I will draw some pictures later. If you know the basic concepts perhaps you can help me brainstorm a fix for this issue.

I have a timing probe (snapon mt480) for GM / Ford 7.3 liter IDI diesels. It uses Hall effect on the harmonic balancer and detects a groove in the balancer.

I want to use this on a Benz, which has a protruding dowel on the crank pulley.

I tried hooking up a stock MB crank sensor to the harness of the Gauge I want to use, but it did not like the signal.


Thoughts?


......Other than removing the dowel and grinding a groove in the pulley.

Obviously it is a signal incompatibility issue at best.

If you modified the balancer you would also need a sensor from the Ford system to accomplish anything correct? Because it sounds like the two systems are functional opposites, the Ford detects a decrease in ferrous proximity and the MB detects an increase in ferrous proximity. So the electronics and signals of these systems are probably very different.

It may not be worth the effort, but rather than changing or adapting the mechanics or electronics of the system a more elegant solution might be conditioning the available signal to transform it to a signal more palatable to the test instrument.

You would start that by capturing the signal waveform from the two systems as they where designed to operate and then someone would need to devise some type of signal conditioner to accomplish the translation. This could be relatively simple or could be something more complicated and not worth pursuing. There are electrical engineers who are forum members who would be most likely able to give an appraisal as to what could be done most easily if they had the wave forms to compare them. Today there is a vast array of ICs some of which with a couple discrete components might accomplish the desired effect. There might even be a niche` market for an aftermarket module that could accomplish something like that.

With some research you might even find the timing signal waveforms somewhere on line that could give you a rough idea of the parameters involved.

If you’re an inquisitive fellow with a little time on your hands, do a web search and you will find freeware which can allow you to use the soundcard of a computer as a digital recording oscilloscope, a program such as this and a test lead can be used to detect signals and then generate a time/amplitude pictures of the waveforms. The frequency upper range limit is not that high but if the signals used in theses systems are single RPM events a simple setup like this should be able to do the trick.

Here’s a quick list of stuff like this!

http://www.google.com/search?hl=en&source=hp&q=Sound+card+O-scope&aq=f&aqi=&aql=&oq=&gs_rfai=CxgdqpxnWTPOnFIiwyASXxcjWDwAAAKoEBU_QsUX6

I think that MB sensor is a 2 wire permanent magnet type and will not generate the square wave signal that the halleffect sensor does.

the MB has three leads to the crank sensor.... I am not sure if you mean something else.

I have opened one up out of curiosity (good estimation, Billybob), and it is a permanent magnet surrounded by wound wire.

Mr. Bob,

I think you have at least provided a good springboard. Thank you.

Have you got an oscilloscope or a fancy multimeter that allows you to see the output of the signal?

Without some some sort of measuring equipment you'll just be guessing

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I don't know that the OP does, but for anyone who likes to fool around with anything like this I posted this. It's free and it's fun if anyone is trying to do something like this. So I'll post it again because it's cool!

"If you’re an inquisitive fellow with a little time on your hands, do a web search and you will find freeware which can allow you to use the soundcard of a computer as a digital recording oscilloscope, a program such as this and a test lead can be used to detect signals and then generate a time/amplitude pictures of the waveforms. The frequency upper range limit is not that high but if the signals used in theses systems are single RPM events a simple setup like this should be able to do the trick.

Here’s a quick list of stuff like this!

http://www.google.com/search?hl=en&s...AAAKoEBU_QsUX6"

Most of these programs also can be configured as spectrum analyzers in the audio frequency range. I've never yet made use of it but I suspect that something like that may be useful in diagnosing vibrations emitting from a running or moving vehicle. You might be able to visually observe the graphical representation of a vibration at the same time as you hear/feel it in the car. The specific frequency of that event could help differentiate if it coincided with engine RPM or some harmonic of that, or if the frequency was related to some rotational element of the drive train like a drive shaft, diff, axle, or wheel. One of the interesting things I picked up along the way is a sensor for detecting audio frequency waves which is very inexpensive, common and effective, is a piezo-electronic transducer most often used as a buzzer in electronic equipment. Usually there is a thin brass disk with a sliver of piezo material cemented to it. They have one lead attached to the brass and the other attached to the pieso material. This device will detect virtually any touching of it; clamped to a surface it will detect any vibration (I originally used one as a pick-up for an acoustic guitar many years ago and as a sensor for synthesized drum pads). I've used one held against a machine with a clothesline clip to capture vibration wave forms.

