AC-line monitoring without VCC

[qashq11]

Hi all,

We are looking for technique or device that can detect ac line with some logic-out voltage without the need of VCC digital voltage.

Googling it, I found the MID400 device of fairchild, but it need VCC as output voltage stage, and we looking for device that can operate from the same AC line in its input stage.

Suggestion will be helpful.

Thanks.

 

[Golden Electronics]

logic output voltage range ?

 

[qashq11]

between 5 and 12 volts.

Its suppose to operate a relay coil which need that "logic" voltage.

 

[Venkadesh_M]

why shdnt you just use small trasnformer and rectifier for relay??

 

[qashq11]

because the leakage current from the transformer.
it's for medical application.

 

[Golden Electronics]

Use resistor network is okay

 

[Venkadesh_M]

when using to optocoupler you will totaly isolat the AC then how it will give 5V when AC available without Vcc?

 

[Golden Electronics]

Can u explain ur application so that we can support properly.

 

[qashq11]

OK...

We have an isolating transformer such that its primary consist with 2 seperate coils, and so its secondary.
The system is powered with 220VAC, and the input can be 110VAC or 220VAC.
If the input is 110VAC than the pins should connect parrallelly. If 220VAC it should connect serially.

I am looking for technique (ac relays, triacs and so) such that it can detect the presence of the 220VAC and switch the coils pins properly.

Any ideas?

 

[FvM]

This won't work with a single relays. The switches must be operated break-before-make with sufficient deadtime to avoid shorting of the mains voltage by contact arcing. I can't imagine a simple implementation.

 

[qashq11]

How is it relate?

I planned to use 2 relays anyway.

 

[Venkadesh_M]

If R1 and R2 are as it is both coils will be in parallel, If the 230 Vis detected and the contacts changed It will make a series connection...