A question in a competition that just ended in Hangzhou

gmchen

A question in a competition that just ended in Hangzhou [Copy link]

2022 TI Cup Analog Electronic System Design Invitational Competition Topic X Lissajous Figure Demonstration Device

1. Mission

Design and implement a Lissajous figure demonstration device, as shown in the figure. Input a sinusoidal signal as the x-axis signal, with a peak-to-peak value of 2V and a frequency of 1.5kHz~2kHz; convert the input sinusoidal signal by amplitude and frequency to generate a y-axis signal; and display the corresponding Lissajous figure on the device display.

II. Requirements

(1) The frequency multiples of the y-axis and x-axis signals are programmable from 1 to 5 times, with a step of 1; the absolute value of the frequency error is not greater than 100 Hz.

(2) The y-axis signal peak-to-peak value is programmable at 1V, 2V, or 3V, and the absolute value of the amplitude error is no more than 0.1V.

(3) The y-axis sinusoidal signal can be converted into a corresponding triangular wave signal.

(4) The device can measure and display the initial phase difference between the y-axis and x-axis signals (see φ in the figure), and the absolute value of the measurement error is no more than 5°.

(5) The Lissajous figure is displayed on the device display.

(6) Others.

3. Description

(1) The "signal conversion" part of the device is not allowed to use digital signal processing methods (which will be checked during testing). Suggestion: frequency control can be achieved using a phase-locked loop + counter; amplitude control can use digital potentiometers, analog switches, field-effect transistor variable resistors, etc. to control the op amp gain.

(2) The device must provide a unique y signal output measurement interface.

gmchen

Notes

Competition time limit: from 8 am on the first day to 8 am on the second day

List of required components, including:

Op amp, LM324, 2 pcs

Comparator, LM339, 1 pc

Analog switch, CD4052, CD4053, 1 each

Phase-locked loop, CD4046, 1 piece

Counter, 74HC161, 1

Gate circuit, 74HC00, 74HC08, 74HC32, 74HC20, 1 each

NMOS transistor, IRF540, 1 pc

Digital potentiometer, TPL0401A, 1 piece

gmchen

The question itself is not difficult, but it is still challenging to complete it within 24 hours. In particular, some of the requirements in the question require a good understanding of phase-locked loops to perform well.

I will post the topic in this thread first, and then write an analysis article when I have time after some time.

okhxyyo

It sounds interesting. Waiting for the author's analysis.

soso

Wow it's just in time :)

吾妻思萌

I remember seeing Lissajous figures on an oscilloscope, magical transformations

fetchstar

The idea is very clear, but the key to analog circuits is debugging. It should be relatively easy to just give a solution in principle. If you really want to see the graphics, it will be a bit troublesome.

lkh747566933

The idea is very clear, but the key to analog circuits is debugging. It should be relatively easy to just give a solution in principle. If you really want to see the graphics, it will be a bit troublesome.