How to simulate a power cut in circuits with CIs

[AferVentus]

Hi,

since the power source pin of CIs are implied as VCC, I cannot simulate a power cut that affect a circuit using CIs.

I mean, I'd like to simulate the behavior of a JK flip-flop CI, such as 4027, that has its power source cut off. But I'd need to do this without stopping the simulation (the rest of the circuit must keep working on).

For instance: I want to measure how long a electrolitic capacitor can keep the flip-flop CI on, until the power supply is reestablished.

It's possible to change the power supply (on or off) through a switch only in circuits composed by discrete components. If we use a CI, the power supply of the CI is implied and always on with no variation. But, in a real circuit, the power supply of a CI is the same of the entire circuit and is affected by the same variations.

I couldn't figure out how I can get control over the VCC in MultiSIM so I can simulate power cut including in CIs.

Thankyou,

[Mauro Vera]

Buenas tardes,

Por favor, más detalles sobre su aplicación y se puede conmutar el circuito. Gracias.

Atentamente,

[AferVentus]

The circuit detects when the battery voltage drops below 9V (the zener D1 and the transistor Q1 do the job).

Adjust the potentiometer R1 to do this. When it reaches 20%, the voltage on the zener drops below a value that makes the transistor Q1 stop conducting.

So, the JK flip-flop's outputs change their state, wich means, the other battery is selected as the power source.

Back the potentiometer to 0% (simulating you replaced the battery) and now adjust the potentiometer R6.

When it reaches 20%, the previous battery is again selected.

My question is about the flip-flop CI. When the changing of the power supply from a battery to another occurs, the MultiSIM doesn't show if the lack of power affects the CI.

So, I'm not able to determine if I have to use a electrolitic capacitor to maintain the CI with a minimal power as long as the circuit takes until the new battery is selected and the power is reestablished.

I know that when the shift occurs, the whole circuit has its power cut for a short time. Is it short enough so MultiSIM cannot detect it or is it short enough so it doesn't make difference on the circuit behavior?

Using the 74LS107D[74LS_IC] I can wire the VCC and GND pins, but using the 74LS107D[74LS] the power supply is implied and I don't have control of it.

But in both cases (both models) the lack of power seems not to make any difference.

Thankyou.

Stanley.

[Tayyab_R · Accepted solution]

Hi,

I was able to achieve the desired results. First thing you need to do is go to Simulate -> Mixed-Mode Simulation. Then select Use Real Pins(second radio button). Take a look at the attached circuit. I used a Piece_Wise voltage source and entered the voltage values for different times. You can do the same thing in your design and then like shown in the attached circuit, create an on-page connector and connect all the digital components to that so that they can use that voltage level.

Hope this helps.

[AferVentus]

Thankyou.