Lost ground alarm?

Thread Starter

My Tech Guy

Joined Feb 18, 2009
31
How hard would it be to make a simple circuit that when the ground was removed, then a buzzer would go off?

I'm simply trying to monitor a lightning rod connection.

I'm guessing I would need a relay of some sort for this correct?
 

MaxHeadRoom

Joined Jul 18, 2013
19,387
What you could do is feed a relay coil with a low isolated voltage to one side of the coil, connect the other coil terminal to the lightening rod above the point you like to monitor and connect the other side of the supply to the ground rod connection or to a separate ground rod driven close.
If the relay opens it triggers the NC contact and supplys the alarm.
Max.
 

Thread Starter

My Tech Guy

Joined Feb 18, 2009
31
Thanks for responding MaxHeadRom. I was hoping to use a common 9 volt battery to power the buzzer. To increase the batteries life I was hoping that the battery would not be connected until the ground was removed. Is that how your circuit works above?
 

SamR

Joined Mar 19, 2019
1,471
Max's idea is a basic powered loop using the ground connection for holding a normally closed contact open and not a bad idea. There are several ground loss detectors on the market for monitoring AC system ground loss which is a safety issue. Monitoring an unpowered ground is a bit unique and will somehow require power to signal a change of status. Interesting and intriguing problem. My question would be survivability when the static collector grounds a discharge and the ground loss detector is exposed to the discharge?
 

Thread Starter

My Tech Guy

Joined Feb 18, 2009
31
Monitoring an unpowered ground is a bit unique and will somehow require power to signal a change of status. Interesting and intriguing problem.
At first I thought that maybe using two relays would solve this, but I'm not so sure and don't see a way around having the voltage supplied all the time. How long do you think a 9 volt battery would last being connected to the coil all the time?

My question would be survivability when the static collector grounds a discharge and the ground loss detector is exposed to the discharge?
That's a good question which I will test later. I'm mainly concerned to just have some sort of a working circuit for now.
 

Berzerker

Joined Jul 29, 2018
549
wouldn't the system monitoring the rod need a ground to work?
OH! No, No please don't say earth ground will work ....This is not code.
Brzrkr
 

SamR

Joined Mar 19, 2019
1,471
I'm not the battery guy around here but a simple DC circuit using a transistor to switch power to a relay would not draw much at all. Powering a relay coil on for extended periods or even a solid-state relay might be a problem for a small battery. It kinda goes against KISS to add another layer but for a longterm battery powered circuit it may be needed.
 

Berzerker

Joined Jul 29, 2018
549
Now I'm only guessing but if you hook a monitor up to a system that let's you know it's lighting in a storm it would be going off every few seconds. How can a ground be lost or absent? what for a few millseconds?
Brzrkr
 

Thread Starter

My Tech Guy

Joined Feb 18, 2009
31
I'm only guessing but if you hook a monitor up to a system that let's you know it's lighting in a storm it would be going off every few seconds.
The circuit I'm looking for has nothing to do with lightning. While I am using a lightning rod for ground, I am simply looking for a simple way to monitor the continuity between the rod, and the other end of the wire connected to the rod. If there is a break in that wire, the buzzer goes off.

I was trying to keep the thread title simple, but it probably should have the word 'continuity' somewhere in there ;)
 

SamR

Joined Mar 19, 2019
1,471
Most of those that I saw are industrial quality OSHA or MSHA required safety devices and not cheap but they should give you some ideas. Since they are monitoring panel ground there is lots of 120VAC available to power them.
 

MisterBill2

Joined Jan 23, 2018
4,469
I just now came across this thread, and I see lots of answers that do not seem to be related to your requirement, as I see it.
It seems that you are wanting a system to verify that the cable grounding your lightning protection devices is still adequately connected to the ground rod installed for that purpose, and that it has not much to do relative to any ground connection of your electrical power system.
Unfortunately battery power will not last for this application because it does require a current flowing into the ground system to verify that it is still connected.
So now I am going to make a presumption that you also want to verify that the wire to the ground rod is intact, which is very reasonable. A system to do this will need a connection to the lightning protection grounding cable at the start of the section that you want to monitor, ( point #1), and also a connection to another ground, such as your electrical system ground point, (point #2), which might be the water supply line, or a metallic well casing. A plastic line will not work. You will also need a low voltage transformer, possibly a doorbell transformer, possibly even the existing one, and a low voltage incandescent light, and an AC powered electronic buzzer. The electronic buzzer will be connected between these two points. Also connected between the same two points will be the low voltage secondary of the transformer in series with the light. As long as the grounds are both grounded the light will illuminate and the buzzer will be silent, but if either ground becomes disconnected then the light will go out, or at least go dim, and the electronic buzzer will sound.
The circuit works by passing a current from the transformer between the two grounds, with the light serving to limit the current. But if either ground connection is lost then the voltage between the two grounds will activate the electronic buzzer.
 

marcf

Joined Dec 29, 2014
257
"I am simply looking for a simple way to monitor the continuity between the rod, and the other end of the wire connected to the rod"

Why not use two wires with each end connected to different points on the rod. The two wires at the other end could be used to monitor for a break in the circuit.
 

MaxHeadRoom

Joined Jul 18, 2013
19,387
"

Why not use two wires with each end connected to different points on the rod. The two wires at the other end could be used to monitor for a break in the circuit.
That is essentially what I suggested, just that one end is at the grounded point.
@My Tech Guy What ever system you come up with it is virtually going to consume current to monitor the status.
You could obtain a very sensitive, low current coil relay, there are some that have a DIP type footprint that are low current.
I don't think you would have to worry about electrolysis with a DC current that small.
Max.
 
Last edited:
Top