# Current flow detector for remote water pump.

S

#### Steve W.

Jan 1, 1970
0
Looking for a way to activate a small lamp to show when a remote mounted
water pump is running. I know I have seen the method before but my dusty
brain cannot seem to find it. The pump is a 120volt unit mounted in a
remote pump house out of visual range or I would wire a light across the
pressure switch. I was thinking of something like an inductive coil
around the hot lead feeding a circuit that would power the light. No
problem working on the panel end. Ideas?

B

#### Bob AZ

Jan 1, 1970
0
Looking for a way to activate a small lamp to show when a remote mounted
water pump is running. I know I have seen the method before but my dusty
brain cannot seem to find it. The pump is a 120volt unit mounted in a
remote pump house out of visual range or I would wire a light across the
pressure switch. I was thinking of something like an inductive coil
around the hot lead feeding a circuit that would power the light. No
problem working on the panel end. Ideas?

Steve

Perhaps a current meter is called for. And I am sure there are current
sensing relays that would light a bulb. Also a pair of wires from the
remote pump house would be a way. I am sure there are other solutions.

Bob AZ

A

#### Arfa Daily

Jan 1, 1970
0
Bob AZ said:
Steve

Perhaps a current meter is called for. And I am sure there are current
sensing relays that would light a bulb. Also a pair of wires from the
remote pump house would be a way. I am sure there are other solutions.

Bob AZ
I have seen it done using a small current transformer made by feeding the
cable through a ferrite ring, and winding a few extra turns of thin wire on
there, which is then fed to a little opamp circuit, the output of which, you
can do what you like with - feed a relay, switch a bulb, switch a little
license-exempt transmitter, and so on. I'm pretty sure that Elektor magazine
did a circuit like this as a project not so long back. You could try
searching the archive on their website at www.elektor-electronics.com

Also, I think that you can get ready made units for control of computer
peripherals. You just plug your computer in through it, and when it detects
that the primary load - your computer - is drawing current, it switches
power to auxilliary devices like your printer. Subbing the pump for the
computer, and using one of its switched aux outputs to drive a relay or
whatever, should work. Also, simplest way perhaps, connect a wall wart power
supply across the pump feed. Then when the pump comes on, you will have a
low voltage of any value you choose, available to do what you like with. If
you can't get wires easily to where you need to know that the pump is
running, then a wireless link is probably going to be best. You can get all
sorts of ready built modules for transmit and receive now. The ranges, and
directivity, can be extended considerably, by adding home brew external
antennas.

Arfa

R

#### Ross Herbert

Jan 1, 1970
0
Looking for a way to activate a small lamp to show when a remote mounted
water pump is running. I know I have seen the method before but my dusty
brain cannot seem to find it. The pump is a 120volt unit mounted in a
remote pump house out of visual range or I would wire a light across the
pressure switch. I was thinking of something like an inductive coil
around the hot lead feeding a circuit that would power the light. No
problem working on the panel end. Ideas?

This Electronic Design article describes a fully blow pump monitor
system

You don't need much more than the pump interface part of the circuit

HCPL3700 data sheet
http://www.datasheets.org.uk/datasheet.php?article=1608384

H

Jan 1, 1970
0

A

#### Arfa Daily

Jan 1, 1970
0
Steve W. said:
Not stupid and I could do that BUT The pump itself is almost 200 feet away
down over a bank in a pump house. I am hoping to be able to connect
something inside the house on the feed to the pump to tell me when it is
operating, rather than burying a lot more wire.

If I had a transformer here that could handle the 15 amps I would hook one
side of it into the hot side of the feed and use it to power a light since
current/voltage would only be flowing when the pump was on but that would
be a good sized transformer. I think my current course of action will be
to wrap a section of the hot side through a toroidal core with a larger
section of magnet wire and see what I get voltage wise. Kind of a
crossbreed current transformer.

You're fairly unlikely to get enough to be able to do much with on it's own,
but if you slung it across the inputs of an opamp, and smoothed the result
at the output, you'd have enough to drive a small relay to switch a low
power transmitter - like a WalMart baby alarm, as someone suggested

Arfa

D

#### DaveM

Jan 1, 1970
0
Steve W. said:
Not stupid and I could do that BUT The pump itself is almost 200 feet away
down over a bank in a pump house. I am hoping to be able to connect something
inside the house on the feed to the pump to tell me when it is operating,
rather than burying a lot more wire.

If I had a transformer here that could handle the 15 amps I would hook one
side of it into the hot side of the feed and use it to power a light since
current/voltage would only be flowing when the pump was on but that would be a
good sized transformer. I think my current course of action will be to wrap a
section of the hot side through a toroidal core with a larger section of
magnet wire and see what I get voltage wise. Kind of a crossbreed current
transformer.

Don't know what your budget for this contraption is, but I think what you're
looking for is a current-operated switch, such as these:
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

D

#### DaveM

Jan 1, 1970
0
Steve W. said:
Not stupid and I could do that BUT The pump itself is almost 200 feet away
down over a bank in a pump house. I am hoping to be able to connect something
inside the house on the feed to the pump to tell me when it is operating,
rather than burying a lot more wire.

If I had a transformer here that could handle the 15 amps I would hook one
side of it into the hot side of the feed and use it to power a light since
current/voltage would only be flowing when the pump was on but that would be a
good sized transformer. I think my current course of action will be to wrap a
section of the hot side through a toroidal core with a larger section of
magnet wire and see what I get voltage wise. Kind of a crossbreed current
transformer.

