Good morning lads. As you most likely know i am upgrading my bec to a ZX12R.
Its nearly finished and I had to let my joy out somewhere as the missus thinks ‘yeh that’s great’ in a sarcastic way when I told her the good news.
Last night I plugged in the battery to see if my wiring had worked or created a nice new garage heater and smoke machine. Well I can happily say it
went well, I have fitted the Efi LED to my dash and it works as expected, 2 seconds lit with the fuel pump working, then both turn off until I turn
the key to start the car. I haven’t got the started connected yet but the relay clicked on so i am now reasonable happy its all ok to start.
But there is one bit of wiring left to do, its either a 10 minute job or a few weeks work if I cant suss it and I have posted a few questions on here
about it before.
Instead of using the 3 separate sensors to feed my clock speedo, Digi 8 gear indicator and my digital speedo i want to try and use the one that’s
fitted to the ZX12 engine. But i am unsure if I can use it and have a few questions regarding it.
With different types of sensors and outputs i am trying to see if the 3 devices I have can use any type of input. Luckily they all say they can be
connected upto an existing speed sensor fitted to the car/bike. But for a reason I can’t work out you have to fit a resistor across the sensors power
and output signals. Why is this? The digital speedo (motoscope mini) comes with a 2.2k resistor for this, but looking at the bikes workshop manual for
testing the sensor it suggests fitting a 10k resistor. Does it matter if I fit either, would the wrong one damage the device or give a false
reading?
What I am asking is what is the reason for the resistor and what effect different values will give on the output?
Cheers
Andy
with the engine now in a car and gear ratio now totally different to that from the bike. How are you going to calibrate the speedo? assuming that you were saying the bike engine has a such a speedo output
The digital speedo and gear indicator learn the pulse ratio at a given speed so basically you drive at 31mph (For the minscope) using gps or following
another car and it then records this and works out the other speeds. Worked really well the first time i did it and only needed about 10 seconds of
driving.
The 'normal' speedo is a different matter, its got loads of dip switches on the back and you have to work it all out yourself. Once i have
it working with the other devices i will see how many signal outputs the bike speed sensor outputs per revolution of the prop, then with the known
gear ratios, diff and wheel and tyre sizes i should be able to work it out. I can then check it against the digital one.
[Edited on 9/1/09 by Moorron]
quote:
Originally posted by Moorron
But for a reason I can’t work out you have to fit a resistor across the sensors power and output signals. Why is this?
often the devices come with what is called "open collector" driver - namely a transistor that is left open circuit. It requires a resistor to be connected to the output and other end to power. This way, the output is pulled high (to power voltage) when the transistor is off and pulled low ( 0 V or as near as) when transistor is on.
The digital speedo (motoscope mini) comes with a 2.2k resistor for this, but looking at the bikes workshop manual for testing the sensor it suggests fitting a 10k resistor. Does it matter if I fit either, would the wrong one damage the device or give a false reading?
from above, you select a resistor that will give the above voltages but is not so low that the current would exceed the transistor's max. Without knowing the spec. I'd say any value from 1 k to 50 k would probably work. Bear in mind that the input resistance of the device (speedo) that is being driven, if low - it shouldn't be, would affect the cricuit hence you would go for a lower value. Try it with the 10 k, then 5 k then 2.2 K in that order. Measure the ouptut voltage with the speedo connected for both high and low values and that will show if the sensor will supply the correct voltage to the speedo. If you choose too low value of resistor, e.g. 100 ohm, then may find the current is too much for the transistor and it may go pop.
Great reply there, i will give it a go and see what voltages i get. One thing i want to do is power all 3 devices from the bike sensor. Will i likley
overcook it with all 3 hanging off the one wire or are the resistances of the devices generally low? Either way if the sensor goes pop atleast i can
replace it or just give up and make an adaptor between the prop and sprocket to house some magnets.
Cheers.