Simulation Options for Control Circuits with Slave Relays

Thread Starter

F Leader

Joined Jul 9, 2020
1
Hi everyone

Does anyone have any suggestions for a way to simulate simple control circuits please, to ensure they work as expected, without having to physically wire them. I am an Electrical Engineer for a high speed door manufacturer, and I am responsible for designing the circuits for the control systems behind our doors.

Typical example of a circuit attached-
24Vdc supply, lots of inputs and outputs, the outputs being relays, often use slave relays, indicator lights, push buttons, etc.
Lots of logic that influences when the door opens, closes, locks, or when beacons / sounders / traffic lights are activated.
What would be the best software (preferably free) that could definitely simulate these circuits please?

I have tried multi sim, but found it quite complex and unsure if I was doing it correctly.

Thanks in advance!
Freya
 

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eetech00

Joined Jun 8, 2013
3,946
Hi everyone

Does anyone have any suggestions for a way to simulate simple control circuits please, to ensure they work as expected, without having to physically wire them. I am an Electrical Engineer for a high speed door manufacturer, and I am responsible for designing the circuits for the control systems behind our doors.

Typical example of a circuit attached-
24Vdc supply, lots of inputs and outputs, the outputs being relays, often use slave relays, indicator lights, push buttons, etc.
Lots of logic that influences when the door opens, closes, locks, or when beacons / sounders / traffic lights are activated.
What would be the best software (preferably free) that could definitely simulate these circuits please?

I have tried multi sim, but found it quite complex and unsure if I was doing it correctly.

Thanks in advance!
Freya
If you are looking for software that simulates electrical circuits and provides animation, sound effects, etc., then
LTspice, while free, is probably not a good choice for you. You might want to look at electrical simulation software like this:

https://www.cmhsoftware.com/constructor.html

Its not free, but its targeted at electrical circuits and moderately priced for what it provides.
 

crutschow

Joined Mar 14, 2008
34,420
If you want free, LTspice (which several on this forum can help you with) will readily simulate the circuit you posted, otherwise eetech00's suggestion may be better.
 

michael8

Joined Jan 11, 2015
414
I've simulated the operations of a clothes washer (maytag A610) in python. The program has the wiring
connections and simulates applying power. Things happen (simulated) like the timer, water fill, spin etc.
The code follows the power through the circuit and activates the devices when powered.

Not all that difficult.

I did it this way as the inputs are the cycle by cycle timer cam arrangement and the wiring diagram.
So neither of these are in the code other than as tables/data. This helps avoid errors or mismatches
between the real machine and the simulation.

PS: This washer has NO electronics, just electro-mechanical motors, switches, and solenoids.
 

LvW

Joined Jun 13, 2013
1,755
Hi everyone

Does anyone have any suggestions for a way to simulate simple control circuits please, to ensure they work as expected, without having to physically wire them.
There are some block-oriented simulation programs on the market - especially suited for control applications.
One of the most versatile programs is VISSIM (from visual solutions).
As an alternative, the simulation package PSIM (from powersim) also allows control loops based on blocks (with transfer functions) instead of real parts ans amplifiers,
 

MisterBill2

Joined Jan 23, 2018
18,477
Prior to creating a simulation, an understanding of what is happening and what actions cause what results is mandatory. Otherwise it is all random guesses. I have written many control programs in ladder logic, which has real advantage of showing cause and effect, action and result.
For a line follower, the sensor bits should be: just a bit off the line, half off the line, and almost all off the line, This requires state awareness to know the difference between fully off the line and completely on the line. It also requires understanding the rate of correction. But that scheme can provide proportional plus derivative control. Integral control is used to compensate for measuring delays and so it may not be applicable to a fuzzy logic control system.

And really, fuzzy logic is only a half-way approximation of analog logic, which would have been a much better name for the method, but probably not provided as much profit for those marketing it.
 
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ericgibbs

Joined Jan 29, 2010
18,848
Does anyone have any suggestions for a way to simulate simple control circuits please, to ensure they work as expected, without having to physically wire them
Bill,
If you read the TS post, you will see that he is asking for suggestions for a suitable simulator.

Not your negative bias regarding simulators

E
 

MisterBill2

Joined Jan 23, 2018
18,477
I believe that Automation Direct offers a program that can emulate a PLC operation without having the PLC involved. And since relay logic is all digital logic anyway, logic emulators are able to duplicate it easily.
BUT the exact words are "a way to simulate."
That has been done with paper and pencil for many years, it is called a "timing chart".
It is usually done with grid type chart paper, although ordinary lined paper can work. Each element has a line, that shows graphically the state of that element, either 1 or 0(= on or off)
Starting at the left side, the first change is entered, followed by adding the results of that first change. Next column shows the results of the changes in the first column. So it does need to have the state analyzed after each element change. But it certainly does work It does require having an organized circuit schematic that shows all of the elements, and all of the inputs and outputs.

It might be that a simple emulator could produce the "truth Table for a relay control system that would be adequate.
 

