Square Wave Multiplier

[DangerStevie]

Hey all, i have an issue with my fireblade and i would like to pick the brains of any resident electronics experts.
My blade speedo sender give a 5v 1:1 square wave signal to the std speedo, i have fitted later clocks which expect 1:4 5v sq wave signal. Does anyone know any good reading material or suggest a way i can multiply the standard 1:1 wave to create the 4:1 waves?

Cheers

 

[zx9]

I assume you have looked at changing the sensor and or rotor for ones that suit the new speedo head or is this a non starter due to different wheel or spindle size?

 

[DangerStevie]

The speedo drive on my engine is taken off the chain sprocket and is 1 pulse every 360 degrees, the one the speedo is expecting is 4 pulses every 360 degrees and is usually taken from a trigger wheel on the later cranks from the sensor mounted in the top of the gearbox and i cant retrofit the later sensor to my bike. So yeah the easy possibilities have been looked at. I could always change the clocks for the original ones but wheres the fun in that?
I think i need to build an adjustable frequency square wave generator that uses the original square wave from my existing sensor as a trigger to begin its count. But if i am honest i am not 100% sure where to begin.
I have found a product called the speedohealer that can do the job but i resent buying anything i can make myself.

I can forsee a few hiccups though - The problem with using the original pulse as a trigger is the circuit could only ever know the duration for the 4 pulses by sampling from the trigger. So in effect it would send its signals every other trigger. So i think that would cause lag and jumping at the speedo.

 

[rich r]

I'd probably use the venerable 4046 phase locked loop ic to do the frequency multiplication, assuming the frequencies required are within it's range. It's been around for over 20 years, and is commonly used in digital electronics to double frequencies.

Do a web search and you'll find datasheets and hundreds of circuits using them.

Though it might be easier in the long run just to relocate the sensor, alter the trigger wheel, or fit the other speedo!

 

[Pete.]

I assume you have looked at changing the sensor and or rotor for ones that suit the new speedo head or is this a non starter due to different wheel or spindle size?

EDITED:

This is the easiest solution. Since your sprocket provides the pulses you need to make a washer to go under the sprocket nut to provide four pulses. I could make you one at the weekend.

How about a pic?

 

[tigler]

Just to be clear, is it actual signal ratio you are talking about, or frequency ?
I read it as a 1:1 versus a 1:4 RATIO. This implies the pulse period or width is 4 times the pulse amplitude ?

 

[R Kraft]

I like the cd4046 for a circuit like that ,but a couple of these might do the job.:http://www.radiolocman.com/shem/shem-cache.html?di=11144
Robert

 

[DangerStevie]

by 1:1 i mean the standard sensor i have fitted provides 1 pulse per 360 degrees and the clocks are expecting 4 pulses every 360 degrees (4:1).

The sensor fitted to my bike i believe slots over the sprocket nut and spins with it from what i have been told, but i can check that later and ill draw it all up on solidworks to see if i can retro fit the later hall sensor and use a profiles washer like you suggest as that was my original preferred solution.

 

[tigler]

Ok, thats frequency not ratio. A PIC microcontroller could be used to convert the pulse count.

 

[DangerStevie]

ah sorry, pardon my ignorance , would the pic still give an issue with lag? due to it having to sample the frequency of the pulses before any calculations could be made?

 

[tigler]

Not that you would notice.

 

[rich r]

I considered using a PIC, but it's a bit overkill when a cheap PLL would do the job. Depends how quickly you could knock up the code I suppose though.

My preferred option would still be to change the sensor/trigger arrangement and not rely on having something to invent three pulses per cycle...

 

[DangerStevie]

Inventing 3 pulses per cycle is not so bad, and if you make it adjustable you could take up error from changing sprockets etc.

tigler, can you point me in the right direction for what kind of controller/circuit & programming i should be looking at?

 

[tigler]

It's quite involved to go into detail here so have a look at this site :-

http://www.microcontrollercentral.com/?cid=goog

 

[the snooper]

the problem i see using a circuit to generate 4 pulses per 360 degrees is how is the time between the 4 pulses going to be changed with the increase and decrease of speed, ie if you use the original pulse to trigger four its going to fire all four at at the same speed and if you suddeny increase the speed of the bike it wont have finished the previous set of pulses, they way its supposed to be is that the frequency of the pulses increase with the speed of the bike

 

[Windy Miller]

the problem i see using a circuit to generate 4 pulses per 360 degrees is how is the time between the 4 pulses going to be changed with the increase and decrease of speed, ie if you use the original pulse to trigger four its going to fire all four at at the same speed and if you suddeny increase the speed of the bike it wont have finished the previous set of pulses, they way its supposed to be is that the frequency of the pulses increase with the speed of the bike

It's only a Fireblade, so it won't pick up speed that fast!

Joking really - the Fireblade is a cracking bike- even the old ones are mental!

 

[Robotstar5]

Joking really - the Fireblade is a cracking bike- even the old ones are mental!

Got a reputation as "the widowmaker" when it first launched

 

[tigler]

Thats a common thing for Honda's ! Some Kawasaki's weren't too clever either !

 

[Robotstar5]

Thats a common thing for Honda's ! Some Kawasaki's weren't too clever either !

I remember the "rubber framed" H1's, mach III's etc.!

 

[mike 109444]

Surrly if the pickup is a hall effect device you could just add 3 more magnets at 90 degrees to each other = 4 pulses per revoloution of the sprocket.