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DT125R Forum -> CLOCKS -> Tachometer
Post Info TOPIC: Tachometer
Craig


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Tachometer
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Hello ,


I've recently bought a Yamaha DT125X.  It doesn't have a tachometer (rev counter) fitted as standard so I was thinking about making my own.  I'm guessing that some part of the bikes electronics outputs a signal which is related to the engines RPM.  Does anyone know if such a signal exists?  Has anyone got any information on this signal (i.e. where is it, how does it work)?


I'm thinking that the CDI unit might output a signal which I could use to determine the engines RPM?  Has anyone got any detailed information on the workings of the CDI unit?


Thanks ,


Craig.


EDIT


Now I think about it I suspose I could just connect something to the 12V signal going to the igntion coil?  I would have thought the RPM of the engine is directly related to the pulses going to the ignition coil?  So if the engine is going at 7000RPM then the igntion coil would be receiving 7000 pulses per minute


If all that is true then it wouldn't be that big a deal to make a digital display to show the engines RPM.



-- Edited by Craig at 19:32, 2006-03-11

-- Edited by Craig at 19:34, 2006-03-11

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r0bsk1


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Standard setup for a tacho is driven mechanicaly from the engine (clutch side) via a cable. If you could find the parts i bet u could mod your existing engine. Dont have my bike to hand and the mo to double check.


You're right, electronic tachos read the pulse to the spark plug. 1 spark = 1 RPM. I know such tachos exist as thats what many cars and bikes already use, its just a matter of sourcing the kit. Ill keep my eye open......



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2tScreamer


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Hi

As robski said you should be able to fit the tachometer gearbox from an older bike but then where would you put the big analogue tacho box.

There must be a aftermarket gadget somewhere that reads sparks from the HT lead with a digital display u can place somewhere

EDIT: http://cgi.ebay.co.uk/Tachometer-for-your-X-sport-Thumpstar-and-all-others_W0QQitemZ8044432161QQcategoryZ9946QQrdZ1QQcmdZViewItem

Bit pricey for what it is tho

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r0bsk1


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Hi Craig, any reason why you want to fit a tacho?

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wheelie


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as far as I know you can get digital ones that clip onto either the ht lead or of a cable from the cdi unit they go on ebay for around 50-100 quid but the ones ive seen have digital speedos in em as well so if you are thinking of digital may as well go the whole hog....


Also robski is right  BUT it doesnt mean that all the gearing required is in there i got a replacement engine and the tacho hole is blanked off and has no internal gearing....... :(


 


Jas


 


 



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Craig


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I think making a tacho which is connected to the ignition coil will be the easiest option.  Trying to make something that will connect to the actual engine will be more trouble that it's worth.  At the moment I'm really just looking for a simple solution.


I've got no real reason for wanting a tacho other than I thought it would be fun to make one.  I'll put the details on my website if it works.


For those of you who have an interest in electronics I'm planning on using an 8-bit microcontroller to do all the necessary processing and displaying of data.  If I could somehow connect the speedo to the microcontroller I could then also store the RPM and the speed in some memory attached to the microcontroller.  Then after a journey I could download that data from the microcontroller to my PC.  I could then display the RPM and speed during the journey in graph form on the PC.  Other data from the bike could also be stored in the microcontrollers memory which could maybe help with tuning the bike.


My background is in programming and electronics so I'm okay with that part.  My knowledge of bike mechanics is pretty weak though, so that's the bit I'm researching at the moment.


Cheers ,


Craig.



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wheelie


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Mmmm interesting m8 ive got no rev counter on my tdr lol if yours works let me know i might be interested in an lcd one if ya can make em


can you make lcd back lit temp displays ??? id be interested in that as well


Jas



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r0bsk1


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Craig wrote:

For those of you who have an interest in electronics I'm planning on using an 8-bit microcontroller to do all the necessary processing and displaying of data.  If I could somehow connect the speedo to the microcontroller I could then also store the RPM and the speed in some memory attached to the microcontroller.  Then after a journey I could download that data from the microcontroller to my PC.  I could then display the RPM and speed during the journey in graph form on the PC.  Other data from the bike could also be stored in the microcontrollers memory which could maybe help with tuning the bike.
A datalogger....liking the sound of that! How about telemetry too That'd fit my RC helicopter too

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2tScreamer


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Craig wrote:

For those of you who have an interest in electronics I'm planning on using an 8-bit microcontroller to do all the necessary processing and displaying of data.  If I could somehow connect the speedo to the microcontroller I could then also store the RPM and the speed in some memory attached to the microcontroller.  Then after a journey I could download that data from the microcontroller to my PC.  I could then display the RPM and speed during the journey in graph form on the PC.  Other data from the bike could also be stored in the microcontrollers memory which could maybe help with tuning the bike.


If you make this and it works, I'd pay good money for one for my project bike.

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