Electronics on race bike.

[Shaun691]

Hi,

I need some help with the electronics on my race bike (motorcycle).

After a race I download the recorded data from the computer on the bike to a PC. The data is viewed in graph format on the PC so the performance can be seen and changes made to the bike to make it faster. Recorded channels include engine speed, rear wheel speed, fuel pressure, oil pressure and many more.

Trouble is I can wire up each gear to the onboard computer so I can record the gear shift points but I do not know the electronic parts I need to do it. I have a 12v solenoid for each gear and the computer can recognise each gear with a different voltage level. So my question is 'what inline parts do I need that will have a fixed voltage value between 0v and 12v that I can set up to solve my problem'. The inline part will fit between the 12v solenoid and the onboard computer so when a particular gear is engaged the computer will recognise the incoming voltage and assign it to a particular gear.

Thanks for your help,
Shaun.

 

[(*steve*)]

Does the solenoid remain active while the gear is engaged, or does it only become active momentarily when the gear is selected?

Either way, the same trick may work...

From each relay, set up a resistive divider that generates a distinct voltage for each gear. Use a diode from each to connect to a common point where the voltage will be measured. Only the highest voltage will be seen at this point (which won't matter unless you can somehow select more than 1 gear at a time).

If the solenoids are only activated momentarily you will see a voltage appear when the gear is selected. If the solenoids are continuously powered while the gear is selected. the voltage for that gear will remain until (presumably) another gear is selected.

This signal may be quite noisy, but I suspect that that also applies to other signals you record and your hardware/software is capable of making sense of it.

 

[Shaun691]

There is a +12v feed for each gear, it is not momentary.

Voltage divider is the term I was looking for. I have done some research on the web this afternoon and understand enough to get the system to work I think, thank you for posting the info it was exactly what I was looking for.

There was some good examples on youtube and wikipedia was helpful to.

Do you think the diodes are critical? I have microswitchs feeding the gearbox solenoids so if I take the +12v feed from the microswitchs there will be no back feed to the others because the circuit in them will be broken because they are switched off?

 

[(*steve*)]

It can be done without diodes, but the problem you will face is that the output of the currently active voltage divider will be loaded down by the other (unpowered) voltage dividers.

With a bit of skill you can actually take advantage of this, but you'll need to be more specific about the way the solenoids are switched and their DC resistance.

Using diodes is simpler to get working and since we're helping at a distance, it's the approach I suggested.

 

[Shaun691]

I understand, thanks for your help.

I had a play around yesterday with some resistors, multimeter and battery, I can see the principle of how it works and figured out the diode thing after posting!

 

[Shaun691]

Steve, I have another question.

I have built the voltage dividers, I have 3.1v, 6.7v and 9.3v circuits 1 for each gear.

With the resistor pack I also brought a diode pack. I fitted a diode in the correct place on one of the circuits and saw the correct voltage output, when I turned round the diode I still saw voltage but it was slightly lower. If diodes are '1 way electronic valves' surely I should not be able to see voltage through the diode in 1 direction

 

[(*steve*)]

Diodes have a small voltage drop that depends on the current flowing through them.

For many purposes it can be considered 0.6V.

You will then expect 2.5, 6.1, and 8.7 volts.

If your logger just records the voltage, you'll be fine. If it wants to interpret the voltage, you may need to test to see what the voltage actually is. Note that because you're using a resistive divider, the voltages will go up and down with the battery voltage too.