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Motorcycle Gearshift Circuits

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Simple_One

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Hi All,

I've got two little projects I'm contemplating for my motorcycle:

Gear position indicator:
The motorcycle actually has a factory sensor for this, but it doesn't display anywhere (must just be used as an input to the ECU for something). As such, I'm not quite sure how to tap into this existing sensor and turn it into a display as the sensor works by having vastly different resistance readings depending on which gear is selected. Is it likely that it determines the gear position by applying a known voltage and then measuring the voltage drop?
In general, how would I start going about integrating the existing sensor into a circuit that displays a number or letter (N, 1, 2, 3, 4, 5, 6)?

Quickshifter:
For this I actually have a strain gauge sensor that is used to detect the pressure being applied to the shifter to change gear. Additionally the fuel control module installed on the bike already has a fuel cut 'quick shifter' capability - you just need to have a momentarily closed switch to short the two terminals in order to activate it. I'm thinking that a solid state relay is the key bit I would need for this....but in general, how would I go about designing a circuit that allows me to close the path of those two terminals, based on an input voltage from the strain gauge sensor?

In both cases, I'd like to use a circuit that has elements that are as robust as possible in terms of their exposure to vibration and elements, so I'm assuming solid state is what I should be thinking of...
 
Do you have a wiring diagram for your bike that shows the interconnection of the sensor to the ECU?
 
Yes I do. Standby and I'll try and grab an image and link it.

EDIT: The relevant sensor for gear position is 'GPS', number 20. The quickshifter stuff is aftermarket and not shown on here.
**broken link removed**

Key:
**broken link removed**
 
Last edited:
That is not quite what I expected to see. I expected the GPS (20) to have two wires coming out of it, one of which is connected to frame.

Try this: use a multimeter in DC volts mode. Measure the voltage at wire V (pin 2 of the ECU) and frame ground as you shift into various gears. Note the voltages and report back.
 
Will do thanks Mike, I'll get back with the voltages.

Here's the detail on the factory sensor. I happen to know that those resistances are not actually listed correctly since I checked it all with the DMM and the order shown there is wrong, but never the less, gives some idea.
**broken link removed**
 
I would have expected the 2nd gear reading to be 1.31-1.34KΩ, keeping the values increasing monotonically with gear number. A typo?
 
Yep, that is correct. The actual sequence they're listed in there is not correct either, from memory 2nd and 3rd were actually the other way around....I'll check the voltages this arvo and report back...
 
Time for me to but in, Here is a single digit https://www.sparkfun.com/products/9933 LED display and it could display N, and 1-6. LCD might be better for a motorcycle. You would have to multiplex the display and probably vary the intensity based on ambient light.

These **broken link removed** guys say they make a single digit LCD module, but you probably can't get a few.

A simple LED display could do, 0-6 where 0 is neutral.

Take a look at www.picaxe.com
 
Once you know the voltages you could convert them to a numeric display (a microprocessor with a built-in A/D and programmed to drive a display would be an easy way to do that).
Alternately you should be able to use an LM3914 dot-bar IC to generate the indicator signals if you just want a single-light indicator for each gear.

The quickshifter could likely be done with a voltage comparator on the strain gauge output driving a MOSFET switch. (Measure the voltage on the control module terminals to determine the required polarity for the switch.)
 
Hi gents, sorry for the lack of response, got tied up with other things over the silly season. I'll get back on to this next weekend :)
 
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