Diesel tachometer

[Sibbo]

This tachometer is on Ebay here .http://www.ebay.com.au/itm/Tachometer-8 ... 256819ff5d

This is the blurb, can anyone tell me if this can be rigged to a Chinese 10 hp Yanmar clone ,
''Description: This Tachometer IS ALTERNATOR DRIVEN and is for Diesel engines.
86mm gauge, stainless steel bezel, white dial , perimeter lit, 0-4000rpm range.
This can be programmed for 3 to 155 pulses per engine revolution. Detailed calibration instructions will be provided along with the product.

Also available with a black - please check our listing "Tachometer 86mm Diesel (Black Dial)"
* Brand NEW product
* One year warranty (pl refer to our warranty statement below) ''

[alexanderfoti]

I don't see how it can be alternator driven (IE ac voltage driven) and then state it can be programmed for pulses, unless it does both!

IF its pluses driven, it could be rigged up using a proximity sensor, which is what I am currently trying to accomplish.

[andrewaust]

Sibbo, I'd ask the guys a lot of questions, it seems as if it would pick up on a sensor, but they offer no real idea of it needing a multiple magnetic or just photo sensitive pickups.

A

[Eddy Wane]

I notice that this topic is quite old but one method of getting a pulse to run a tacho would be to use an ABS type of sensor fitted near to the starter ring. These units are quite robust and relatively easy to mount.
The ABS sensor on modern cars not only controls the brakes but its signals on some cars are also used for the speedometer and as a tachometer is a similar type of instrument it should work fine. As the teeth pass the sensor a pulse is generated this should be easy to programme into the tacho unit as the number of teeth will be known. e.g. 100 tooth starter ring, 1 rpm = 100 pulses etc.
The electronics side should be able to handle the amount of pules generated and there are pulse divider circuits available to reduce the count if there are too many pulses for the tacho unit to process.
I sometimes use the ABS sensor when I fit taximeters if a conventional speed pulse is not available on a vehicle.
There are also other car sensors (crankshaft position sensor) which may do a similar job.

[henneberg]

The ABS sensor is an option and might give a better defined electrical signal, compared to the generator AC signal.

I have used one of these rev. counters: http://www.ebay.de/itm/271664328045

I made a small road trip video with the rev. counter: http://www.youtube.com/watch?v=b4UsIn5QLxk

The rev.counter can easily be programmed to fit the actual sensor/generator frequency.

For the sensor signal, I used Ruggerini MD151 generator output, but a small signal shape / conditioner electronics was needed to be designed:

[Eddy Wane]

Erik.
I know that vehicle instruments are not that accurate unless it is officially calibrated but it is nice to have a rock steady needle on revs or speed. Looking at your video the clocks you have fitted are very nice and look robust.
Eddy.

[alexanderfoti]

I ended up buying this:

http://www.ebay.co.uk/itm/Rev-counter-0 ... true&rt=nc

It was adjustable to run of a alternator ac signal, or 4, 6 or 8 cylinder petrol engines.

I supply it with a pulse from a proximity sensor and have 2 magnets mounted to my engine pulley.

I have calibrated mine with an optical tachometer I have.

[henneberg]

Hi Eddy,

For the particular rev.counter, I made a precise test (magnet, hall sensor + oscilloscope ) rpm on the engine, and the rev. counter fits within +/- 50 rpm.

Perhaps I was lucky with the manufactures calibration

[gearhead1951]

Check out www.dakotadigital.com

[Anorak_ian]

Check out http://www.dakotadigital.com

Thanks but way too expensive.

[gearhead1951]

OK , they aint cheap and maybe someone here can find you a more economical choice !

I have been told by a good few folks this little gem , "If you caint afford to do it right the first time then what makes you think you can afford to go back and redo it 'cause yer first bodge failed ?"

[Anorak_ian]

OK , they aint cheap and maybe someone here can find you a more economical choice !

I have been told by a good few folks this little gem , "If you caint afford to do it right the first time then what makes you think you can afford to go back and redo it 'cause yer first bodge failed ?"

I have built a diesel bike from scratch, it would not have been built if I had your outlook on life.

A good few folks don't even know how to change a three pin plug.

Maybe you "bodge" things but I draw on sound mechanical experience, trial and error and experimentation.

[alexanderfoti]

I have this lying about if you can drive it somehow. I used to drive it from the fins on the flywheel. (28 teeth compared to the 30 that its looking for)

A proximity sensor will acomplish that easily.

