![schematic](https://i.stack.imgur.com/eubw5.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2feubw5.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)

As you can see in the above circuit, I have converted AC to DC.

The transformer used in the above circuit is : If I apply 230V across the Primary, then I get 12V across the secondary coil of transformer.

Then I convert it to DC using 4 Diodes and a capacitor.

This DC voltage is applied to the coil of Relay.

This circuit works as expected.

**Problem:**

When I decrease the voltage on Primary coil of transformer.

Suppose I apply 200V to the Primary coil of transformer then also the chances are that Relay coil gets energized.

**What I want:**

If there is 12V or higher applied at the Red box in the diagram, then only the coil of relay should get energized else I should get 0V across the two terminals of relay coil.

I asked one of my friend about this problem. He said I should use a Zener diode in this circuit to achieve what I want. But I don't know where do I place the Zener?

Can anybody give me a suggestion?