Load In Use Indicator Circuit Needed
 

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

Load In Use Indicator Circuit Needed
 

What kind of load? How is it activated?

Simply, an opamp connected across a current sensing shunt in a voltage
comparator configuration will work.

Putting the relay coil in line with the sensed loads feed 'might' also
work, depends on the loads etc.

Ian

Load In Use Indicator Circuit Needed
 

On Sat, 4 Mar 2006 23:35:48 -0500, "jon doe" wrote:

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

Take a reed relay element and take a number of turns of your load wire
around it! If the required switched load is too great for the reed
then slave it through a larger relay!
Cannot get much simpler than that!

Richard

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

Load In Use Indicator Circuit Needed
 

What are you willing to define as "evidence" that the load is activited?
A specific level of current drawn by the load? Presence of 12 VDC at the
load? Switch to the load in the "on" position? Presence of the load's
output (e.g., sound, heat, light, motion, water flow, etc.)? The load's
output is usually, but not always, present when the load is drawing
current of course. An electronic navigation device could draw current
forever and yet not work at all.

The most obvious solution (power the relay with the same switch you use
for the load) is probably the most reliable method if all you want to do
is verify that power to the load is switched on.

Other seem to have figured out what you are seeking from your post, but
I can't see the info there.

Chuck





Electricky Dicky wrote:
On Sat, 4 Mar 2006 23:35:48 -0500, "jon doe" wrote:


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


Take a reed relay element and take a number of turns of your load wire
around it! If the required switched load is too great for the reed
then slave it through a larger relay!
Cannot get much simpler than that!

Richard

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

Load In Use Indicator Circuit Needed
 

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

Load In Use Indicator Circuit Needed
 

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

Load In Use Indicator Circuit Needed
 

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

Load In Use Indicator Circuit Needed
 

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.

Load In Use Indicator Circuit Needed
 

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.

Load In Use Indicator Circuit Needed
 

"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.

Load In Use Indicator Circuit Needed
 

Hello:
Thanks to all for your thoughts.
I ended up doing the reed relay trick. I used 12awg wire, 4 wraps around the
body of the relay. It flickers just a bit, then locks on and gets my
indicator lamp running. I didn't want to use less then 12awg wire as I was
afraid of getting in trouble (the original cable is 10 awg). I could only
get 4 wraps, so I went with that......


"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

Load In Use Indicator Circuit Needed
 

On Tue, 7 Mar 2006 18:33:53 -0500, "jon doe" wrote:

Hello:
Thanks to all for your thoughts.
I ended up doing the reed relay trick. I used 12awg wire, 4 wraps around the
body of the relay. It flickers just a bit, then locks on and gets my
indicator lamp running. I didn't want to use less then 12awg wire as I was
afraid of getting in trouble (the original cable is 10 awg). I could only
get 4 wraps, so I went with that......


"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



Glad it worked OK.
Two comments
1 A length of a smaller gauge rated to breaker would have had little
effect on voltage drop. (Compare to pump leads).
1 A length of 12 awg enamelled wire would have completely solved your
turns worries.

Its a neat trick for your type of application.
I originally read of it (about 40 years ago) as a bulb failure
indicator for cars.

Richard

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

Load In Use Indicator Circuit Needed
 

Thanks Richard


"Electricky Dicky" wrote in message
...
On Tue, 7 Mar 2006 18:33:53 -0500, "jon doe" wrote:

Hello:
Thanks to all for your thoughts.
I ended up doing the reed relay trick. I used 12awg wire, 4 wraps around
the
body of the relay. It flickers just a bit, then locks on and gets my
indicator lamp running. I didn't want to use less then 12awg wire as I
was
afraid of getting in trouble (the original cable is 10 awg). I could only
get 4 wraps, so I went with that......


"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



Glad it worked OK.
Two comments
1 A length of a smaller gauge rated to breaker would have had little
effect on voltage drop. (Compare to pump leads).
1 A length of 12 awg enamelled wire would have completely solved your
turns worries.

Its a neat trick for your type of application.
I originally read of it (about 40 years ago) as a bulb failure
indicator for cars.

Richard

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

Load In Use Indicator Circuit Needed
 

I have used this trick to turn on a hour meter, indicating the timer
the boat fridge compressor has run. Works well.
Klaus