detect zero current of motor ac in order to switch the output of microcotroller pic16

[mmmary]

I am doing a project controlling an asynchronous motor 230V / 6Amax with triac which is controlled by a microtrolleur, now I want to add to the circuit a part to detect the zero-current in motor side caused by the presence of Limit switch and inject the result to the microcontroller, can I use the gold shunt resistors or it is mandatory to use a hall effect sensor witch i find them more expensive . i don' have much idea in this type of circuit can someone help please thanks

 

[barry]

Not quite sure what you're saying. Are you saying you want to detect when the switch to the motor is open? What do you mean by "gold" resistors? Are you proposing putting a resistor in series with the motor, and detecting the voltage across that?

The resistor approach would work fine, but a simpler solution might be to get a double-pole limit switch and use the second pole to indicate when the switch is activated.

 

[KlausST]

Hi,

In an AC system with 50/60Hz mains frequency the current will be zero 100/120 times per second..
Therefore i assume you need to rectify and filter the signal.

An important thing to know is whether you need isolation or not.

***
On first sight i assume
* a current transformer
* rectifier
* voltage limiter
* RC low pass filter
* comparator or schmitt trigger
Could do the job

There are many other ways...

Klaus