Question For Community - 7-segment Equivalent Circuit Model.

293

03:44:51

As can be attested by my previous two circuits, the 7-segment display is not merely a light or even an LED in EveryCircuit.  There are other components involved inside that can sometimes make it behave in an unanticipated way.  Sometimes, an equivalent circuit can make the operation of a complex component easier to understand, and it can help when interfacing the component to surrounding circuitry.

The top circuit is the 7-segment display with a test input voltage source to act as a reference. The voltage and current are measured with the orange waveform and the blue waveform. 

Below is my attempt at an equivalent circuit model for one 7-segment input pin.  The voltage and current are monitored by the green and red waveforms.  For the two circuits to be equivalent, the behaviors should be the same, and the currents and voltages should match.  Green should match Blue, and Red should match Orange.

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This is where I could use some input from you.  How do you think I did?  Are there any areas you see that are not working the same?  Please comment below with your thoughts... 
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This is not intended to be a real-life approximation of a 7-segment display but rather an equivalent EC model.

My previous two circuits I alluded to for those interested:
7-segment Power Bank https://everycircuit.com/circuit/5861787383365632
7-segment Oscillator https://everycircuit.com/circuit/4620067509370880

published 2 years ago

jason9

2 years ago

A voltage sweep verifies that the two seem to behave completely identically.

592azy2circuitdude

2 years ago

Good to hear from you, Jason. Thanks for checking over my equivalent circuit. I'm not sure what a "voltage sweep" is. Is it a ramp voltage, like a sawtooth wave?

jason9

2 years ago

Yeah. I just applied a sawtooth and used the XY mode on the scope. The XY mode isn’t even necessary for the purpose of comparison, but it does gives a nice visualization of the voltage/current curve.

592azy2circuitdude

2 years ago

I just tried out the XY plot, and I like the way it shows the signals, too. Thinking about voltage sweeps made me think a frequency sweep on a Bode Plot would be a good test. I tried it, but I couldn't get it to work well since I didn't know how to measure the current magnitude.

jason9

2 years ago

You can measure current on the bode plot by using a current to voltage converter and measuring the voltage. A little ugly but gets the job done and doesn’t alter the operation of the circuit.

592azy2circuitdude

2 years ago

Good suggestion. I tried it out, and it worked great. Thanks a lot👍

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