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MSP430F167: 230V A.C. mains detection with MSP430F167 gets on RESET or not responding while switching

Ramesh Polasa
Prodigy 70 points
Part Number: MSP430F167
Other Parts Discussed in Thread: TCA6424A, TIDM-THDREADING

Hi,

My application is to detect the AC voltage presence using Continuous high or low signal.

(I got the same issue with MSP430F167 and TCA6424A IO extender)

I am using a Non-Isolated power supply with 120mV Vp-p as supply.

circuit is as shown below where I need GPIO continuous Hi or Low

With this when voltage detected it is not going to zero instead it is some where around 0.6-1.2v

And some times there is a noise on IO which is Reaching Vp-p as much as 32V as shown below

I Tried Below circuits , with TVS

   

The 34v noise clamped and Iam only getting Ripple of 0.4-0.6v at AC Presence

when I used Schottky arrangement of GPIO As shown below 34v noise clamped but ripple was 0.8-1.2v 

now my question is which arrangement is better for my GPIO stability?

TVS of Schottky configuration? because rise time of noise is lessthan 10nS. even TVS is giving better performance Iam not sure will it sustain those type of continuous noise!

and My MSP430F167 is stucking / not responding when I get this noise. but with TVS/ schottky arrangement its not happening but when The GPIO state is above

1v instead of ground Its false triggering and some times stucking.

is there any way I can make this low level to 0V or less than 200mV.

  • 0
    TI__Mastermind 49692 points

    Hi Ramesh,

    This is an interesting implementation. You mentioned that you're not using an isolated power supply, so I'm assuming you're connecting the MSP430F167's GND to Neutral. If so, I'm not sure why you're isolating the phase-to-neutral input using an optoisolator. Typically, for a non-isolated power supply, the communication interface (e.g. UART TX/RX pins) between the MSP430 and the host is isolated.

    I don't see how the high voltage noise would be coming through the optoisolator, so it may be related to your power supply and transients from opening/closing the switch. You could try disconnecting your power supply and using a battery to power the MSP430. If the noise goes away, then I think there's a lack of protection on or around your power supply implementation.

    My recommendation would be to implement something similar to the Zero crossing detection using comparator circuit. Remove the optoisolator and just use a resistor divider to reduce the Phase voltage with respect to Neutral. Then, you could add a zener diode to remove the negative portion of the AC signal and apply that signal to the MSP430F167's Comparator_A module. You could probably add a capacitor in parallel with the zener diode to smooth out the signal. Then, you could define the Comparator_A thresholds to easily trigger an interrupt when the AC input turns off.

    To protect the Comparator_A inputs, I would recommend that you follow the guidelines for the voltage AFEs in some of our metering reference designs (e.g. TIDM-THDREADING).

    Regards,

    James

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