# Smoother capacitor for water pump



## Patrick_Phillips (Aug 17, 2006)

We had an Alden Netmaster 90 fitted last Tuesday to give us broadband access.
Everytime we turn on the water tap and the pump runs it powers down the modem for a few moments and have to wait while it resets
 
I guess that this is because the modem is very sensitive to voltage fluctuation caused when the pump kicks in.
My guess is that we need to put a capacitor across either the pump terminals or across the supply to the 12v modem (iCopter).
Anyone know what value this should be or even if my thinking is reasonable?
Has anyone had a similar problem and solved it?
Thanks
Patrick


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## hilldweller (Mar 8, 2008)

http://www.maplin.co.uk/Module.aspx?ModuleNo=498&C=Maplin&U=SearchTop&T=suppressor&doy=16m8

Put one of these across the pump supply and another across the contacts of the pump switch.

Might work, harmless otherwise.


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## geraldandannie (Jun 4, 2006)

Hi Patrick

I suspect you will need more than a capacitor. What capacity of leisure battery do you have? How old is it?

You might need to look at where the Alden gets its power from, and you may need to wire it direct to the leisure battery with thick cables.

Gerald


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## sallytrafic (Jan 17, 2006)

As Gerald says stiffening the supply (thick cables, checking for bad contacts condition of battery) should be first action. Sprinkling capacitors around your van can cause disguise real problems without effecting a proper cure.

The maplin contact suppressor isn't normally used in this context.


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## AberdeenAngus (Jul 26, 2008)

hilldweller said:


> http://www.maplin.co.uk/Module.aspx?ModuleNo=498&C=Maplin&U=SearchTop&T=suppressor&doy=16m8
> 
> Put one of these across the pump supply and another across the contacts of the pump switch.
> 
> Might work, harmless otherwise.


These suppress spikes not dips in voltage.
For that you'll need as big a capacitor as possible.
10,000 uF should do it. Make sure it's rated for at least 15 volts.

Agree with later comments though. The best protection against dips is a healthy leisure battery and good, thick cables for your pump.


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## hilldweller (Mar 8, 2008)

AberdeenAngus said:


> These suppress spikes not dips in voltage.


I know that, I've fitted hundreds of them.

There is no evidence whether there is a serious voltage drop or if it's a spike that is causing the problem.

I think that there's a load of bollox being spoken as is usual in here. I appears this has been professionally fitted. I would assume the dish is supplied with cables of the correct specification. I would assume it actually takes a small current and there will be negligible voltage drop on the cables therefore fitting beefier cables serves no purpose.

Fitting "good thick cables to the pump" exacerbates the problem because it may then draw even more current.

As someone said, finding out where the installer has taken the dish power from would be a good idea.


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## aultymer (Jun 20, 2006)

> Fitting "good thick cables to the pump" exacerbates the problem because it may then draw even more current.


How does that happen?
Sorry, I am a simple hammer man not leccy trained at all.


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## hilldweller (Mar 8, 2008)

aultymer said:


> > Fitting "good thick cables to the pump" exacerbates the problem because it may then draw even more current.
> 
> 
> How does that happen?
> Sorry, I am a simple hammer man not leccy trained at all.


If the cables to the pump are thin they will act as resistors and limit the current the pump can draw. Of course the pump is ( probably ) a manufacturer designed in component and the cables should be perfectly adequate for the job.

So if it is, and it may be, the current of the motor dropping the voltage that trips the dish then drawing more current will drop more voltage.

Faults like this are very difficult to trace, when the problem may last only a microsecond you need the right kit to trace it or you use experience and take a stab at it or to put it another way guess 

What I suggested might work, if it fails it's cost a whole fiver.


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## sallytrafic (Jan 17, 2006)

hilldweller said:


> AberdeenAngus said:
> 
> 
> > These suppress spikes not dips in voltage.
> ...


"bollox"

Hmmm

Well checking the alden connections wouldn't go amiss and also its cable voltage drop. Always check the simple things before adding stuff. The range of voltage DC quoted by the user manual is only down to 11.5V. So if for example you were getting a half volt drop on the cables/connections to the modem the starting transient of the pump might just be tip the balance.

The better the battery the more likely that the voltage will not dip below 11.5 even in a transient.


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## AberdeenAngus (Jul 26, 2008)

hmmmmm indeed

If you had the option then ideally there should be two 12v systems in the van. A "power" system for pumps & lights etc with nice, fat , cables and then a second loop for sensitive electronic stuff like modems etc. This could be lighter cables but would be properly smoothed and suppressed.

But to address your present problem, if you have a multimeter, put it across the modem supply, then start the pump. If its a dip, you should see it. If its a spike however you won't, unless you have an oscilloscope as it will be too fast for the meter.

It could be either (or both), neither the suppressor capacitor nor the larger smooting capacitor will do any harm. You could try them both.
By the way, the larger capacitor will have a polarity. Don't get it wrong or you'll toast the capacitor.

Curing noise problems is all about perserverence


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## aultymer (Jun 20, 2006)

> I think that there's a load of bollox being spoken as is usual in here.


Never a truer word written.

But the rest of the forum has a better idea of wots wot.


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## Patrick_Phillips (Aug 17, 2006)

Thanks to everyone for the comments so far.
Hilldweller - I will certainly try the suppressor. As you say it risks virtually nothing.
Geraldandannie - The leisure battery is a 110aH Lucas AGM bought at the Peterborough show in April. The power for the modem etc (not the main dish motor which was taken from the main cable to the distribution box) was taken from the unused "Radio" connection on the distribution panel and the spare negative on the same connection bar. This means that the Linksys access point, Zehender digibox and the modem are all on one fuse unique to them.
AberdeenAngus - I only have a domestic type digital multimeter which certainly sees nothing - they aren't very quick to register at the best of times and my wife won't let me take a scope... I'll get the capacitor (or is it condensor these days) rated at 50v to play safe and see what that does.
The odd thing is that it does its trick even when on EHU with a big hefty charger feeding the battery!
Thanks all again


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## aultymer (Jun 20, 2006)

> This means that the Linksys access point, Zehender digibox and the modem are all on one fuse unique to them.


If they are all connected to a terminal which was only wired for a radio there is a chance that the wiring to that point is not man enough to now power the 3 new items and that the voltage drop on this terminal is taking you near the cut off for one of your hi tec components.
Without spending anything, you could disconect from the radio terminal and take a heavy wire from your battery to the feed to your new boxes and test by switching on the pump.
That would save a trip to Maplin and a fiver if it works.


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## Patrick_Phillips (Aug 17, 2006)

Thanks, Aultymer, that is a reet good idea. I'll try it in the morning when its light again...


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