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Griff

Flickering LED's

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Our new caravan has quite a number of roof inset LED single down lighters around it.

 

Have noticed that when the lights are off and whilst using the on-board water pump, as the pump reaches the end of its pumping cycle the LED's flicker on and off for an instant.

 

No big deal and will mention it to the dealer next time of speaking but wondered what is the most likely cause of this.

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LEDs are much more prone to flickering than filament bulbs because a filament bulb takes a few milliseconds for the filament to cool enough to stop glowing but an LED will dim almost instantly if there is any dip in supply voltage.

If you look at video of car rear lights, filament bulbs appear to be continuous but LEDs will often appear to flash because the normal flickering which is too fast for the naked eye to see  is out of phase with the video frames.

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Thanks for that which I can understand but in my case the lighting circuits are switched off.

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1 minute ago, Griff said:

Thanks for that which I can understand but in my case the lighting circuits are switched off.

If it's  Swift, it's a well known problem for which a fix is available by the dealer or you could contact Sargent direct and they will send it to you. I believe it's a resistor fitted across the pump terminals.

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15 minutes ago, Legal Eagle said:

If it's  Swift, it's a well known problem for which a fix is available by the dealer or you could contact Sargent direct and they will send it to you. I believe it's a resistor fitted across the pump terminals.

 

:Thankyou:

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Hmm mm. 

Saw this earlier and was going to post but I thought someone with more up to date tech savvy might help.

I could be spouting rubbish - it wouldn't be the first time!

 

So, my immediate thought was that as you switch off the pump (or it gets switched by the pressure sensor), the pump will still turn for a (very) small period under its own inertia and the flow of water.

This means that the motor on the pump is now acting like a dynamo, and producing a voltage. I would suggest that if there is a poor earth somewhere (good luck with finding that one 😊) the voltage spike produced may be enough to fire the LED into action.

Rather than a resistor across the pump, I would suggest a reverse bias diode across the pump terminals will swiftly damp any ringing caused by pump overrun.

To reiterate, I could be talking rubbish. Little knowledge is dangerous!

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46 minutes ago, AlwynMike said:

Rather than a resistor across the pump, I would suggest a reverse bias diode across the pump terminals will swiftly damp any ringing caused by pump overrun.

To reiterate, I could be talking rubbish. Little knowledge is dangerous!

As I say, if it's a Swift caravan the problem is well known and the cure is actually the fitting of a MOV suppressor.

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A diode, reverse biased will stop the inductive spikes when the pump switches off, more reliable and more appropriate than a Metal Oxide Varistor.

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Will give Sargent a call tomorrow and see what they have to say, caravan is only a few weeks old.

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