clamp ammeter

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I am designing a remote control for a large diesel engine and I was thinking that I could measure the current flowing through the starter motor to determine when the engine has started.

My question is wheather anyone know of some clamp hall-probes I could use with the ADC on the AVR to measure this current. The current would be in the range 0-1000A.

Simon

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You could use a "Hall " sensor made by Allegro at
http://www.allegromicro.com/en/Products/Part_Numbers/0756/index.asp
Allegro has several offerings.

As the magnetic field intensity is inversely proportional to the distance from it's source, you could mount one of the above, some small distance from the current carrying wire and easily tell if a motor is running.

But... Just measuring the current through the starter motor won't tell you that the diesel engine is actually running. Once the diesel engine has started and the starter motor has turned off, how will you know that the diesel engine had actually started, that it is in fact running, and/or that it hasn't stalled?

Maybe a sensor monitoring a rotational part of the diesel engine would be a better indicator.

If you see a pulse at about 1/4 second intervals, the diesel engine is running. If you don't see pulses for say, a 1/2 second, the diesel engine didn't start.

Maybe don't use pulse detection... Maybe use frequency and, if the engine RPM falls below say, 100 RPM, or some reasonable number, the engine is determined to have not started and is in fact not running. If the RPM monitor reads above 100 RPM, the engine has successfully started, and is in fact running.

This RPM monitor could be nothing more then a magnetic proximity sensor driving an RC network and diode that develops a voltage proportional to the engines RPM. The derived analog voltage would then drive a comparator that is set to trigger it's output when the voltage reaches some minimum value, based on the engines RPM.

Of course, an AVR A/D channel or the internal comparator would work, as well.

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

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LEM DHAB http://web4.lem.com/hq/en/compon... ... utput_type

Imagecraft compiler user

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bobgardner wrote:
LEM DHAB http://web4.lem.com/hq/en/compon... ... utput_type

I completely forgot about LEM current sensors.

I have designed a few of them into some of my work, but stopped using them because they are so expensive. One 50 Ampere unit that I've used cost me more then $40.00US.

I have about 20 or so LEMs in the parts bin that I recovered from some discarded variable frequency drives. The issue there is that they have OEM part numbers and I have no way to cross them to the LEM part numbers, if there is even an equivalent to a standard LEM part.

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

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How about a thermocouple in the exhaust manifold? Wouldnt that start gettin hot real fast after the motor started running? Or a 50 cent electret microphone near the exhaust pipe. When it hears POWPOWPOW about 2500 times a minute, its runnin!

Imagecraft compiler user

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I guess current monitoring wasn't very good. There is a RPM indicator on the panel of the engine, I am pretty sure it gets it's signal from the generator (edit: alternator) in some way. If I had the machine in reachable distance and owned a scope I would find out. This would be a very good solution since I will have to monitor RPM anyway.

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simonpe wrote:
I guess current monitoring wasn't very good. There is a RPM indicator on the panel of the engine, I am pretty sure it gets it's signal from the generator in some way. If I had the machine in reachable distance and owned a scope I would find out. This would be a very good solution since I will have to monitor RPM anyway.

Surely there is somewhere that you can mount a proximity sensor to detect engine drive shaft rotation.

No engine drive shaft rotation pulses = engine not running.

Detection of drive shaft rotation pulses = engine RPM (with proper scaling) and engine running.

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

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microcarl wrote:
simonpe wrote:
I guess current monitoring wasn't very good. There is a RPM indicator on the panel of the engine, I am pretty sure it gets it's signal from the generator in some way. If I had the machine in reachable distance and owned a scope I would find out. This would be a very good solution since I will have to monitor RPM anyway.

Surely there is somewhere that you can mount a proximity sensor to detect engine drive shaft rotation.

No engine drive shaft rotation pulses = engine not running.

Detection of drive shaft rotation pulses = engine RPM (with proper scaling) and engine running.

Why not use the same signal as the tachometer?

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Bob! I'm shocked! I thought for sure you were going to suggest an audio solution! A mic to pick up the engine note would be good. hehehe

Go electric!
Happy electric car owner / builder

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sgomes wrote:
Bob! I'm shocked! I thought for sure you were going to suggest an audio solution! A mic to pick up the engine note would be good. hehehe

That is probably how Bob generates the base tones for his Boom-Boom box. It's all timed to the engine RPM!

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

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base? bass? bass? First one is used in the National Pastime, second one is a slap fiddle, third one is a big mouth fish.

Imagecraft compiler user

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The acoustic sensor is a good idea. You could also use it to check if the engine is running right. It's possible diagnose many engine problems just from the sound.

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Quote:

I completely forgot about LEM current sensors.

I have designed a few of them into some of my work, but stopped using them because they are so expensive. One 50 Ampere unit that I've used cost me more then $40.00US.


Your LEMs are quite inexpensive compared to those purchased by NASA some years ago for about US$100 million per each.

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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theusch wrote:
Quote:

I completely forgot about LEM current sensors.

I have designed a few of them into some of my work, but stopped using them because they are so expensive. One 50 Ampere unit that I've used cost me more then $40.00US.


Your LEMs are quite inexpensive compared to those purchased by NASA some years ago for about US$100 million per each.

Lee

I think we're talking about two different things here, Lee. :wink:

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston