Switching 24vac

[alp]

Hello.

I would like to interupt a circuit several times a second. The circuit
carries 24vac to a solenoid circuit under ground somewhere.

What I want to do is open and close this circuit several times a second so I
can actuate and un-actuate the solenoid, causing it to buzz.

I need to find this solenoid and have been unable to do so. I hope the
buzzing can help me home in on it.

What I am thinking of is perhaps something run off a 555 to trigger some
sort of electronic switch for the 24vac.

Any ideas on chips for this purpose?

Thanks,

Alp

 

[Phil Allison]

"alp"

I would like to interupt a circuit several times a second. The circuit
carries 24vac to a solenoid circuit under ground somewhere.

What I want to do is open and close this circuit several times a second so
I
can actuate and un-actuate the solenoid, causing it to buzz.

I need to find this solenoid and have been unable to do so. I hope the
buzzing can help me home in on it.

** Why not feed the output of an audio amplifier into to 24 volt AC line ?

Some screaming heavy metal music should provoke the solenoid into a bit of
"grunging" noise so you can locate it with you ear to the ground.



........ Phil

 

[ehsjr]

Hello.

I would like to interupt a circuit several times a second. The circuit
carries 24vac to a solenoid circuit under ground somewhere.

What I want to do is open and close this circuit several times a second so I
can actuate and un-actuate the solenoid, causing it to buzz.

I need to find this solenoid and have been unable to do so. I hope the
buzzing can help me home in on it.

What I am thinking of is perhaps something run off a 555 to trigger some
sort of electronic switch for the 24vac.

Any ideas on chips for this purpose?

Thanks,

Alp

For this application, just use a 555 to operate
a relay at something between 3 and 20 Hertz. The
relay can interrupt the 24 vac to the solenoid.
You should add a snubber across the relay points,
made from a 100 ohm resistor in series with a .1 uf
250V capacitor. Make sure the relay contact
rating exceeds the current that the solenoid draws.

Ed

 

[Jamie]

Hello.

I would like to interupt a circuit several times a second. The circuit
carries 24vac to a solenoid circuit under ground somewhere.

What I want to do is open and close this circuit several times a second so I
can actuate and un-actuate the solenoid, causing it to buzz.

I need to find this solenoid and have been unable to do so. I hope the
buzzing can help me home in on it.

What I am thinking of is perhaps something run off a 555 to trigger some
sort of electronic switch for the 24vac.

Any ideas on chips for this purpose?

Thanks,

Alp

they have wire tracers for that.

 

[alp]

I didn't think a relay could operate at the frequency needed (to buzz a
solenoid). That is why I asked about an electronic switch.
However, your explanation seems solid (apart from my doubt about the max
frequency the relay contacts can operate at).
I will consider it. Thanks.

Alp

 

[alp]

DJ Delorie wrote:

A PC parallel port, an optotriac, and an alternistor should be enough
for such a temporary circuit.

I use 24vac switching in my furnace controller boards:
http://www.delorie.com/house/furnace/

Now this is an interesting idea.
I wonder if I can fashion something without a PC parallel port. (555 would
be fine).
I'll have to look up more on alternistors and triacs I think.
Thank you!

Alp

 

[alp]

they have wire tracers for that.

Yes they do. I do not wish to buy one.

Alp

 

[Jamie]

Yes they do. I do not wish to buy one.

Alp

hmm.
How about using your friends metal detector for a
day?

 

[amdx]

For this application, just use a 555 to operate
Hi Alp,
Here's a completely different technique you could try, I've used it very
successfully
to locate and follow buried coax for my antennas. I saw this hint somewhere
on the net.
Take a small portable radio tuned to station, lay the radio down on a table
and rotate
the radio around, you will find a spot where the signal strength diminishes.
Actually
there are two nulls in the signal, 180 degrees apart. If you don't find a
good null try
this outside on the ground or try a different station.
Now with the radio rotated for the null, move it across the ground where
you think
the cable is, when you are above the cable it will transmit a signal and you
will hear
the radio signal. Follow the cable until the signal is no longer there, and
you should
be near the valve. This works great on antenna coax cables, you might have
to disconnect
the wires at the power source and add 10 or 20 ft of wire just to get a
little more signal
on the buried wire.
Give it a try,
Mike

