pwm to analog

[maor]

Hello,
I have pwm signal of max 5v and min of 0v. i want to use opto coupler to change it to analog or digital signal of 0-5v, is it possible?

Thank you,

 

[Harald Kapp]

An optocoupler doesn't change a digital signal to an analog signal. You need to low-pass filter the pwm to remove the high frequency components. What remains is the DC component which is proportiional to the duty cycle and the amplitude of the pwm.

 

[maor]

1) so what happen if the input of the optocoupler is pwm? the output will be pwm or the average of the pwm?
2) what happen if the input of the optocoupler is a sine wave?

Thank you

 

[Harald Kapp]

1) so what happen if the input of the optocoupler is pwm? The output will be pwm or the average of the pwm?

PWM

2) what happen if the input of the optocoupler is a sine wave?

something resembling a very distorted sine wave. Optocouplers are - with exceptins - not made for transmitting analog signal, mostly digital ones.

Details vary with type of optocoupler and the exact circuitry used.

 

[maor]

and if i have input signal of 3v dc and ripple of 0.025v, the output would be 3v dc and much more ripple?

Thank you

 

[Harald Kapp]

and if i have input signal of 3v dc and ripple of 0.025v, the output would be 3v dc and much more ripple?

Not necessarily. A digital optocoupler is normally operated with the receiving transistor in saturation. It therefore will be saturated evn if the input current varies slightly. This will change if the circuit is designed such that the output is not saturated.

Look up some optocoupler theory to understand the behavior of optocoupler.

 

[maor]

And there is such thing analog optocouplers? if i let them sine wave the output will be sine wave?

Thank you

 

[(*steve*)]

There are some very expensive analog optocouplers and you can also couple a LED to a fast LDR to create something which works acceptably in some applications.

 

[Harald Kapp]

And there is such thing analog optocouplers?

Watch this thread.

 

[Colin Mitchell]

Why do you want to use an opto-coupler?