recognize 220 V AC signal and produce a logic signal ???

[Myself]

pc817 zerocrossing

Dear all,

I need a schematic diagram showing an input module to recognize 220 V AC signal and producing a logic signal in advance.


I know there are some designs in PLC books but I need a tested and sure working circuit.

Thank you very much for your help in advance.

Myself

 

[nicleo]

I need a schematic diagram showing an input module to recognize 220 V AC signal and producing a logic signal in advance.

Sorry to ask as I don't really to get your question...

What do you mean 'recognize 220 V AC signal'?
Does the 'logic signal' work as trigger signal? Or a continous logic pulses?

 

[Myself]

What I would like to do is similar to that of an AC input module for a PLC.

When a 220VAC signal is applied to this circuit it will provide a 5V DC output and this signal will be available as long as the applied 220VAC signal is present.

But I need a working circuit.

Thanks to anyone trying to help me.

 

[nicleo]

When a 220VAC signal is applied to this circuit it will provide a 5V DC output and this signal will be available as long as the applied 220VAC signal is present.

How much power required by the 5V DC output? Or, it's just a 'signal' (low power) that works as an indicator?

 

[IanP]

Get youself an opto-isolator.
On its primary you have a diode. Connect another diod in parallel with this one but anode-to-cathode (reverse polarity protection).
Calculate a value of a resistor that will be connected in series with these two diodes (take current between 5-10mA @ 220V*1.4).
Secondary of this opto-isolator will be a transistor: connect its emiter to GND and collector to +5V through 10k resistor.
Signal at the collector is your usable signal (50Hz pulses, 0-5V).

 

[rauol]

U can use a capacitor instead of resistor for limiting current in optoisolator. with capacitor power loss can be avoided.

 

[Johnson]

Actually you need a zero crossing circuit, the schemit trigger is another choice

 

[VVV]

I would go with the optocoupler solution, followed by either a gate and a filter or by a retriggerable monostable to produce a clean HI or LOW from those 50/60Hz pulses.

Although less efficient, I would choose the resistor in series with the opto (don't forget the diode in antiparallel with the LED). The capacitor can cause high inrush currents that can damage the LED. It all depends on when the AC line is applied; so, if it's applied right at its peak, chances are the LED will get damaged.

 

[irfansyah]

I agree with the optocoupler solution, i even used it and it works nicely in my design. I use a cheap PC817 optocoupler from Sharp for this. The input for the PC817 comes from a step-down transformator, and the input current is limited by a suitable R (current value = 20 mA, roughly).

How about using physical AC relays? I think thay may work also

 

[aym_qunibi]

i have built a 3phase failure detect device using drop resistors then i have usedan optoisolator, the output signal is fed to a lowpass filter which is fed to the microcontroller on a digital i/o pin.

the customer need the smaller as i can so i have used a resistors but i realy recommend you to use a step-down transformer.

 

[antedeluvian]

Depending on your configuration, you could simply use a relay with a 220VAC coil.

It may be advisable to have this as an external device (to your pcb) and to use gold plated contacts if you are running low currents. Also remember the delay before the contacts de-activate, and the possibilty of contact bounce (more of a problem when the contacts make than when they break).