The Relay in the Lumped Components section has threshold voltage and hysteresis voltage as parameters. I am not familiar with what those terms mean in the context of relays. I am familiar with the terminology usually used in datasheets such as Operate (aka Pull-in/Pick-up/Set) Voltage and Release (aka Drop-out/Reset) Voltage.
I thought that perhaps the threshold voltage would be the Drop-out voltage, and the hysteresis voltage would be the difference between Pull-in and Drop-out voltages. But, this does not appear to be the case.
In a simulation, it appears that the two voltages, threshold and hysteresis, are merely summed with the result being both the Pull-in and Drop-out voltage of the relay. For example, a relay with a threshold of 3V & a hysteris of 7V, in a sweep simulation of type List (2;3;4;9;10;13;14;10;9 voltage at DC source), the relay is energized only above 10V. At any voltage below 10V, the relay is de-energized.
So, I must ask, what is the meaning of threshold voltage and hysteresis voltage?
Last edit: T. Lee Davidson 2018-11-17
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From the relay component source code von = vt + vh and voff = vt - vh, where vt is the threshold and vh is the hysteresis. So vt would be the average of the Pull-in and Drop-out voltages and vh would be half of the difference between the Drop-out and Pull-in voltages.
These definitions are normally used for (Schmitt trigger) comparators but vh is usually just von - voff there.
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I did not see any definition of behavior, hence the reason I had to ask. For future reference, where might I find the particular source code of which you spoke?
P.S. I don't know why I didn't receive notification of your response, and I see no Notification options in Account Settings. :-S
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The Qucs source code is organized in several different directories; in particular the simulator (qucsator) is in its own directory, qucs-core/ . As you saw, the GUI code act only as an interface between the component instances in the schematic and the simulator, so it knows only about the components properties but not about their behavior. The behavior is defined by the simulator code and the relais model source code is in https://sourceforge.net/p/qucs/git/ci/master/tree/qucs-core/src/components/relais.cpp
Regarding the results you see they appear not correct because the simulator is not doing what you think it should be doing :) . In your schematic you have a DC and a sweep simulation: what a sweep simulation does is simply to run the main simulation specified there (DC1 in this case) multiple times, with a different parameter value for each simulation. The main point is that every simulation in a sweep is independent so it does not know about any previous results. For each parameter value a new simulations starts from the same initial conditions. So when the simulation with vSource=8.9 is run, it starts from the default condition, i.e. relay is open and since 8.9 V are below the voltage needed to close it when it is open the relay stays open.
What you need to do to see the relay hysteresis is a time domain simulation, which has a notion of "history" and know about the past states of the circuit.
Enclosed you'll find a test circuit which generates a triangular wave that goes from 0 to 10 V and shows the relay contact status over time; here the relay behaves as expected since the relay state at the previous time points is taken into account to compute the new state.
I really appreciate your clarification of the behavior of the sweep simulation (very helpful), and, especially, the time you took to create an example illustrating additional concepts :-)
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The Relay in the Lumped Components section has threshold voltage and hysteresis voltage as parameters. I am not familiar with what those terms mean in the context of relays. I am familiar with the terminology usually used in datasheets such as Operate (aka Pull-in/Pick-up/Set) Voltage and Release (aka Drop-out/Reset) Voltage.
I thought that perhaps the threshold voltage would be the Drop-out voltage, and the hysteresis voltage would be the difference between Pull-in and Drop-out voltages. But, this does not appear to be the case.
In a simulation, it appears that the two voltages, threshold and hysteresis, are merely summed with the result being both the Pull-in and Drop-out voltage of the relay. For example, a relay with a threshold of 3V & a hysteris of 7V, in a sweep simulation of type List (2;3;4;9;10;13;14;10;9 voltage at DC source), the relay is energized only above 10V. At any voltage below 10V, the relay is de-energized.
So, I must ask, what is the meaning of threshold voltage and hysteresis voltage?
Last edit: T. Lee Davidson 2018-11-17
From the relay component source code
von = vt + vhandvoff = vt - vh, wherevtis the threshold andvhis the hysteresis. Sovtwould be the average of the Pull-in and Drop-out voltages andvhwould be half of the difference between the Drop-out and Pull-in voltages.These definitions are normally used for (Schmitt trigger) comparators but
vhis usually justvon - voffthere.Thank you Claudio. That explains it very well.
I had previously looked at relais.cpp (and relais.h) in https://sourceforge.net/p/qucs/git/ci/master/tree/qucs/qucs/components/ . It appears to be merely a declaration of the objects properties.
I did not see any definition of behavior, hence the reason I had to ask. For future reference, where might I find the particular source code of which you spoke?
P.S. I don't know why I didn't receive notification of your response, and I see no Notification options in Account Settings. :-S
Further, according to what you stated, with a Vt of 6V and a Vh of 3V, the relay should pull-in at 9V and drop out at 3V.
It does not. It does pull in at 9V but then drops out at 8.9V.
The Qucs source code is organized in several different directories; in particular the simulator (qucsator) is in its own directory, qucs-core/ . As you saw, the GUI code act only as an interface between the component instances in the schematic and the simulator, so it knows only about the components properties but not about their behavior. The behavior is defined by the simulator code and the relais model source code is in https://sourceforge.net/p/qucs/git/ci/master/tree/qucs-core/src/components/relais.cpp
Regarding the results you see they appear not correct because the simulator is not doing what you think it should be doing :) . In your schematic you have a DC and a sweep simulation: what a sweep simulation does is simply to run the main simulation specified there (DC1 in this case) multiple times, with a different parameter value for each simulation. The main point is that every simulation in a sweep is independent so it does not know about any previous results. For each parameter value a new simulations starts from the same initial conditions. So when the simulation with vSource=8.9 is run, it starts from the default condition, i.e. relay is open and since 8.9 V are below the voltage needed to close it when it is open the relay stays open.
What you need to do to see the relay hysteresis is a time domain simulation, which has a notion of "history" and know about the past states of the circuit.
Enclosed you'll find a test circuit which generates a triangular wave that goes from 0 to 10 V and shows the relay contact status over time; here the relay behaves as expected since the relay state at the previous time points is taken into account to compute the new state.
Great information, Claudio. Thank you!
I really appreciate your clarification of the behavior of the sweep simulation (very helpful), and, especially, the time you took to create an example illustrating additional concepts :-)