Exhaust Alarm

BlueLancer

BlueLancer

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The latest PBY has an article describing how to build a very useful exhaust alarm for about £15.00. Does anybody know if it can be used for two exhausts to provide separate indications ie port alarm and starboard alarm. I envisage using two separate sensors but how would it be wired at the PCB.The obvious answer would be to build two separate alarms but being a tight yorkshireman .......
 
Turn off one engine - you'll soon save enough money to pay for a second alarm! Having two alarms will allow you to know which exhaust is overheating.
You could buy a second thermistor and wire both in series but you would not know which of the two exhausts was overheating.
 
I'm glad you found it useful, but if you have two exhausts I'm afraid you need two alarms. If you connect two thermistors in either parallel or series you'll have to re-calibrate everything.

Cheers, David Berry
 
whiteoaks7 said:
I'm glad you found it useful, but if you have two exhausts I'm afraid you need two alarms. If you connect two thermistors in either parallel or series you'll have to re-calibrate everything.

Cheers, David Berry
Click to expand...

Thanks for the help Dave, excellent article.Now if you could turn your mind to a DIY bilge alarm, intruder alert, battery fail monitor with mobile alert :D
 
whiteoaks7 said:
I'm glad you found it useful, but if you have two exhausts I'm afraid you need two alarms. If you connect two thermistors in either parallel or series you'll have to re-calibrate everything.

Cheers, David Berry
Click to expand...

Hi David, great article and description and just what I need, I have ordered the parts today and will have somemfun putting it together next week.

Quick question, any thoughts on the best way to secure the thermistor to the exhaust? I suppose the obvious solution is under a jubilee clip taking care not to crush it, but anyone got any better ideas?
 
I recall that a previous solution using thermistors had it tucked underneath the rubber exhaust hose - I'd guess trapped between the two jubilees would be a good idea.
 
Bilge alarm

BlueLancer said:
Thanks for the help Dave, excellent article.Now if you could turn your mind to a DIY bilge alarm, intruder alert, battery fail monitor with mobile alert :D
Click to expand...

There are Velleman kits that would help with a bilge alarm (if you go to my website there's a page with a list of all the articles Ann and I have written so you can get the issue/number and refer back - okay, it's a way of getting you to look at the site but you might find something interesting / contentious there).

Battery fail monitor - I once made one of these for a previous boat, once the battery voltage dropped below a certain value a buzzer sounded, drew more current - and hastened the demise of the battery...
:-( ...so I took it off.

As for fixing the thermistor, I scraped the paint off the elbow and glued it in place with epoxy making sure the thermistor body was touching the metal. If you're going onto a rubber exhaust then I agree some way of binding it should work.

Cheers, David Berry
 
Hi David. Just regular epoxy like araldite or something more heat resistant?

Also, can I ask one more question? My engine is under my deck saloon and that means a longish cable run up to where I can hear the alarm. Am I better to keep the thermistor cable run short as opposed to the piezo buzzer? Sorry if this is a stupid question.

Best wishes

Piers
 
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I think most epoxies would do it - the temperature on mine is only about 35C which I think is typical but if it's higher you might need to think again. The resistance of the wire won;t matter much whichever way around you do it - I suggest you place the box somewhere convenient so that you can twiddle the knob to fine tune the sensitivity and adjust one or both wires to suit. If you want more noise Maplin sell a really loud screetcher (I've got one on my gas alarm) so you could use that.

David Berry
 
Puggy said:
Quick question, any thoughts on the best way to secure the thermistor to the exhaust? I suppose the obvious solution is under a jubilee clip taking care not to crush it, but anyone got any better ideas?
Click to expand...

The easiest and quickest way is to secure it with a piece of gaffer tape onto the metal part of the exhaust elbow and wrapped round a couple of turns.

The temp doesn't get very hot under normal conditions, and if it goes over 95 degrees or so your alarm will sound anyway. Much quicker than epoxy and easier too, although arguably not as elegant in engineering terms. Mine's been in 2 years now and no problems.

I found jubilee clips clamp with too much force.
 
It's a neat looking kit but beware - the clever bits of it have a large number of tags very close together. Soldering them without making accidental bridges between them is going to be a real challenge!
 
David, I dont have the PBO article but I know the kit youve used as I use one for my fridge thermostat. My electronics knowledge is very rusty so .. Did you just change the value of R4 to reset for a higher temperature range? Id guess changing R4 to 25K would reset the range for between 30 and 70 degrees ?
Rgds Steve
 
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