Don't know what your budget for this contraption is, but I think what you're
looking for is a current-operated switch, such as these:
http://www.dynacononline.com/ct805.htm

Find more manufacturers, distributors and prices by Googling for "current
operated switch".

An alternative would be a Smart Strip power strip
http://catalog.bitsltd.us/power_strips/. This is a power strip that has a
number of outlets, just like the cheap "surge suppressor" strips, the difference
being that there is one outlet that is used to control all the other outlets.
When the device that is plugged into the control outlet is on (drawing current),
the other outlets are switched on. These are usually used to control computer
systems, home theater systems, etc, where a number of devices need to be turned
on at the same time. I have one of these strips in my home and two more in my
shop. Great devices.
You could run the pump through the smart switch, and then plug a small lamp or
other device into one of the controlled outlets for a visual or audible
indication that the pump is drawing current.

Cheers!!!
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

A

#### Arfa Daily

Jan 1, 1970
0
DaveM said:
Don't know what your budget for this contraption is, but I think what
you're
looking for is a current-operated switch, such as these:
http://www.dynacononline.com/ct805.htm

Find more manufacturers, distributors and prices by Googling for "current
operated switch".

An alternative would be a Smart Strip power strip
http://catalog.bitsltd.us/power_strips/. This is a power strip that has a
number of outlets, just like the cheap "surge suppressor" strips, the
difference being that there is one outlet that is used to control all the
other outlets. When the device that is plugged into the control outlet is
on (drawing current), the other outlets are switched on. These are
usually used to control computer systems, home theater systems, etc, where
a number of devices need to be turned on at the same time. I have one of
these strips in my home and two more in my shop. Great devices.
You could run the pump through the smart switch, and then plug a small
lamp or other device into one of the controlled outlets for a visual or
audible indication that the pump is drawing current.

Cheers!!!

Good steer on the links Dave. That's exactly the piece of kit I was telling
him to look for back up the top.

Arfa

M

#### Meat Plow

Jan 1, 1970
0
Good steer on the links Dave. That's exactly the piece of kit I was telling
him to look for back up the top.

Good idea as long as the startup amps drawn by the pump don't exceed the
rating of the strip's breaker.

P

#### Peter K

Jan 1, 1970
0
Hi

I know this will not operate a lightbulb, but :

Get a Panelmount ammeter with Current Transformer (CT).
Hook the CT up to the ammeter, and pass one of the phase wires going to the
pump assy through the CT.

Ammeter will show you when the pump runs.

P

J

#### James Sweet

Jan 1, 1970
0
You can get current relays from HVAC surplus type places, they're just a
relay wound with a heavy wire designed to carry the load current, the relay
closes when current flows through the coil. I think I paid \$2 for the one I
bought, you could probably rewind the stator of an AC relay with some #12
enameled wire in a pinch too.

B

#### Bill Jeffrey

Jan 1, 1970
0
An alternative would be a Smart Strip power strip
http://catalog.bitsltd.us/power_strips/. This is a power strip that has a
number of outlets, just like the cheap "surge suppressor" strips, the difference
being that there is one outlet that is used to control all the other outlets.
When the device that is plugged into the control outlet is on (drawing current),
the other outlets are switched on. These are usually used to control computer
systems, home theater systems, etc, where a number of devices need to be turned
on at the same time. I have one of these strips in my home and two more in my
shop. Great devices.

If I am not mistaken, the sensor in a smart strip is nothing but a pair
of rectifier diodes connected in anti-parallel. You put the pair in
series with the line. When the load (the pump in this case) draws
current, the voltage across the diodes is a near square wave with an
amplitude of 1.4 volts peak-to-peak. You can use this voltage to pull in
a small relay, which in turn lights your indicator light - or whatever.

Obviously, the diodes have to be hefty enough to withstand the pump's
starting current. And the relay's coil, which is connected to the line
at all times, must be well isolated from the relay frame, from ground,
from its own contacts, etc. But none of this is hard.

Bill

D

#### DaveM

Jan 1, 1970
0
Bill Jeffrey said:
If I am not mistaken, the sensor in a smart strip is nothing but a pair of
rectifier diodes connected in anti-parallel. You put the pair in series with
the line. When the load (the pump in this case) draws current, the voltage
across the diodes is a near square wave with an amplitude of 1.4 volts
peak-to-peak. You can use this voltage to pull in a small relay, which in turn
lights your indicator light - or whatever.

Obviously, the diodes have to be hefty enough to withstand the pump's starting
current. And the relay's coil, which is connected to the line at all times,
must be well isolated from the relay frame, from ground, from its own
contacts, etc. But none of this is hard.

Bill

You are mistaken. The Smart Strip that I mentioned uses a current transformer
to sense current. The CT feeds a transistor that switches a relay when current
in the control receptacle is sensed.
However, CTs aren't hard to find, and are pretty cheap. The circuitry behind
the CT is fairly trivial as well... just connect a burden resistor across the CT
secondary, rectify and filter, then feed the resulting voltage to the base of a
transistor. The transistor drives the relay coil, which switches power to the
The transistor circuitry can easily be replaced with an opamp if you're more
comfortable with those.
The Smart Strip is rated at 15A.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

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