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With a view to possibly rigging up an Arduino microprocessor based shift light or even rev limiter (yes I know they don't really need one) I was having a prod about the project bike with a multimeter.

50v AC from the tacho connection on the transducers, does that sound about right?

1500 mV AV direct from a red pickup connection but connecting the multimeter significantly slowed the idle, so hooking in to that doesn';t seem like a good strategy for best performance.

I could possibly go down the Scitsu tacho induction from an HT lead route but my electronics knowledge isn't up to it.

Essentially I need to provide a stream of maximum 5v DC blips to feed an Arduino analogue input pin. The rest is just a matter of some C code, resistors and LEDs.

Anyone tried anything like this?

I can probably get away with calibrated seat of the pants to take it to 9000 or so, but the lad is used to rev limiters (not even a bike with a tacho) .On hill climb gearing he might get in to valve bounce territory, if the red mist sets in and he is within a tenth of a points position.

Sounds like fun! I think I'd go for the tacho output from the transducers, suitably potted down with a couple of resistors. I don't know what the waveform is like coming out of there, it might need a bit of cleaning up.

72degrees wrote:... if the red mist sets in and he is within a tenth of a points position.

I think I'd go with the red mist...

penman wrote:Sounds like fun! I think I'd go for the tacho output from the transducers, suitably potted down with a couple of resistors. I don't know what the waveform is like coming out of there, it might need a bit of cleaning up.

Several different strategies have been suggested to me by people who know more about this kind of thing than I do.

The simplest (though it sounds far too easy to work to me!) is just a hall effect sensor taped in line on a HT lead. The Arduino has a pull up resistor built in to the analogue input so allegedly the sensor output of 5v DC blips can be just plugged straight in. Think it best I try it just at kickstart speed first though.

The tacho output would be very convenient but the Arduino analogue input is max 5v and DC only so it seems it would need rectification as well as a drop in voltage. Certainly doable with a simple diode and resistor circuit.

As you say, the first job is to see if I can investigate the wave form. I've already created a crude oscilloscope using the Arduino and displaying the curves on a laptop using VBNet (example code came with the Arduino kit). It will pick up mains hum very well without a physical connection (just on a length of wire 'aerial' into an analogue pin) so I might see what it picks up close to the bike. I suspect it will reveal a very messy signal indeed that way - though the non-functioning lighting coils may be help!

A few turns of wire around an unused pole on the alternator would provide a low voltage signal easy to convert to TTL levels.

EVguru wrote:A few turns of wire around an unused pole on the alternator would provide a low voltage signal easy to convert to TTL levels.

That's an interesting idea. Unused as in just not connected, or would at least that lighting coil have to be unwound? I'm attracted by the minimalist additional circuitry strategy of the hall effect sensor approach. Apparently it might be possible to tap directly in to the pickup signal using an op-amp as a buffer/voltage follower - high impedance input to avoid sucking current away. Tricky to get working reliably with just a simple, single power supply though it seems.

The beauty of the hall effect approach is that with the right one (TEXAS INSTRUMENTS DRV5033AJQLPG has been suggested) a simple PP3 dry cell can power the sensor and the Arduino. It won't have to operate for sustained periods. If I go for something bigger and brighter than single LEDs it will need a 5v relay module and possibly something with a bit more than capacity but that's a long way off yet.

You could probably use one or two coils, rectify the output and feed the raw DC to an Arduino input. Put another diode in line and that could go to a smoothing cap and you've got a supply for the Arduino.

EVguru wrote:You could probably use one or two coils, rectify the output and feed the raw DC to an Arduino input. Put another diode in line and that could go to a smoothing cap and you've got a supply for the Arduino.

Food for thought.

Getting the ignition tip top takes precedence. I need to experiment with removing the resistance from 5K ohm caps. It has brown NGK 90 degree (no resistor) ones now which must have been put on not that long ago, but the front one pokes out in to the breeze and spray from the front mudguard a bit too much for my liking. As I have a spare NLM ignition module I might also rig up mountings for that and a pair of 'performance' coils.

Resurrecting an old thread I know but...

My tacho doesn't work, actually it never has!
It's fed with a signal by a small PCB which is conncted to where the pickup feeds into the transducer because - you guessed it - my transducers are the grey ones without a tacho output.

I've checked the tacho itself and it reads perfectly with an pulsed input of 10V or more. I assume that's 'normal' as it would usually see a 12V signal ?

Hanging a scope onto the transducer input shows it is getting 2.4V pulses from the pickup at idle. Having read through old ignition realted threads people have measured around 0.4V with a multimeter when kicking the bike over but I didn't see a value with the engine running. So here's what it looks like for future reference

Ignore the readings on the right hand side, they relate to the live input not the stored waveform


On the basis that as the bike runs perfectly well it's the signal interface that's playing up and needs replacing - can anyone recommend one?

I found this circuit when I was considering an alternative. Haven't tried it, though.
http://www.motomoriniclub.nl/REVcounteradapter.pdf

I have a widget for electronic rev counters, but I do not have an electronic rev counter - only chronometric ones are good enough for me.

Nerd alert...

I do not have a revolution counter as I do not need to know the total revolutions my crankshaft has done. I do have a tachometer as I need to know the current revolutions per minute of the crankshaft. Taken from my father's pre war engineering books...

I hate the use of rev counter, but maybe the old man's books are incorrect? Please enlighten me!

And your point is or should one use revolution counter rather than tachometer ? If you go onto the AC Forum there is presently a huge debate about terminology i.e. gear shift lever or speed change lever, depending on which side of the Atlantic you live, oops sorry pond. Or. perhaps you do not know the difference between tachometer and a electronic or magnetic revolution counter or crank speed indicator if one wishes to be pedantic. After all, who is interested in counting revolutions when only the speed is required?

My point is what is the correct name. Have I been correct to not use rev counter for tachometer?

Simple question for the general populace.

OK, I'm in for a laugh.
Tachometer means (literally) speed-measurer (for the Greek geeks).
Rev. Counter (actually revolution-counter) means what it says, ie it is a device for counting the number of revolutions of a shaft.
Though both have now come to have the same meaning (in common parlance ), I think both are incorrect, the correct term being Revolutions Per Minute (RPM) gauge.
But there again, who really needs one?