220V AC present/absent to TTL logic ?

[vlad777]

What is the best way to get
220V AC present/absent to TTL logic representation ?
(open collector, 10-15 mA)

I experimented with cny17-3 and I conclude it takes too much
input current (more then 6 mA) to saturate it's output transistor.
Too much input current means more power for resistors and
bigger cap.

Is there a better solution?

Thanks.

 

[Externet]

Optocoupler. I have done it with neon-to-phototransistor, convenient to have hysteresis/filtering to get rid of the 60 Hz if will drive logic.

 

[vlad777]

Is there an IC or you used discrete components?

 

[Externet]

I used a neon bulb superglued to a phototransistor inside black shrink tubing, sealed ends. Still works after 10+ years.

 

[vlad777]

I think I will use something like this.
SFH628A would have been better choice.
If a signal passes slow enough trough the middle
TTL logic will oscillate because it will amplifie the noise;
so schmitt trigger might have to be used.

 

[Externet]

Yes, that should work. I used neon because my AC was riding on top of 50V DC and I wanted to recognize the AC presence only.