VWDiesel.net The IDI, TDI, and mTDI source.
General Information => General => Topic started by: Vincent Waldon on March 23, 2008, 08:11:46 pm
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I promised y'all some pictures as I experiment with the Diesel Tiny Tach (http://www.tinytach.com/tinytach/diesel.php). If you just joined our broadcast, it's a digital tachometer with a transducer that bolts to an injector line... no W terminal needed. It acts like a tach but also has two service interval timers, a max RPM readout, and reverts to an hour meter automatically when the engine is off.
The display looks like this:
(http://i197.photobucket.com/albums/aa85/vwaldon/tiny_tach_display_800px72dpi.jpg)
(yes my idle is a bit high... it's either that or I lose a filling)
The transducer bolts to an injector line with two small hex head machine screws. In this picture I've bolted on another terminal (bright pink) so that I can attach an oscilloscope probe:
(http://i197.photobucket.com/albums/aa85/vwaldon/transducer_800px72dpi.jpg)
Here's the output signal from the transducer at about 1100 RPM for all you geeks out there:
(http://i197.photobucket.com/albums/aa85/vwaldon/signal_800px72dpi.jpg)
It's a pretty typical piezo transducer signal... a damped oscillation with amplitude about 60V and a period of 27 mS (37 Hz)...at this RPM... once per every two revolutions as injector #1 fires.
37 Hz / 2 * (60 seconds per minute) = 1110 RPM... cool dat.
It is a nice strong stable pulse, so the next step is to develop an interface circuit so that it can drive a standard timing light. With the right multiplier circuit it should be able to drive a gasser or diesel tach just fine as well.
The price for the entire unit has gone up 30 bucks since I bought this one, but the tranducer alone is still evidently quite affordable, particularly if it can become a timing light as well.
Other observations:
- the display is a good size and is backlit at all times
- having said that, the display is not really flush-mountable on the dash without wires showing etc. Not really an automotive form factor.
- the display has a pretty fast update rate (half a second or so) so great for monitoring RPM, setting the idle and max speed, etc... but probably too slow IMHO for shifting
Will post again when I have some circuitry developed.
Vince
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Cool! Thanks for the info.
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Neato!, did you get that in Edmonton somewhere or did you order it? Off the site its rather pricey-$95+shipping.
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Neato!, did you get that in Edmonton somewhere or did you order it? Off the site its rather pricey-$95+shipping.
There's a Canadian distributor in Markham.... Forster Instruments. They warned me the price was about to go up.. I got mine for $65 + shipping... and I guess they were right :cry:
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i wonder if you bought 4 transducer's if you could detect any injectors that are late in opening? that is a really neat option for those without tach's!
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Ho, make a gas tach conversion kit! I'll be your first customer for 2 Ea!
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Yeah, if you can just buy the transducer by itself for $35.00, and have a plug-n-play module to attach to your tach of choice, that would be the berries! Much better than farting around modifying stock tachs. You think Dakota digital would have an adapter gizmo to convert a transducer signal to something a tach could use?
Brendan
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i wonder if you bought 4 transducer's if you could detect any injectors that are late in opening? that is a really neat option for those without tach's!
Interesting, if perhaps a bit pricey !
The ability to "see" when an injector fires brings on all kinds of interesting possibilities.
My first experiment will be to temporarily install a 135 bar injector in #4 for a few minutes (the rest are 155 bar). By comparing #1 and #4 we'll then know *exactly* how much the ignition is retarded by a 20 bar difference in breaking pressure.
So much to do... so little time !!
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You think Dakota digital would have an adapter gizmo to convert a transducer signal to something a tach could use?
Brendan
Hmmmm.... they might. It will need to be a 4X multiplier rather than a 12X divider but ya never know.
Having said that, if they do have something it will probably be the better part of 100 bucks or so. I'm gonna restrict myself to parts found at your friendly neighborhood Radio Shack / The Source since they are pretty ubiquitous, and see if I can do it for 10.
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Go nuts Vince!
I'm down for two.
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+1
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You think Dakota digital would have an adapter gizmo to convert a transducer signal to something a tach could use?
Brendan
Hmmmm.... they might. It will need to be a 4X multiplier rather than a 12X divider but ya never know.
Having said that, if they do have something it will probably be the better part of 100 bucks or so. I'm gonna restrict myself to parts found at your friendly neighborhood Radio Shack / The Source since they are pretty ubiquitous, and see if I can do it for 10.
Vince,
If you want a good place for electronics go to Active Electronics, there in Edmonton. 6029-103rd St.(Gateway Blvd) 438-0644 8) :D
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If you want a good place for electronics go to Active Electronics, there in Edmonton. 6029-103rd St.(Gateway Blvd) 438-0644 8) :D
Excellent call dude... one of my shrines actually... along with Princess Auto and Lee Valley Tools. One of those stores you walk into and want to say "I'll take one of everything my good man". :wink:
However, not everyone has an Active Electronics in their neighborhood so I'll try to stick to parts from Radio Shack.... make 'em easier to source for the wide assortment of diesel folks out there ??!
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I assume you're also going to work out the details for a loop to run a strobo timing light, right Vince? :D
That's the plan... hacking the timing light pickup is just too crude... and some of us still have gassers to attend to every now and then. :cry: Spark plug... what's a spark plug ?! :roll:
You have a timing adapter right ?? Is your's a looper or a glow plug gazer ??
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I want to use something like this as an input to a computer.
Another input from a mark on the flywheel and I could watch the timing on a computer.... record/tune the advance curve.
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Another great idea.
In fact... VW thoughtfully providing a couple of raised lugs on the flywheel specifically to trigger a Hall-effect transducer inserted in the timing hole.
The lugs are on either side of TDC iirc so a little bit of math would be involved, but hey, that's what computers are good at. Or perhaps just physically offsetting the sensor would do it.
I'll build my interface to be 5V compatible... then you can use it as an input to a serial or printer port on your computer. Hall effect transducer to detect the flywheel lugs should be pretty straightforward as well... got some generic real-time graphing software in mind ??!!
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Hmmmm.... they might. It will need to be a 4X multiplier rather than a 12X divider but ya never know.
Having said that, if they do have something it will probably be the better part of 100 bucks or so. I'm gonna restrict myself to parts found at your friendly neighborhood Radio Shack / The Source since they are pretty ubiquitous, and see if I can do it for 10.
Yeah, I like your idea better. :D
Brendan
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If you want a good place for electronics go to Active Electronics, there in Edmonton. 6029-103rd St.(Gateway Blvd) 438-0644 8) :D
Excellent call dude... one of my shrines actually... along with Princess Auto and Lee Valley Tools. One of those stores you walk into and want to say "I'll take one of everything my good man". :wink:
However, not everyone has an Active Electronics in their neighborhood so I'll try to stick to parts from Radio Shack.... make 'em easier to source for the wide assortment of diesel folks out there ??!
All those are my shrines too. :lol: I'll walk in there and start drooling all over all the nice widgets and doodads... You're right, not everyone has an Active Electronics...
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digikey.com and newark.com are 2 online electronics warehouses, can find almost anything you need in electronics. Think they have a minimum order amout, like under $25 they charge you $5. Just buy more stuff. Might be a pain to do some searching and reading of data sheets but in my experience better than "Radio shack, you've got questions, we've got cell phnes." :lol:
Kind of wish I saw the transducer for fuel line before I ordered all the parts to make the opto sensor to schmidt trigger tach signal generator (schematics at 4crawler.com)
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So is someone going to make an adapter for a regular timing light to sell?
I think this would rock personally.