Engine Running Sensor

[Quattrodave]

I'm trying to think of a way to detect if a mechanical diesel engine is running, originally I was just going to use the alternator output but that would rely on the alternator working and belt intact and not slipping.  Ideally needs to be robust and reliable.  I did think about putting a hall sensor on the flywheel but wondered if there was simpler solution??

 

Thanks

 

Dave

 

Edit

Also thought about a VR sensor on the flywheel which could be triggered by the teeth but that would require more complex driver circuitry...

Edited August 3, 2023 by Quattrodave

[David Mack]

Is the Mark I ear not good enough?

Or use the oil pressure sensor.

[Rob-M]

Just now, David Mack said:

Is the Mark I ear not good enough?

I had the same thought.

[Tracy D'arth]

Simply, why?  I am in no doubt when a diesel is running. Are you thinking of remote control starting?

[Quattrodave]

OK the back ground is that a good friend has a buzzer which goes off in the event of oil pressure loss, charging loss or over heating.  Its really annoys him that the buzzer goes off when he's starting the engine.  So I figured it would be easy to only have the buzzer active when the engine was actually running.  But being a mechanical diesel there are no electronics to take a 'running' feed from so now I'm a little stumped....

[cuthound]

Many years ago.i did a BT course on diesel maintenance. The control system was a "ratchet relay" a bit like the old mechanical washing machine programmers.

 

As they only had one real diesel engine, they gave each student a board with the ratchet relay on the back and the engine control panel lights on the front. Also on the back were a series of dip switches which the lecturer used to select various faults for the students to find.

 

I quickly progressed through the faults and eventually the lecturer said "right let's see if you can find this one".

 

Try as I might I couldn't find any fault, all seemed normal to me, so went to the lecturer to say so.  

 

"There are actually two faults" he said. One the engine hasn't started and two the supply to the engine run warning light has failed in the on position".

 

I lost my temper and said, "if it was a real engine I would have noticed that it hadn't started even though the run light was lit, because my ears work!"

 

He just laughed and said "no one had ever got that fault!".

Edited August 4, 2023 by cuthound
phat phingers

[BEngo]

Nettle the buzzer!

 

N

[David Mack]

I would need to think about the detail, but I would have thought you could arrange some sort of latching relay setup controlling the buzzer that initiates when the oil pressure sensor first cuts in after turning on the electrics, but which would still sound the buzzer if the oil pressure subsequently fails. The system would have to reset when the 'ignition' is turned off.

I suggest you would still want the warning lights operating in the normal way as that tells you that the warning systems are working.

[Tony Brooks]

4 minutes ago, Quattrodave said:

OK the back ground is that a good friend has a buzzer which goes off in the event of oil pressure loss, charging loss or over heating.  Its really annoys him that the buzzer goes off when he's starting the engine.  So I figured it would be easy to only have the buzzer active when the engine was actually running.  But being a mechanical diesel there are no electronics to take a 'running' feed from so now I'm a little stumped....

 

The buzzer works that way in the same way as the charge and oil pressure warning lamps. It indicates that the buzzer has not failed each time the engine is started. If he is so concerned about the alternator failing in some way, I would have thought he would be just as concerned about the buzzer (or more likely) it's associated soldering and diode board failing. In any case, if the alternator did fail totally, the charge light would tell him.

[Tonka]

15 minutes ago, Tony Brooks said:

 

The buzzer works that way in the same way as the charge and oil pressure warning lamps. It indicates that the buzzer has not failed each time the engine is started. If he is so concerned about the alternator failing in some way, I would have thought he would be just as concerned about the buzzer (or more likely) it's associated soldering and diode board failing. In any case, if the alternator did fail totally, the charge light would tell him.

The overtemp circuit never gets tested

[Tony Brooks]

12 minutes ago, Tonka said:

The overtemp circuit never gets tested

 

This is true unless you test it, but even then you can't test the switch without heating it in some way. However, an overheat will not immediately damage the engine like a loss of oil pressure will.

[MtB]

42 minutes ago, BEngo said:

Nettle the buzzer!

 

N

 

Totally agree. I snipped the wires on the buzzer on my BD3 and starting it changed into BLISS. 

 

I can clearly hear the buzzer on pretty much any boat being started up to about a hundred metres away, they are so loud. Drives me demented.

 

 

[GUMPY]

 

49 minutes ago, Quattrodave said:

OK the back ground is that a good friend has a buzzer which goes off in the event of oil pressure loss, charging loss or over heating.  Its really annoys him that the buzzer goes off when he's starting the engine.  So I figured it would be easy to only have the buzzer active when the engine was actually running.  But being a mechanical diesel there are no electronics to take a 'running' feed from so now I'm a little stumped....

 

A delay timer on the buzzer, say 30 seconds, Ignition on you have 30 seconds to start it before it sounds.