Forgot the bloody link!

http://www.ebay.co.uk/itm/171114230020? ... 1560.l2649

[coachgeo]

I have this lying about if you can drive it somehow. I used to drive it from the fins on the flywheel. (28 teeth compared to the 30 that its looking for)

A proximity sensor will acomplish that easily.

... link!

http://www.ebay.co.uk/itm/171114230020? ... 1560.l2649

For when that ebay add is gone forever......... here is the info

Teleflex Marine Diesel Tachometer

0-4000RPM

Designed to use a 30tooth magnetic pickup.

Backlit and integrated hour meter (currently reading 54)

[coachgeo]

I have this lying about if you can drive it somehow. I used to drive it from the fins on the flywheel. (28 teeth compared to the 30 that its looking for)

A proximity sensor will acomplish that easily. ...

Have you not; or someone else explained how to use proximity sensor for this another thread? Vaguely remember that being the case. If anyone recalls the thread please post up the link. Would be good place for it.

[coachgeo]

The ABS sensor is an option and might give a better defined electrical signal, compared to the generator AC signal.

I have used one of these rev. counters: http://www.ebay.de/itm/271237251141....

The rev.counter can easily be programmed to fit the actual sensor/generator frequency.

For the sensor signal, I used Ruggerini MD151 generator output, but a small signal shape / conditioner electronics was needed to be designed:

Schematic.jpg

Again so we don't loose needed info when this ebay add ends...... here is the info on the tach henneberg refers too.

KUS Drehzahlmesser analog bis 4000 RPM und Betriebsstundenzähler LCD, Edelstahllünette in ansprechender Optik

- geeignet für Diesel-und Benzinmotoren, 2- und 4-Takt Motoren (Dieselmotoren benötigen Klemme W an der Lima)
- hochwertige Ausführung des Erstausrüsters KUS, baugleich WEMA, für den Bootsport konzipiert und hergestellt
- technische Daten ( siehe auch Foto 2 unsere Angebotes )

Einbaudurchmesser 85 mm, Mindesteinbautiefe 55 mm, verwendbar für 12 und 24 Volt

Staub- und Wassergeschützt nach IP67, für den Bootsport ausgezeichnet geeignet

Einstellungsintervall: 0-255

Wahlweise rotes oder gelbes Licht, excellente Anti-Beschlag Eigenschaften, gebogenes Glas, sehr edele Optik

Mit Einbauanleitung ( englisch ), Kabelverbindung

DMT Artikelnummer: K-Y07008

Technik-Hotline: +49(0)175-2446492 Versand-Hotline: +49(0)151-58556504

[alexanderfoti]

I have this lying about if you can drive it somehow. I used to drive it from the fins on the flywheel. (28 teeth compared to the 30 that its looking for)

A proximity sensor will acomplish that easily. ...

Have you not; or someone else explained how to use proximity sensor for this another thread? Vaguely remember that being the case. If anyone recalls the thread please post up the link. Would be good place for it.

I dont belive so, but somebody had given me some info on how to use it with a visible segment wheel.

With a Proximity sensor its easy to wire into the the signal wire and then to ground, it just acts as a switch on/off when it comes near metal.

[sbrumby]

There has been a lot of talk on this subject, mine works perfect, it is the original rev counter (electric) for the bike, it was a 4 cylinder bike with only two coils giving out dummy sparks. Basically only one coil was connected to the rev counter, so on my bike the key that holds the pulley on the crankshaft signals the proximity sensor. Basically takes less time to fit than it takes to write this post.

[gearhead1951]

OK , they aint cheap and maybe someone here can find you a more economical choice !

I have been told by a good few folks this little gem , "If you caint afford to do it right the first time then what makes you think you can afford to go back and redo it 'cause yer first bodge failed ?"

I have built a diesel bike from scratch, it would not have been built if I had your outlook on life.

A good few folks don't even know how to change a three pin plug.

Maybe you "bodge" things but I draw on sound mechanical experience, trial and error and experimentation.

For 20 years I was a main propulsion diesel engineer in the us navy , if you are capable of designing a Tach drive that works from scratch more power to you !
I am aware of a few sources for parts that would allow you to create a such a thing (radio shack or tandy ect...) and I was addressing those without the technical skills or the desire to learn them ! Actually it just occured to me that you might even be able to scavenge something usefull from a diesel car in a scrapyard !

Otherwise dakota digital and other vendors are your best choice !!

[dieseltech]

OK, so first of all: yes I have checked the date on this thread. But due to the nature of the problem, I think it will benefit the general public for me to post this here:

In the "ancient" times, when the alternator voltage regulator was the most complicated electronic device present on a diesel engine (>20 years ago!), many diesel cars had RPM gauges. How was it done?

