main engine.

safety is not a problem because i is fuses and also i will install safety switches to make the motor stop when something happens.

to day i was looking in to the wiring of the frequency converter and i discover that i was completely wrong about the pot.

there was 3 wires and i was trying to measure some voltage but i can not understand how to measure.
i stopped the motor and used ohm between the pot terminals and ground and it was no connection.

i also think it is 1k pot i have a picture of the pot.

perjan6666 · Jul 18, 2012

ok here is the user-manual on the inverter: https://www.electro-tech-online.com/custompdfs/2012/07/Mitsubishi-Freqrol-FR-S500-Manual.pdf

it is a Mitsubishi S500

it seems to be 5 volt dc in to the pot

here is the text in the user-manual: PAGE 11
Frequency
setting
potentiometer
1/2W1k
(*4)
*4 When the setting potentiometer is used frequently, use a 2W1kΩ potentiometer.

pot terminal 1 wired to 5 (Common)
pot terminal 2 wired to 2 DC 0 to 5V Selected DC 0 to 10V Selected
pot terminal 3 wired to 10 (+5V)

When using current input
Current input (-) terminal 5 (Common) on the inverter
4 to 20mADC (+) terminal 4 (4 to 20mADC) on the inverter

When using the current input as
the frequency setting signal, set
"4" in any of Pr. 60 to Pr. 63 (input
terminal function selection), assign
AU (current input selection) to any
of terminals RH, RM, RL and STR,
and turn on the AU signal.

from what i understand it will be more easy to use the the current input as the frequency setting signal

alec_t · Jul 18, 2012

That gives all the info we need about the pot and its use. As you say, it would probably be easier to use the 4-20mA loop for control instead. Again, sorry, I've no experience of using those in an industrial control system so others would be better qualified than me to advise you. I believe there are other members who have posted threads previously on control system problems.
What concerns me is that without knowing such things as motor powers, torques, conveyor loading, friction forces etc (which are all subject to change) it is difficult to design a circuit to vary the control current in a suitable way using a simple delay. Because of the large system inertia a simple control might lead to motor speed-hunting and destructive oscillation of the whole system. This is why complex PID controls are generally needed to prevent such a problem. So system safety is not just a matter of fitting a fuse

perjan6666 · Jul 18, 2012

ok but in this case it is enough with a delay in fine tuning to prevent the speed to adjust up and down all the time because the motor is going niche and steady and remember this control is only for the helping motors, and the main motor can drive the hole belt if i take off the chains on the help motors

but can u design a component list and wiring diagram for me so i can do some testing?
i want 4 on / off you decide the voltage

input 1 - as long as there is voltage in it will decrease the milliamp by 1 each second until the voltage disappears from the input
input 2 - as long as there is voltage in it will decrease the milliamp by 0,5 each (adjustable time delay 1-20 second) until the voltage disappears from the input
input 3 - as long as there is voltage in it will increase the milliamp by 0,5 each (adjustable time delay 1-20 second) until the voltage disappears from the input
input 4 - as long as there is voltage in it will increase the milliamp by 1 each second until the voltage disappears from the input

this inputs will not be trigged at the same time

alec_t · Jul 19, 2012

As I understand the manual, setting a speed using the REX, RH, RM, RL terminals will over-ride the 4-20mA control. Have you taken that into account?
I'll have a think about the current control you propose in post #12.

perjan6666 · Jul 19, 2012

yes these terminals are not connected to anything
it would be nice if you can design something like in post 12

ronv · Jul 19, 2012

Is the pot on the helper motor controller??

perjan6666 · Jul 19, 2012

no only wired to those 3 terminals

alec_t · Jul 19, 2012

A 0.5mA change in 20 secs implies a time constant of ~ 600 secs which would be very difficult to achieve reliably and consistently if an analogue method using resistors and a capacitor were to provide the delay you ask for. It would necessitate an electrolytic capacitor with attendant problems, because charging current for the cap would be comparable to the cap leakage current. Hence a digital solution would be obligatory IMO. Although a digital design could be implemented with many discrete logic and counter circuits it would be preferable to use just a micro-controller to handle the timing, and a D/A converter to provide drive for the controlled current current source. Do you have micro programming skills and facilities?

ronv · Jul 19, 2012

perjan6666 said:
no only wired to those 3 terminals

Click to expand...

What I meant was which motor does it make go faster and slower??

perjan6666 · Jul 19, 2012

alec_t said:
A 0.5mA change in 20 secs implies a time constant of ~ 600 secs which would be very difficult to achieve reliably and consistently if an analogue method using resistors and a capacitor were to provide the delay you ask for. It would necessitate an electrolytic capacitor with attendant problems, because charging current for the cap would be comparable to the cap leakage current. Hence a digital solution would be obligatory IMO. Although a digital design could be implemented with many discrete logic and counter circuits it would be preferable to use just a micro-controller to handle the timing, and a D/A converter to provide drive for the controlled current current source. Do you have micro programming skills and facilities?

i was thinking a 555 timer chip could maybe help

maybe i explained wrong, i meant that it will change the milliamp by 0,5 ant then Wait the time delay before repeat the progress as long as there is a voltage applied to the input

and i think it would be nice to have the opportunity to change how much the milliamp changes at the time also ex. from 0,1 ma to 3,0 ma

perjan6666 · Jul 19, 2012

ronv said:
perjan6666 said:

What I meant was which motor does it make go faster and slower??

Click to expand...

the pot is controlling frequency-inverter witch is connected to a 3-phase 400 volt motor, that have the purpes to help the main engine to move the conveyor

look at post 7 the help motor is the problem
look at previous post to understand how it works

motor moment project

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