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need some clarification for LED Tachometer

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steev

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hello all,
first of all sorry for asking help in this project as it has been already asked .but i coudn't resist.i searched the forum lot of times but most of the tachometers are for CARS and they were not clear.i want to built one for my bike.i did a small search over net and found this ckt. **broken link removed**
this is exactly suited for me.
every thing is ok except the input for the circuit.its given coil -ve lead in the ckt.i know input for this ckt is pulses from the spark plug.but how to get them? can i directly connect the spark plug output to the ckt....this dosen't feel good to me,spark means thousands of volts.
iam stuk at this place.
pls help me.

**below attachment shows my idea of placing LEDs arround the speedometer.
 

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You have a bike with a sparkplug??
Do you sit on the sparkplug?? Is it fun to pedal and to get zapped??

An ignition coil for a motorcycle has low voltage wires for the breaker points and a high voltage wire for the sparkplug. The tachometer connects to the low voltage side.
 
audioguru said:
You have a bike with a sparkplug??
Do you sit on the sparkplug?? Is it fun to pedal and to get zapped??

An ignition coil for a motorcycle has low voltage wires for the breaker points and a high voltage wire for the sparkplug. The tachometer connects to the low voltage side.

You're in the wrong century Audioguru! - motorbikes had point-less electronic ignition systems before cars did!.
 
Nigel Goodwin said:
You're in the wrong century Audioguru!
I have never had a motorcycle.
I see and hear very old guys riding very old Harley Davidson motorcycles and the guys and the motorcycles both probably have breaker points.
 
ooops wrong sentense used.imean motorcycle.here we call bike insted of motorcycle(and bicycle insted of bike) i hope u understand.

and in sparkplug spark jumps from electrode to ground.so u want me to take that ground right.pls correct me if iam wrong.
i'll try this and i wana know if there r more methodes.
thanks
 
Just connect the input of the tachometer to the switched-to-ground terminal of the ignition coil. The switch I show is a breaker point but your motorcycle might have a transistor as a switch.
Does your motorcycle have a negative ground?
 

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my motorcycle uses 12v battery.so i think it has -ve ground.iam uploading my bike spec. picture have a look.
**broken link removed**
 
Your motorcycle has an engine only a little larger than my cheap lawn mower.
It has CD ignition so my sketch will not be the same.
Doesn't the motorcycle already have a tachometer and you can use its input connection?
 
no theres no input connection for tachometer.thats why i want to make one by tapping the sparkplug.so which method u think is better
inductive pickup of pulse from the sparkplug wire
or by connecting the ckt to sparkplug ground wire

**yes it is a simple motorcycle launched by HONDA.it is enough for my daily use
 
Last week I talked to a guy who travelled across North America on his very big Honda Gullwing motorcycle. It is so big and heavy that it uses its starter motor to move it in reverse. Its 6 cylinder engine is bigger than the engine in my car.
 
The sketch shows the blue wire connecting to the orange wire. It doesn't show what those wires do.
 
We don't know if the CDI circuit pulses the GND or the +12V primary wire of the ignition coil. Probably the ground wire but you must find out which ground wire.
 
well is there any method to know which one(the ground or the +12v) pulses.i know using Oscilloscope we can get clear picture of pulses.but i don't have it.so is it possible to know by some method that atleast its pulsing...
 
Use an AC voltmeter on the low tension side. Just make sure the AC voltmeter reads 0Vac when only DC is on it. If not, you'll have to couple it through a capacitor.
 
i dono much abt motorcycle electric sytem.but u said AC voltmeter on low tension side.that means input to the ignition coil.which supposed to be DC.as we use 12v battery for the motorcycle.
 
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