I'm all but certain that one could be used very effectively to detect injection pulses in diesel injector fuel lines. With one of these Sound Card PC O-Scopes one could detect and visually compare TDC waveforms and Start of Delivery waveforms simultaneously using the scopes dual trace capability.

I agree it is quite amazing what can be achieved with a sound card and a PC and I have bit of experience of this. I'd never bother with a machine that is running windows as an operating system as it will nearly always bugger up your measurements... (It just won't do what is told)

My main problem with this sort of data acquisition, though, is that sound cards tend not to have anti-aliasing filters - as an acoustician I get in a bunch about that sort of stuff. (Sorry)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

funny you should mention, Mr Bob.

this project is related to another, previous and currently struggling project.

I was aware and following the progress of that now pretty dormant thread in the past, although much of the discussion took place when I was in "exile"!

I'll just post a thought or two here regarding that project.

Dedicated multi-trace PC based O-scopes can be had for around $100-200 on eBay, there are numerous 5 trace scopes available, the frequency range occurring around these engines is quite low and any of these cheap scopes should be able to easily capture and present waveform data.

From a design standpoint regarding developing an instrument one way I would look at it from a perspective where I would try to make use of the physical/mechanical circumstances and avoid making use of the electric/electronic circumstance that are inherent to these engines. Identifying, quantifying, and some how adapting the signals will probably be somewhat challenging.

For instance with respect to the balancer pin as the TDC indicator, the OE system uses a Hall Effect detector, rather than sort of tap into and acquire that signal, and then translate it to some other usable form; it might be a better solution to instead create the signal directly in the form you need. One way might be to locate a stand alone detector/signal generator and swap it out for the OE sensor to do any testing, alternatively an add-on sensor/signal generator could be located in a different position say 180 degrees opposite the OE, you might fabricate a bracket that could easily attach to some hard reference points that would allow the sensor to be positioned correctly. The 180 phase difference could be accommodated electronically or through some other signal conditioning or the balancer could be drilled and tapped for a second pin that would be installed for testing purposes.

The signal could be generated through different technology also, instead of using Hall Effect technology; I think that because of the physical circumstance a photo-interrupter may be a good candidate. Photo interrupter modules incorporating an emitter and detector arraigned across a pre-defined gap are readily available. Something like that could detect the pin as it passes through the detector modules gap, again this could be mounted as a substitute or in an alternative location. Now the photo interrupter would probably be less than idea for a permanent installation because it would be susceptible to dirt degrading its operation, if one where mounted to a bracket which in turn could be held in a specific predetermined position maybe even by a couple strong magnets say, to be use only when doing testing it could work pretty neat!

Nowadays it should be relatively easy to find an IC that will drive the sensor and output an appropriate signal. Electronics have become to some extent modular building blocks, often times a sensor vendor will have exemplar compatible drive circuitry available in its application notes, and IC manufactures very often do the same showing their IC with a sensor and any related necessary components to generate specific outputs. National Semi- Conductor used to publish volumes of application date for the wide array of chips they offered. Today there are probably programmable micro processors with onboard A/D converters that can accomplish serious signal conditioning.

Just for fun check out STAMP and PIC micro-processors, in fact that is what techguy512 of this forum used to implement his programmable tach amp replacement.

Nowadays once the signal acquisition and waveform generation tasks are addressed it's only a short hop, skip and a jump to adding a Bluetooth interface and a Smartphone app where someone could watch what the engine was doing on there Smartphone as the drove along, and simultaneously record and archive that to compare over time!