Some more expensive cars (ie. the W124 diesel) used an approach similar to what has been suggested earlier in this thread - a magnetic pickup from a toothed ring, in that case the flywheel ring gear (it was needed for the anti-jerk module anyway). Special circuitry was required to convert that into a series of pulses that imitated the ignition coil signal for a typical gasser tach.

Of course nowadays the "special circuitry" can be built for $5 using commonly available electronic components, but you still need to know how to do that, and it can be nontrivial if you don't know what you're doing.

However, that was the minority approach - it was normally disfavored because it involved adding extra components. That's bad because it adds complexity, weight and costs $$$.

There is another minority approach available nowadays - the clip-on transducers that are installed on the metal injection pipes, normally used only in aftermarket installations. But they have their own shortcomings, including high cost.

Now, a diesel doesn't have an ignition coil or anything else that produces electrical pulses with a frequency dependent on engine RPMs... or does it?

As it turns out (no pun intended), the alternator on a diesel engine is an AC generator. Since it is driven by the crankshaft, the output frequency is proportional to engine RPMs (there is a slight error if belt driven but still less than 1%).
Even better, the signal is extremely strong - it swings from about -1V to about +15V, and is very close to a squarewave, due to the specific electromechanical nature of the alternator.
A standard car alternator puts out 6 pulses for 1 turn of the shaft, so just multiply this times the drive ratio and you have the # of pulses per 1 turn of crankshaft. You can handle it from there.

BUT there is a catch... this only works on field-regulated alternators - ie. those used in cars and trucks; it will not work with the permanent-magnet, output-regulated types normally found in bikes and yanclone diesels - the regulator chops up the output waveform and the resulting signal has little to do with RPMs.

99% of old diesel cars with RPM gauges used this approach. It is extremely simple - just one wire from the "W" terminal (phase output, exists just for this purpose) on the alternator to the gauge itself. And cheap - again, just one wire, no extra hardware. The gauges themselves were just factory-modified gasser gauges, altered to account for having over 10 pulses per crankshaft revolution instead of 2 as in gassers.

Even if your alternator has no "W" (phase) terminal available, it is a very simple modification to attach a wire to one of the 3 phase connections inside the alternator itself, which does exactly the same thing. And then you can use a stock gauge from a diesel car, or an aftermarket tach that was also designed to work that way. Or homebrew your own, if you can handle electronics.

But again, that won't work on permanent-magnet (stator) generators. So if you are building a bike that uses a car alternator, you are lucky. If using a yanclone, not so much. ABS sensors and rings, anyone?

Finally, there is one trick you can use with the ABS approach: the output voltage of a standard inductive ABS sensor (2 wires, no power supply, has built in magnet) is directly proportional to the sensor ring RPMs, as long as you don't put any electrical load on it. So if you hooked up a good AC voltmeter - one with a very high input impedance and capable of handling frequencies into the kHz range - the readout would be proportional to RPMs, differing by a scale factor.

Unfortunately I'm not aware of any off-the-shelf voltmeters that would be directly suitable for this - you would need to homebrew an adapter circuit that would convert that signal into a DC voltage, ie. 1V per 1000RPM - and then feed that into a standard DC voltmeter. Such circuitry would be very simple and require only a couple of components at its simplest.

[tappy]

One can buy "frequency to voltage converter" microchips - typically LM2917 for about 60p from places like Maplin, and with minimal other components convert an oscillating signal into a voltage which increased with the frequency of the oscillating signal.

Used on engines they can be a bit wobbly or laggy if you just use a "once per rev" signal, but if using a 6-per rev signal from an alternator they're pretty effective.

Incidentally, a few years ago I successfully took a tapping from the alternator on my GS500 to measure revs - a permanent magnet, solid state reg/rec type. I took it from one of the 3 yellow wires before they got to the regulator. Given the voltages involved I sent this signal into a buffer and a schmidt trigger but it worked quite effectively.

I can't recall if I took the signal across a phase (using 2 of the yellow wires) or from a single wire to earth, but like I say it seemed to work OK. I also stuck an oscilloscope on the raw signal and unsurprisingly the wave was a "clipped" sine wave. I suspect the schmidt trigger would have helped at high alternator loads when the reg/rec would be doing less clipping..

If anyone's curious I might go see if it works on my current bike...

[Anorak_ian]

Nar, not realy.

Lol

All you need is some ordinary household bleach, an empty detergent bottle and some sticky back plastic

[sbrumby]

Iam with Ian on that one.

[tappy]

*Puts feet up*