Pump running indication

[RayS]

My new caravan has an inboard pump which is capable, they say, of running dry witout damage.
The pump switch on controls panel has a light but this only indicates the pump is powred, not whether it is running or not. The pump is very quiet and so sometimes we have actually had it running for some time without delivering water. The pump obviously has an integral pressure switch.
What I would like to do is to fit a current sensing relay to power a pump running light in addition to the pump powered light.
50years ago I made my own version of the Hella relay commonly used to detect caravan turn indicator bulb failure. This was mainly a simple coil of suitably sized wire connected in series with the turn indicator bulbs. Inside this coil I put a reed switch with a suitable protective shunt resistor which switch a further electro mechanical relay flashing a lamp in sympathy with the turn indicators unless one of their bulbs had failed.
Worked well for many years and I had many requests to make and sell, but the day job did not permit.
Anyone know a modern day equivalent please. A quick Google search has produced many big complicated ac and dc power devices but nothing simple, small, and cheap, so hence my enquiry

 

[otherclive]

My own caravan water pump behaves exactly as does yours, but the pump isn’t exactly quite so we can hear if it runs on. I had a 2005 Bailey Series 5 Pegeant which did have a pump running light, which was useful as that pump was quite. If you could find out what that caravan used to highlight pump running that might give a link to some hardware.

 

[RayS]

I think that caravans with a light showing pump running rather than just powered used either in line pressure switches or had taps with microswitches in the taos. With the onboard pump the pressure switch is bult in to the pump. Some ob board pumps e.g. Whale do actually have a third lead for a running light but mine and a Shuroflo I had previous do not.
Hence the need for a relay or device that will sense current flowing rather than just voltage existing.This is the same requirement as the 'bulb failure' warning systems which detect an open circuit condition rather than specifically bulb filament failure.

 

[xtrailman]

My last caravan inboard pump would run silent when it was on air, the led indicator was difficult to see so I fitted a buzzer across the pump.

 

[Icaru5]

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[Icaru5]

I was thinking about a potential solution using a miniature relay and a couple of diodes ...

Then I had a quick look at RS, Farnell and Maplin for a couple of alternative solutions and there seem to be quite a few Hall effect sensors that I thought might be suitable, but then I stumbled across this, looks perfect for the job !

NK DS1 Current Sensing Switch

 

[ProfJohnL]

It seems the intend purpose of the OP's request is to be able to provide some visual indication when the pump runs. when there may be no water to pump. That would be quite difficult scenario to meet with a lamp, it would require a limit sensing circuit, and possibly a float switches in the water tank. It all becomes quite complicated, but there is a simpler solution that could also detect another fault condition. The downside is the display would require interpretation by the observer. This can all be looked at in terms of current used by the pump

So in addition to the pump:-
being isolated (zero Current)
Pump running no water (Low current)
normal pumping of water (Medium Current)
Trying to pump water with the taps turned off (High Current)
Pump short stalled or short circuit (maximum Current)

Fitting an analogue ammeter in series with the pump supply would provide 5 readings which will indicate the above conditions. The problem is the user would have to familiarise them selves with the currnet ranges for the pump they are using.

There is no easy way to achieve the same scope of information with an on off lamp.

 

[Icaru5]

I don’t think that the OP was wanting an indication of multiple conditions Prof, just that the pump is running ?

The Switch in my post switches at 0.75A. Not sure what the pump would be pulling when running dry, but I would certainly imagine more than this ?

 

[ProfJohnL]

I don’t think that the OP was wanting an indication of multiple conditions Prof, just that the pump is running ?

The OP can make their own mind up whether to use the scheme I have suggested and can benefit fro a greater range of information or as little as they wish.