Hi:

Thanks for the responses. The load is a very quiet water pump. It draws
between 5 and 40 amps depending on water load. We need to know not just when
the on/off breaker is activated, but when the pump is actually on and
drawing battery load. The circuit will drive an indicator lamp via a relay.

I have some small reed relays, do you think a coil of the pump's feed wire
will trip it to make contact? That would be easy.

Thanks


"jon doe" wrote in message
...
Hi:
Looking for a simple circuit idea that will tell us when a 12V DC load is
activated. This is a critical load so we don't want to do anything that
will
make it unreliable. The circuit just has to activate a tiny relay when the
load is going. Any ideas?
Thanks

On Sun, 5 Mar 2006 14:07:57 -0500, "jon doe" wrote:

Hi:

Thanks for the responses. The load is a very quiet water pump. It draws
between 5 and 40 amps depending on water load. We need to know not just when
the on/off breaker is activated, but when the pump is actually on and
drawing battery load. The circuit will drive an indicator lamp via a relay.

I have some small reed relays, do you think a coil of the pump's feed wire
will trip it to make contact? That would be easy.

Thanks


"jon doe" wrote in message
Just look at the specs on reed relay elements. if trigger level is 100
Ampere turns then 20 turns around element will give you what you want.
Simple option for encapsulated relays is to break open case and cut
off existing fine wire coil. You now have a former to wind your heavy
gauge wire.. Otherwise wind your wire around a screwdriver of similar
diameter to the element then slide element in. I suggest that you do
not wind directly on element - they are fragile!
I have done just what you are requiring with a water pump. the reed
switches on a battery clock. Runtime of clock tells me the state of my
water tank. Its a very cheap but working option.

Richard

Nb "Pound Eater" Parkend G+S
Please remove your hat when replying

How about using an AMMETER ?
http://en.wikipedia.org/wiki/Ammeter

Yes, I know the other suggestions above are actually home-made
ammeters. Don't blast me.

I know there are small aircraft ammeters with built in alarms, which
you
might find beneficial... not sure what marine offering exist.

On 6 Mar 2006 07:22:48 -0800, "
wrote:

How about using an AMMETER ?
http://en.wikipedia.org/wiki/Ammeter

For a simple indicator, they take up too much panel space.

"Wayne.B" wrote in message
...
On 6 Mar 2006 07:22:48 -0800, "
wrote:

How about using an AMMETER ?
http://en.wikipedia.org/wiki/Ammeter

For a simple indicator, they take up too much panel space.

put a light bulb, of low wattage and appropriate voltage across the
contacts. Bulb lights when pump is off. Or put a relay coil (NC) in
place of the bulb and use to light bulb when contacts close. A small
current would flow through the pump all the time but it shouldn't do
anything.