Trying to build an earth leakage device that will alarm at 30V+

[challie2]

Hi all

as mentioned in the subject what im trying to build, is an electronics device that detects earth faults. Essentially trying to make my own contactless tester. And also the ability to attach a test lead with a crocodile clip, to detect earth faults, essentially a 2 in 1 job. When everything is normal and no earth fault detected, there is a 2 contact relay with 1 NC and 1 NO. When the coil of the relay is energised an LED is illuminated. When a 30V+ fault is detected, it de energises the relay the 1st LED extinguishes, and then another LED with a Buzzer are powered.  There should also be a test button to test the circuit works, and a reset button, if the fault is still there after the reset button is pressed, it instantly alarms again. Attached is an image of what I have made so far. I am really struggling to get it working, and could really do with some help I am beginner with Electronics.

Thanks

[moffy]

So are you trying to build basically an insulation tester for earths?

[wasedadoc]

Earth leakage testers usually monitor current, not voltage.

[David Hess]

Check out the service manual for the Tektronix A6901 Ground Isolation Monitor which does what you are describing.  It has full schematics.

https://w140.com/tekwiki/wiki/A6901

[challie2]

I suppose of sorts yes. Thanks for the reply

[challie2]

Kind of what I’m trying to build. Thanks

[Terry Bites]

What you actually want to detect is still very unclear. It doesn't seem like you want to measure earth leakage currents.

I think its an earthing failure detector. So, say when loss of ground at the low side of your circuit casues it to climbs to 30V.
When circuit ground gets 30V higher than PE maybe?

In which case a latching voltage detector is what you need and it appears your schematic is intended to do just that.
Here's an idea for a cheap detector made from the bits you might already have laying about the bench.