From the Junk Box:

[rattus]

Needed to find a buried solenoid in a lawn sprinkler system; didn't want to spend any money, so,

Wired a 6Vdc relay coil in series with the NC contacts to make a buzzer.

Connected the buzzer in series with a 6V lantern battery and the solenoid wire pair.

The buzzer generates a lot of radio noise, so I used an AM portable radio to follow the line until I found the solenoid. You can also find shorts this way.

If the line is open, you would connect the relay coil in parallel with the wire pair, but I have not checked this out.

The radio should be tuned away from station frequencies.

 

[cadpoint]

Needed to find a buried solenoid in a lawn sprinkler system; didn't want to spend any money, so,

Wired a 6Vdc relay coil in series with the NC contacts to make a buzzer.

Connected the buzzer in series with a 6V lantern battery and the solenoid wire pair.

The buzzer generates a lot of radio noise, so I used an AM portable radio to follow the line until I found the solenoid. You can also find shorts this way.

If the line is open, you would connect the relay coil in parallel with the wire pair, but I have not checked this out.

The radio should be tuned away from station frequencies.

Care to expand on any information on any of it ?
My first question is what if the solinod is bad, how could it hold any incoming voltage ?
Is it in fact, put'n a "scream" on the line, or an EMF(I know its DC)
thats your hearing ? Or is it the chatter/"noise" of the (test) relay coil that your seeking that produced cause its not to a complete curcuit thus your dig spot ? Why a NC contact, is that your safety feature ?

 

[rattus]

Care to expand on any information on any of it ?
My first question is what if the solinod is bad, how could it hold any incoming voltage ?
Is it in fact, put'n a "scream" on the line, or an EMF(I know its DC)
thats your hearing ? Or is it the chatter/"noise" of the (test) relay coil that your seeking that produced cause its not to a complete curcuit thus your dig spot ? Why a NC contact, is that your safety feature ?

If the solenoid coil is not open, RF currents circulate through both lines and these lines act as broadcast antennas.

Although the average current is DC, there are plenty of RF frequencies generated by the buzzer and that is what we hear on the radio. Similar to the RF noise generated by fluorescent lamps.

The NC contact is necessary for the relay to chatter. The relay pulls in, then immediately releases when the NC contact opens, then it repeats ad nauseum. Try it.

If the line is broken, or if the solenoid coil is open, we wire the relay coil across the solenoid wires. Again we have an antenna. Haven't tried this yet though.

There are many variations of this scheme which will work, for example you might use a 28Vac relay to eliminate the battery. Haven't tried this one either.