Dare I say a 555 timer would be ideal for the job

 

[Tonka]

1 minute ago, MtB said:

 

Totally agree. I snipped the wires on the buzzer on my BD3 and starting it changed into BLISS. 

 

I can clearly hear the buzzer on pretty much any boat being started up to about a hundred metres away, they are so loud. Drives me demented.

 

 

No you did not. When you were selling the BD3 you made a video and the buzzer can be clearly heard 

[TheBiscuits]

I just stuck a lump of tape over mine, you can still hear it but it's not painfully loud anymore.

 

Sometimes it pays to keep it simple!

[Quattrodave]

48 minutes ago, Tony Brooks said:

 

The buzzer works that way in the same way as the charge and oil pressure warning lamps. It indicates that the buzzer has not failed each time the engine is started.

Yup thats a fair point.  I suppose it also acts as a 'you've left the ignition on' reminder too...

 

50 minutes ago, Tony Brooks said:

In any case, if the alternator did fail totally, the charge light would tell him.

And the buzzer would go off. Buzzer will go off on oil pressure failure, charge failure or overheat.

 

10 minutes ago, GUMPY said:

A delay timer on the buzzer, say 30 seconds, Ignition on you have 30 seconds to start it before it sounds.

Dare I say a 555 timer would be ideal for the job

Ooooh thats a good shout!!!

[GUMPY]

4 minutes ago, Quattrodave said:

Ooooh thats a good shout!!!

https://www.ebay.co.uk/itm/192414845824?

 

[Quattrodave]

13 minutes ago, GUMPY said:

https://www.ebay.co.uk/itm/192414845824?

 

Thank you, I'd just found the same thing 😁

[PeterF]

An accelerometer chip or vibration sensor mounted on the engine would indicate if it was running.

[nicknorman]

I don’t really understand what is so bad about a couple of seconds buzzing before the engine is started, and as has been mentioned it’s an important part of engine safety - checking that the buzzer actually works. Rather than permanently disabling it during start, why not just have a normally closed pushbutton that eg breaks the ground connection on the buzzer when pressed. The owner just has to hold that button down for a few seconds whilst the engine is started if he finds the noise unbearable. And the integrity of the buzzer can still be checked from time to time by turning on the ignition without pressing the button.

[PaulJ]

^^^^

Thats a nice and practical KIS approach..

[MtB]

1 hour ago, nicknorman said:

I don’t really understand what is so bad about a couple of seconds buzzing before the engine is started, and as has been mentioned it’s an important part of engine safety - checking that the buzzer actually works. Rather than permanently disabling it during start, why not just have a normally closed pushbutton that eg breaks the ground connection on the buzzer when pressed. The owner just has to hold that button down for a few seconds whilst the engine is started if he finds the noise unbearable. And the integrity of the buzzer can still be checked from time to time by turning on the ignition without pressing the button.

 

I like this idea. 

 

Where do I find this wire on my Kelvin K2?

 

Thanks...

 

 

 

[magnetman]

Bicycle computer. 

 

Some of them switch off automatically when no motion. It would only be a visual indicator not a sound.

 

Put the magnet on the flywheel. You can also get RPM from it. 

 

 

Or maybe a bicycle dynamo against the flywheel wired to a relay. 

 

Or a dynamo and a lamp in a box and a light detecting circuit driving a relay. 

 

 

[Mikexx]

I presume a simple buzzer arrangement is an issue where it sounds when you are in the glow-plug heat position. Otherwise as already said, it is a means to test the buzzer.

 

I can think of two solutions.

1) Connect the buzzer to the ignition warning light aka Ind terminal so the buzzer is fed from the excitation side and only live when the alternator is running.

2) Put a relay in parallel with the charging warning lamp and use n/c contacts to fee the buzzer.

 

The chances of two faults, the alternator failing as well as losing oil pressure is pretty remote, without someone noticing. Plus the oil lamp would still work as intended. I suppose a variation is to use the glow plug feed for the relay, that might discourage too short a heat time.

[GBW]

I have the same interest and found this post by accident.

My reason us that I have a fear of engaging the starter motor while the engine is running.

To preempt the incredulity, I have two identical buttons adjacent to each other, one for start, the other for stop.

I have a remote "start down", "stop up" toggle switch at the helm.

I also have a wife who can't remember which switch to push or toggle.  If she pushes "start" when she meant "stop", there will be a horrible noise and the chance of damage.

I am happy with the arrangement, as, in the engine bay, I can select which button by touch and at the helm, "Up" means stop and "down" means start.

All perfectly logical BUT .............!

If I can detect the engine is running, I can disable the circuit to the start solenoid.  The oil pressure switch doesn't do it as the starter would cease once the oil pressure rises.

Likewise, the alternator would not serve for the same reason.

Even a pulse detector on the crankshaft would present the same problem.

 

However, as is often the case, describing the problem to others inspires a solution.  A delay in the detection signal produced from any of the above, should solve the problem.

 

Thanks for the invitation for self reasoning!🙂