 

[John Popelish]

Hi Alp,
Here's a completely different technique you could try, I've used it very
successfully
to locate and follow buried coax for my antennas. I saw this hint somewhere
on the net.
Take a small portable radio tuned to station, lay the radio down on a table
and rotate
the radio around, you will find a spot where the signal strength diminishes.
Actually
there are two nulls in the signal, 180 degrees apart. If you don't find a
good null try
this outside on the ground or try a different station.
Now with the radio rotated for the null, move it across the ground where
you think
the cable is, when you are above the cable it will transmit a signal and you
will hear
the radio signal. Follow the cable until the signal is no longer there, and
you should
be near the valve. This works great on antenna coax cables, you might have
to disconnect
the wires at the power source and add 10 or 20 ft of wire just to get a
little more signal
on the buried wire.
Give it a try,
Mike

I haven't used that method, but I have used an AM radio to
follow buried wiring and pipes.

I connect a battery to a small DC relay, with the coil in
series with a normally closed contact, so that the relay
buzzes the way a doorbell works. I connect one side of the
battery to a ground rod and the coil end that connects to
the contact to the conductor to be followed. The coil
generates a noisy broad band pulse splatters all over the AM
band. I tune the radio between stations at the low end of
the band (where ground penetration is maximal, but antenna
efficiency for the buried conductor in minimized, so only
the near field is significant. I can follow the buried
conductor by swinging the radio back and forth across the
conductor, centering the peak of the buzz in the swing.

I was able to help a friend find the route of a buried
plastic sewage pipe this way, by flushing one end of a
flexible wire, attached to a fishing bobber, down the
toilet, to act as the radiating conductor.

 

[John Fields]

I haven't used that method, but I have used an AM radio to
follow buried wiring and pipes.

I connect a battery to a small DC relay, with the coil in
series with a normally closed contact, so that the relay
buzzes the way a doorbell works. I connect one side of the
battery to a ground rod and the coil end that connects to
the contact to the conductor to be followed. The coil
generates a noisy broad band pulse splatters all over the AM
band. I tune the radio between stations at the low end of
the band (where ground penetration is maximal, but antenna
efficiency for the buried conductor in minimized, so only
the near field is significant. I can follow the buried
conductor by swinging the radio back and forth across the
conductor, centering the peak of the buzz in the swing.

I was able to help a friend find the route of a buried
plastic sewage pipe this way, by flushing one end of a
flexible wire, attached to a fishing bobber, down the
toilet, to act as the radiating conductor.

 

[DJ Delorie]

I'll have to look up more on alternistors and triacs I think.

I mention alternistors and not triacs because alternistors are
designed for inductive loads, and your solenoid is one. But you can
use a regular optotriac (MOC30xx family) to trigger them.

 

[ehsjr]

I didn't think a relay could operate at the frequency needed (to buzz a
solenoid). That is why I asked about an electronic switch.
However, your explanation seems solid (apart from my doubt about the max
frequency the relay contacts can operate at).
I will consider it. Thanks.

Alp

A typical general purpose relay will transfer in roughly
10 ms, so to go from de-energized to energized and back
to de-energized, figure 20 ms. Then add a "fudge factor"
of 150% (because we don't have the specs of the actual relay)
to get 50 ms. That translates to 20 cycles per second -
a typical relay can do at least that.

Ed

 

[Rich Grise]

I would like to interupt a circuit several times a second. The circuit
carries 24vac to a solenoid circuit under ground somewhere.

What I want to do is open and close this circuit several times a second so
I can actuate and un-actuate the solenoid, causing it to buzz.

So, how did this turn out?

Thanks,
Rich

 

[neon]

first of all how do you know that the wires are still connected to the relay? check resistance lately??????
second any relay can and will cycle on-off if the dc power is connected through the contacts a capacitor can change the buzzer frrequency. then run the same dc trough the relay contacts to your relay power if the wires are good the relay still alive then yes you may locate it chasing the sound. drive a spike into the earth and listen. no timer LM555 REQUIRED JUST ANOTHER DPDT RELAY. GOT THAT? SIMPLE.