Oscillating 14 segment display on falling edge in multisim

[totalbite]

Hello all,

I dont understand the behaviour of the 14 segment display in multisim. When I connect  a switch (which is connected to a 5V power supply) directly to the pins of the seg display, this works fine. When I put a logical gatter between switch and seg display it works correctly on rising edge. But when I generate a falling edge (by opening the switch) the corresponding leds of the connected pins start to oscillate (going on and of again and again) until I close the switch again. Can somebody explain to me why this is so and how I can get rid of that?

Thanks & Greets,

Ranschid

[yyao]

Hello Ranschid,

The flickering behaviour has to do with the way Multisim is simulating your circuit. As you may know from circuit theory, the solutions to most circuits include time based derivatives and integrals. Multisim can perform definite integrals using two methods: gear or trapezoidal. The trapezoidal method is faster and is usually fine for analog circuits, however, sometimes, it leads to oscillatory behaviour. Because of its speed advantage, Multisim perfers the trapezoidal method by default.

You can change the integration method to gear for your situation by doing the following:

1 - Click Simulate>>Interactive Simulation Settings

2 - Click on the Analysis Options tab

3 - Under SPICE Options, select Use Custom Settings

4 - Click Customize

5 - Click on the Transient tab

6 - Check the box beside Integration method

7 - Select gear from the drop down menu beside the integration method

8 - Click OK

9 - Click OK

Thats a very good question you asked. Hope this works for you.