Brown out protection

[.]

Hi
I have a 12V relay that is being fed from the mains by a capacitor power
supply, through a bridge and a 12Vcrowbar zener.

If I get a brown out my relay chatters. Is there a simple single component
that will act like a DS1810 Econo Reset, except at about 10V instead of
4.5V? That is, hold its output voltage to zero until the supply returns to
an acceptable level.

I don't have much room and hope someone can suggest a single component
solution.

Any suggestions appreciated

Kez

 

"." <ppppp@wh.com.au> wrote:

Hi
I have a 12V relay that is being fed from the mains by a capacitor power
supply, through a bridge and a 12Vcrowbar zener.

If I get a brown out my relay chatters. Is there a simple single component
that will act like a DS1810 Econo Reset, except at about 10V instead of
4.5V? That is, hold its output voltage to zero until the supply returns
to
an acceptable level.

I don't have much room and hope someone can suggest a single component
solution.

Any suggestions appreciated

Kez

Hi Kez

If my understanding of the circuit is correct; capacitors are being used
instead of a transformer to drop the voltage for this relay.
There is no filter capacitor mentioned either.
If this is so, the voltage across the relay coil will be a pulsed DC.
This complicates things somewhat.
If this relay has a spare/isolated set of contacts maybe the following might
work.
Install a resistor in series with the relay coil so that the relay only engages
at or near normal mains voltage.
When the relay engages use the spare contacts to short out this resistor.
This will provide some hysterisis and reduce or eliminate the chattering.

Note: The capacitors do not properly isolate the high voltage mains, do not
work on this circuit while it's powered up!

Regards

Strill


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