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wolff
05-11-2006, 11:13 AM
I would like to hack into the existing··temp sending unit (on my boats diesel engine) and read (and display) the temp without interfering with·the existing gauge. I'm thinking it may require a super high impedance A/D converter or some sort of special circuit?
I'm hoping some one out there has experience with just this application. Any ideas?
Thanks all!
J
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steve_b
05-11-2006, 07:26 PM
Do you have an engine that might have frost plug ports?
you might try picking up an olding temp sensor from a scrap yard and seeing if you can get the stamp to read it (RCTIME probably). Then go about see if you can fit it in to a frost/heater port.

You can certainly pick up aftermarket gauges that will give you a digital readout as opposed to a bar scale with red yellow and green on it. But you'll want to make sure you don't 'skew' your readings by mismatching the impedances....thus, I'd try for a stand alone temp sensor (but that's just me).

Do you know what your existing temp sensor is?· A thermistor?· Is it part of a feedback circuit for air/fuel ratio's?

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

Post Edited (steve_b) : 5/11/2006 12:45:15 PM GMT

Bruce Bates
05-11-2006, 07:45 PM
wolf -

I have to agree 100% with the thought of ADDING a transducer, rather than trying to hack into an existing one. Any way you chose to "tap" into an existing line is going to compromise its present integrity. From my point of view, that's just asking for future trouble in a system that's very important in a diesel engine.

In an overheating condition, a gasoline engine may either seize and cause damage, or just shutdown. With a diesel engine overheating, you always have the potential of engine runaway, and you really don't want to be around if that happens!

Regards,

Bruce Bates

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steve_b
05-11-2006, 07:48 PM
Kinda off topic....but as far as diesel runaway goes. Some of the guys I work with used to work up at ALERT and other 'far north' stations.
The guy told me a story about their big deisel genset. They had actually put it on the 2nd floor of a concrete building as the snow would drift high enough that you'd eventually go through the 2nd floor door to get inside (like a 2 story outhouse).

Anyhow, he mentioned how the flywheel was this massive 6ft diameter 1ton beast. Apparently, when the bearings seized, the flywheel kept turning and tore itself lose....which it then proceeded to exit the building and drop through 15feet of packed snow.
They weren't sure where it went, but they couldn't go looking for it until the snow melted.
There's a real bad case of runaway!! haha

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

Jonathan
05-11-2006, 10:21 PM
Hi All,

I made a temp. sensor for my friends boat a couple of years ago. I simply took a compression fitting, the kind that uses a ferrol (sp?) and 1/4" copper tubing. An LM34 or LM35 fits perfectly into a 1/4" copper tube. I crimped and soldered one end, stuck the other through the compression fitting. The other end was 1/2" NPT fitting. Use some heatsink grease when you install the LM34/5, then epoxy the wires coming out of the tube, put some heatshrink over it all and you are done. I removed a plug from the cooling system and installed the sensor in it. It has worked fine for at least two years now.

One thing is that the soldering method is only really suitable for a heat exchanger with anit-freeze. I don't imagine the solder would hold up long with salt water cooling.

Another problem with using the exsisiting sensor is that it is 12V, and you will have to use a voltage divider to an ADC, reducing resolution. Not that fine resolution is really required for engine temp.

Jonathan

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wolff
05-12-2006, 05:53 PM
Jonathan,
I like your approach... Do you have any suggestions for oil pressure?

Thanks,

J