Current flow detector for remote water pump.

1 view
Skip to first unread message

Steve W.

unread,
Aug 22, 2007, 10:49:19 PM8/22/07
to
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 W.

Bob AZ

unread,
Aug 23, 2007, 12:42:42 AM8/23/07
to

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

Arfa Daily

unread,
Aug 23, 2007, 4:34:34 AM8/23/07
to

"Bob AZ" <rwats...@aol.com> wrote in message
news:1187844162.8...@r23g2000prd.googlegroups.com...
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

Ross Herbert

unread,
Aug 23, 2007, 5:44:08 AM8/23/07
to
On Wed, 22 Aug 2007 22:49:19 -0400, "Steve W." <ya...@yahoo.com>
wrote:

This Electronic Design article describes a fully blow pump monitor
system
http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=1682

You don't need much more than the pump interface part of the circuit
with a lamp driver added.

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

HapticZ

unread,
Aug 24, 2007, 8:16:08 AM8/24/07
to
buy a baby monitoring device pair. cheap $14 wally mart

should be good for 200-300 feet straight line distance

hook the transmitter ac adapter to the pump, when the pump turns on, it
powers the sound transmitter.

leave the receiver plugged in, when pump is on you will get clear sound of
actual pumpperfromance.

also, if the pump loses it's prime, the pitch should change and you may
react.

then
"Steve W." <ya...@yahoo.com> wrote in message news:faisjd$mj3$1...@aioe.org...

vey

unread,
Aug 24, 2007, 1:42:34 PM8/24/07
to

Maybe I am stupid, but couldn't you just wire a 120 lamp cord and bulb
in parallel with the pump? You would do this at the switch. When the
pressure switch closed, then the pump and the bulb would come on.

Or you could wire in after the controller box, if you have one.

But make sure that this really is a 120 pump. Most are 240 and then you
would wire one hot to one side of the bulb and neutral to the other side
of the bulb.

vey

unread,
Aug 24, 2007, 4:40:36 PM8/24/07
to

Oops, sorry.

Steve W.

unread,
Aug 24, 2007, 5:47:36 PM8/24/07
to

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.
--
Steve W.

vey

unread,
Aug 24, 2007, 6:37:14 PM8/24/07
to

Could you put an ammeter inline with the circuit? It would take a
sizeable shunt. There is a place in my city that sells used and surplus
electronics. They have AC ammeters for $15(?).

Arfa Daily

unread,
Aug 24, 2007, 8:31:30 PM8/24/07
to

"Steve W." <ya...@yahoo.com> wrote in message news:fanjlj$b93$1...@aioe.org...

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
elsewhere in the thread.

Arfa


DaveM

unread,
Aug 24, 2007, 9:29:48 PM8/24/07
to
"Steve W." <ya...@yahoo.com> wrote in message news:fanjlj$b93$1...@aioe.org...

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
address)

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


DaveM

unread,
Aug 24, 2007, 9:44:48 PM8/24/07
to
"Steve W." <ya...@yahoo.com> wrote in message news:fanjlj$b93$1...@aioe.org...

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

http://web3.automationdirect.com/adc/Overview/Catalog/Sensors_-z-_Encoders/Current_Sensing_Switches/Multi-Range_AC_Current_Operated_Switches_with_Time_Delay

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!!!

Arfa Daily

unread,
Aug 25, 2007, 9:02:31 AM8/25/07
to

"DaveM" <mason...@comcast99.net> wrote in message
news:Qeadne1TC5IMFFLb...@comcast.com...

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


Message has been deleted

Peter K

unread,
Aug 25, 2007, 3:33:34 PM8/25/07
to
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
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:HLVzi.21023$mZ5....@newsfe6-win.ntli.net...

James Sweet

unread,
Aug 25, 2007, 7:29:08 PM8/25/07
to
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.


Bill Jeffrey

unread,
Aug 28, 2007, 2:09:46 PM8/28/07
to
> 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

DaveM

unread,
Aug 28, 2007, 4:42:58 PM8/28/07
to
"Bill Jeffrey" <wjef...@TAKE-THIS-OUTalum.mit.edu> wrote in message
news:46d464f8$0$6433$4c36...@roadrunner.com...

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
load(s).
The transistor circuitry can easily be replaced with an opamp if you're more
comfortable with those.
The Smart Strip is rated at 15A.

Reply all
Reply to author
Forward
0 new messages