MaxHeadRoom

Joined Jul 18, 2013
28,684
Typical example of a circuit attached-
24Vdc supply, lots of inputs and outputs, the outputs being relays, often use slave relays, indicator lights, push buttons, etc.
Lots of logic that influences when the door opens, closes, locks, or when beacons / sounders / traffic lights are activated.
What would be the best software (preferably free) that could definitely simulate these circuits please?

I have tried multi sim, but found it quite complex and unsure if I was doing it correctly.

Thanks in advance!
Freya
What you are describing is a system that begs the implementation of a PLC..!!
And would have thought the answer to this is to use a PLC for the whole intended project and its end result?
And if so, then the PLC itself does all the simulation and debugging during the planning and programming stage.
 

MisterBill2

Joined Jan 23, 2018
18,477
Of course, the relay control circuit must be drawn in a manner that allows following the functionality without struggle. THAT requires a bit of learning. Following a relay circuit via a wiring diagram, even with just two or three relays, can be a serious challenge, as I have seen in this very forum in the past.
The very best simulation is to show the relay circuit in the ladder diagram listing format, which does require that every element be identified.
If the terminal identification is added during creation of the ladder diagram, then it will provide a self-checking build document for those who build the physical system, if it is not a logic listing for a PLC.

"Ladder Drawings" predate the first PLC by at least 30 years, probably much more.
 

MisterBill2

Joined Jan 23, 2018
18,477
"Fuzzy Logic" as applied to improving digital systems, is adding the equivalent of 3 or 4 bit A/D converters to the digital logic systems. It should have been obvious to those folks tasked with creating control schemes, but evidently many skilled at digital logic were not aware that the real world is all analog, including all of the non-linear stuff.
So I have no criticism of Fuzzy Logic, except the promoting of it as some wonderful new creation.
 

MaxHeadRoom

Joined Jul 18, 2013
28,684
Hi everyone
Typical example of a circuit attached-
24Vdc supply, lots of inputs and outputs, the outputs being relays, often use slave relays, indicator lights, push buttons, etc.
Lots of logic that influences when the door opens, closes, locks, or when beacons / sounders / traffic lights are activated.
" lots of inputs and outputs, the outputs being relays, often use slave relays, indicator lights, push buttons"
"Lots of logic"
There seems to be 'Lots' missing from the DWG?
As mentioned, relay logic for substantial systems was phased out with the advent of the PLC creation by Dick Morley in '68 .
If in N.A., I suggest you get a copy of NFPA79, also if wishing to get into PLC, there is a publication by John Ridley "Programming Logic Controllers" , it is based around the Mitsubishi PLC, which I primarily use, but covers basics applicable to most.
For smaller systems, there is the Smart Relay, which has many features of its bigger brother, the PLC.
In the NFPA79 there is examples of ladder logic etc and the way the Boolean functions are connected in a 'ladder' fashion where the logic progresses from the left side of the 'Ladder' to the resultant output on the right.
The beauty of these (PLC) systems is, is that all the logic status can be monitored in real time, on a PC screen.
If you are an Electrical Engineer, as you say, it is almost imperative that you have a good working knowledge of implementing Electrical diagrams in ladder format, including PLC awareness.
 
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MisterBill2

Joined Jan 23, 2018
18,477
By the way, that attachment to post #1 is at least partly a wiring diagram, NOT a circuit schematic, which will make it obvious if the assembly will function as desired. So it seems that actually, an accurate circuit schematic drawing IS A GOOD SIMULATION of a circuit. And if that drawing is done in a logical manner it shows clearly if and how the circuit will operate.
That will apply also to a circuit schematic that includes "Fuzzy Logic".
There are available lists of rules that will assist those not aware about how to produce a circuit schematic drawing that is easy to follow and proceeds in a logical order.
 

MaxHeadRoom

Joined Jul 18, 2013
28,684
Here is a publication by Schneider on electrical circuits, Although many show something which is now considered bad practice, the placing of the O/L on the RH side of the relay coil.
Particularly if the RH rail is a grounded neutral.
It should be placed to the LH side of the Coil.
1703650457890.png
 

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MisterBill2

Joined Jan 23, 2018
18,477
Given that in most motor starters the overload contacts are closely wired to the contactor, and sometimes monitored by external means, there is a reason for that convention. IN ADDITION, locating the connection on that side reduces the possibility of unknowing persons bypassing them by making it less convenient.
BUT, relative to the discussion at hand, the ladder listing makes the operation of the circuit completely obvious to allwho understand the meanings of the symbols. If terminal identifications were added the same drawing would serve for those who would actually be wiring the assembly.
 

MaxHeadRoom

Joined Jul 18, 2013
28,684
To add a rider to my previous post #18. the DWG is for the hardwired version, in the case of a PLC, the N/C O/L contact would be wired externally on the hot (live) side of the coil and now that contactor O/L's have both N/C & N/O contacts, the N/O would be used for advising the PLC of the O/L Status.
NFPA79 also now show the recommended method of placing the N/C O/L on the "live" side of the contactor coil..
 
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