mains voltage detector for UPS/Mains transfer

[sam100]

mains voltage detector

Hi,
I'm looking for a simple circuit to detect the mains voltage level with nearly no time response for a unit that transfers the output between mains & UPS
thanks

 

[Tahmid]

Hi,

Try this:

When mains is present, a 0 signal is received and when no mains is present a 1 signal is received. Use this signal in your inverter circuit for transferring between outputs.

Hope this helps.
Tahmid.

 

[sam100]

Hi Tahmid
Thanks for quick answer, the problem with this circuit is that:
I can't control the input voltage level (very low voltage would operate the LED & activate the output

 

[karesz]

Hi sam100,
Sorry, I can not understand your problem; With the serial resistor you can set the minimal mainsvoltage to control the couppler - make it active...
K.

Added after 3 minutes:

What do you wish exactly pls?
Only an indicator- can be simple, or an trigger signal for your UPS starting, it must be precise, also can not be simple-primitive...

 

[Tahmid]

Hi,
In that case, try this:

Change the value of the zener accordingly. You'd be best off using a 2W zener. Less would work though.

Hope this helps.
Tahmid.

 

[betwixt]

I would stick to the original circuit but add two zener diodes back to back in series with the incoming AC. Using a resistor alone will not give consistent results, the detection voltage will depend on temperature and component tolerances.

Use the property of Zeners that they conduct like normal diodes when forward biased to cause a predictable voltage drop. For example, if your supply was 240V and you use two 100V Zeners, the opto-coupler would work normally down to 140V before starting to switch off.

Brian.

 

[karesz]

Dr OM,
Good Idea!
73 de Karesz

 

[rajudp]

in UPS we have to change to UPS mode above 170V
normally i use transformer with micro controller to detect voltage level, for non isolated one you can use resister divider network

 

[sahu]

can any one provied sqer. wave inv with charging besad on pic 16f 72\676. code + ckt diagram.

 

[shazan]

I would stick to the original circuit but add two zener diodes back to back in series with the incoming AC. Using a resistor alone will not give consistent results, the detection voltage will depend on temperature and component tolerances.

Use the property of Zeners that they conduct like normal diodes when forward biased to cause a predictable voltage drop. For example, if your supply was 240V and you use two 100V Zeners, the opto-coupler would work normally down to 140V before starting to switch off.

Brian.

like this?

This will make a signal every half cycle as soon as the mains voltage drops below the zener voltage? How do we distinguish between an actual failure and a half cycle interruption? I need to wait for some time? Am I missing something?