readVoltage() reading only 0 or 5

Question

Gun Min Song 2018-11-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/428568-readvoltage-reading-only-0-or-5

评论： Álvaro Aparicio Serna 2020-9-25

From an Arduino Mega I am outputting 0,1,2,3,4 volts using writePWMVoltage function (at D13), then I connected D13 to A0 for readVoltage. In theory, I am supposed to get 0,1,2,3,4V from A0, but I am only getting values 0 or 5 from A0. I already checked D13 is outputting correct values by measuring with DMM.

Am I wiring something wrong? Why is this happening? Any help is appreciated :)

2 个评论
显示无隐藏无

Gun Min Song 2018-11-7

在 MATLAB Online 中打开

This is the code I used for this experiment ----------------------------------------------

clear
clc
a = arduino
for i=0:4
    writePWMVoltage(a,'D13',i)
    voltage(i+1) = readVoltage(a,'A0')
    pause
end
writePWMVoltage(a,'D13',0)
voltage(6) = readVoltage(a,'A0')

Walter Roberson 2018-11-8

https://www.mathworks.com/help/supportpkg/arduinoio/ref/writepwmdutycycle.html

Try setting the duty cycle higher in case it is returning to base before you can read it.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Rohan Kale 2020-2-14

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/428568-readvoltage-reading-only-0-or-5#answer_415537

In my understanding you are trying to read the DC voltages from the PWM waveforms generated on D13. Your code sequence seems to be alright. However, the hardware setup is where the problem is originating. In theory, the DC i.e. mean voltage, can be changed by changing the PWM duty cycle. I think the readVoltage API is just picking up the instances where the waveform is either a LOW or a HIGH, that's why you are reading either 0V or 5V. In order to read DC voltages correctly from the waveform, you may want to insert an RC filter between the PWM and analog pins. The RC filter will essentially increase the decay time as the capacitor would now discharge slowly. Try varying time constant of the circuit, may be keep it as 0.1 seconds. This should probably solve your issue.