Wiring an audible alarm to bilge pumps

[jimg]

A friend has a boat with 4 bilge pumps covering different compartments of the boat and each is wired conventionally to the helm position on 4 switches each with its own light.
The question is, it possible to wire up a single audible alarm to the existing wiring to cover all 4 bilge pumps?

 

[cliff]

Yep - just need 4 diodes to prevent any pump back feeding the others.
--------------------

"Artificial intelligence is no match for natural stupidity"
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[jimg]

Cheers Cliff,
I thought diodes might be involved. I presume you take a live from each pump, but where does the diode go? Is there only one diode or are they rated in some way?
Cheers
Jim

 

[Stemar]

Take a feed from each switch to the alarm and put the diode in that line - 4 lines, 4 diodes. If the alarm doesn't work when you operate a switch, that diode's the wrong way round.

I'd be inclined to use a bit of veroboard (from Maplin or similar)to set it all up.

 

[cliff]

Beat me to it........ /forums/images/graemlins/grin.gif
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[jimg]

Cheers the both of you!
I will give that a try.

 

[Guest]

It is a little more complicated. I do not know what is "conventional" wiring. Normally there are multiple fuse/breakers. You do not run all the pumps from the same fuse. Then there is a control switch to select manual or automatic. Then there is the water level switch in the bilge. Any sensing of the voltage on the pumps with diodes has to be after all the switches. i.e from the pump connection. However, there is the problem of the alarm going off when manually washing out the bilges. Since alarms are so cheap and any single point failures are to be discouraged, in a safety system, just fit 4 alarms. Also depending on the helm switch you can wire it so that the alarm only works when on automatic. You need a 2 pole change over contact switch. The second contact is used to disable the alarm in the manual position.

What is the current system? Are they automatic?

 

[halcyon]

The problem with a simple system is that the alarm plays a tune as the boat rolls or pitches, moving water in the bilge and running the pump. Sealine use a 7 sec delay from the pump starting to the alarm sounding, it monitors 4 bilge pumps.

Brian

 

[Guest]

Sorry, too used to deep bilges or big boats.

Delays should be in the switch mechanism, as cycling a pump is not good either. Some switches have a reasonable type motion to stop nuisance switching. Two switches one either side also helps with nuisance switching. After seeing the effects of lightning I would keep this functionality to simple switch circuits.

 

[muckypup]

oh yes... Harlequin has that problem. The float switch is mounted quite low. If you close the throttle to slow down, any water in the bilge sloshes to the front and the alarm comes on (and the crew panic /forums/images/graemlins/shocked.gif)

My solution (and this was ChrisC's idea not mine) is going to be to have 2 bilge pumps in the engine compartment. I believe this is where a leak is most likely to happen.

A small one with built in float switch which will just work - quietly. I will then have the alarmed float switch moved further up. Thus if the small low flow rate pump can't handle the water in there, then I really want to know about it and it can sound the alarm and turn on the bigger pump.

S.

 

[jimg]

I was planning to take the feed from the auto side of the panel switch and take this to the alarm?

 

[Guest]

Only the current in the wires changes at that point. The voltage is always around 12v when the switch is in the auto position.

I would look at the wire back from the pump that connects to the Manual position. That should be from a point after the water level switch. Sensing voltage on this point is quite possible. The only way this point gets to 12v is if the float switch is activated in auto mode or just straight manual mode.

In this age of technology not to be able to draw diagrams for each other makes life hard.Sorry for the diagrams below. Keith the "code" setting is using a variable font.

<font class="small">Code:</font><hr /><pre>
Float switch
Auto /
/ o---------/ o---X-----------pump-------- "-"
"+"-----/ |
o------X-----------|
Manual |
|---->|---------z--------Alarm------ "-"
Diode

</pre><hr />

This way the Alarm goes off all the time in Manual mode and only when the float switch is activated in Auto mode.
<font class="small">Code:</font><hr /><pre>
Float switch
Auto /
/ o---------/ o---X-----------pump-------- "-"
"+"-----/ |
o------X-----------|
Manual |
|----------------|
|
| / o----------->|--------z--------Alarm-------- "-"
|-----/ Diode
o------
</pre><hr />

Assuming the 2 left side switches are the same switch this circuit only works the alarm in Auto mode.

I have drawn in the diodes if you want to go that way. The other diodes from other pumps connect at the z point.