I bought a new engine for my new to me Legend car. Legend buys the engines direct from Yamaha and the latest and greatest is an mt09 3 cylinder water cooled. Previous generations had a gear indicator but apparently the only option at this point for a gear indicator is a US Legends sourced custom dash mounted digital data panel that will show the gear as well as some other things. But it costs around $2,500 Canadian so I have no interest in buying it. Anyway, early reports say it won't reliably show what gear you're in. On the street bike, there is a gear indicator and a sensor on the transmission that plugs into the ECM. The ECM on the car is custom and not supplied by Yamaha and has no provision for plugging in this sensor.
the rectangle in the middle is a slotted shaft that mates to a slotted shaft in the transmission which rotates to a different point for each gear. The shaft in the sensor will rotate 360° but presumably when attached to the motor it will go back and forth as the shifts go up and down. Since it has three pins, I presumed it must be a potentiometer but I have tried applying positive and negative to two of the pins and tried to get a voltage signal from the third and failed. I have tried every combination even though from what I understand potentiometers typically have positive and negative on the outside two pins and the center is the one that supplies a variable voltage signal. But regardless of how I connected I get no signal from the third pin at all. So I'm wondering if someone can help me figure out how this sensor works, and how I might use whatever the signal is that it is providing to give a digital readout. There are simple and cheap gear indicators on eBay that take a signal from an ECM on a bike but I'm not sure they can use whatever signal this thing puts out to give me a display.
here is the car in progress for your amusement.
Just thinking out loud,
- Instead of measuring voltage between the third pin and ground, have you tried measuring from positive to the third pin (voltage or current)?
- Can you measure a change in resistance through any combination of pins as the sensor shaft rotates?
- maybe try applying positive to one pin and measuring current from each of the other pins to ground. (It may be a voltage divider)
Sure looks like a TPS.
Not sure how that the resistance in that one is wired, but I know some GM TPS for Electronic Throttle bodies have 2 different resistance profiles, the ECM tracks both for fail-safe operation.
Thanks for the suggestions. I've ordered what I'm hoping is the male end to that sensor which will make it a lot easier to play around with it. Am I correcting assuming it's got to be some kind of a voltage signal? I have only looked for voltage to this point.
It's possible to be a hall effect sensor, but that'd be a bit loony.
In reply to Pete. (l33t FS) :
Wouldn't a Hall effect require rotation? Sounds like this is positional.
If you have ground speed and engine rpm, you can infer gear selection.
Keith Tanner said:
In reply to Pete. (l33t FS) :
Wouldn't a Hall effect require rotation? Sounds like this is positional.
If you have ground speed and engine rpm, you can infer gear selection.
That is how the bike does it. But the Legend has no speedo
bearmtnmartin (Forum Supporter) said:
Keith Tanner said:
In reply to Pete. (l33t FS) :
Wouldn't a Hall effect require rotation? Sounds like this is positional.
If you have ground speed and engine rpm, you can infer gear selection.
That is how the bike does it. But the Legend has no speedo
Don't need a speedometer, just need to know the speeds of trans input shaft and trans output shaft. Ratio between the two is whatever gear you are in.
Silly question and I might have misunderstood your post but do you care if have a gear display?
I don't have a coherent strategy based on what you find, but have you checked resistance between 1-2, 2-3, 1-3?
Any chance you let the smoke out while testing the potentiometer theory? How much voltage did you use? (Wondering whether being a plugged-into-logic-electronics thing it was expecting 5V and was unhappy with, say, 12V... though honestly that feels more like stirring the factoid soup in my head than a likely outcome at that kind of voltage, unless it was 12V across two pins that really didn't like that)
While trying to sanity check that train of thought I learned about Digital Potentiometers. I wonder whether that's a possibility on a new bike. I need to go do a thing or I'd start down that rabbit hole, too...
Tom1200 said:
Silly question and I might have misunderstood your post but do you care if have a gear display?
I have raced bikes and being in the wrong gear is no big deal. It bogs or the back wheel locks up. But one of my friends tore his diff apart after dropping three gears instead of two last year so he is buying the problematic $2500 panel. It is sequential so probably easy to lose count. I would rather know where I am at, but for less money.
Keith Tanner said:
In reply to Pete. (l33t FS) :
Wouldn't a Hall effect require rotation? Sounds like this is positional.
Nope, Hall effect can be positional, most game controllers use hall-effect sensors for the analog sticks these days. I've even seen a DIY'ed 3d hall-effect "space mouse."
In reply to Keith Tanner :
Here's a Texas Instruments article that talks a little about linear Hall Effect sensors -> https://www.ti.com/document-viewer/lit/html/SSZT164
They could also be using an encoder or RVDT to measure rotation, but either one would add more cost and complexity.
I'm pretty sure I have not let the smoke out. I'm using a dead battery that's giving 10 volts and I have not shorted anything. But having said that I'm going to wait until I get the correct connector so I can have three pigtails to play with. I have not tried resistance yet but I'm not sure how resistance could be used to provide a signal to an ecm. I thought that an ECM generally used voltage and typically 5 volts to generate data.
Is this a switch and not a resistor? Shifter rotates one direction on up shift the other direction on down shift. Each shift creates a pulse up or pulse down. Just count the ups and downs to know which gear you are in.
Healtech makes gear position indicators for a lot of modern bikes. I'm not sure what engine you have but you can search their site by bike to see if they have one for yours. Most of their systems look at rpm and the speed sensor from the output shaft to figure out what gear you're in. They have an LED display that shows the gear.
In reply to bearmtnmartin (Forum Supporter) :
Resistance is how the X volts in gets turned into Y volts out. It's another way of looking at a potentiometer without running significant current through it.
I got mixed answers on whether 12V (and I know you were using 10V) would cook a 5V rated pot. I think one of the clues about how this could happen is the rheostat vs voltage divider usage cases laid out here: https://randomnerdtutorials.com/electronics-basics-how-a-potentiometer-works/ where I believe the "voltage divider" case is how it's used in the installed case you're referring to, but you can inspect it as a rheostat with an ohmmeter with, I think, a reduction in the probability of cooking anything.
Basically, if you put 10V across the outer pins of a 5V pot, you might well cook it as you'd be driving twice as much current through it as it's designed for, I think (Ohm's Law). There may be an expectation about how little current a 5V logic circuit can supply as well, but I'm not sure about that.
DrMikeCSI said:
Is this a switch and not a resistor? Shifter rotates one direction on up shift the other direction on down shift. Each shift creates a pulse up or pulse down. Just count the ups and downs to know which gear you are in.
That's possible if the sensor connects to the shifter pedal's shaft, the dash would just have to assume that the bike always powers up in 1st or neutral, which should be what happens if nothing is broken. If it's attached to the sequential gear selection shaft then it can't be a switch though.
GameboyRMH said:
In reply to Keith Tanner :
https://hackaday.com/2024/08/25/a-simple-6dof-hall-effect-space-mouse/
Well E36 M3. Do I need to build one of these just so I can get a 6DOF controller working with games?
Kubotai said:
Healtech makes gear position indicators for a lot of modern bikes. I'm not sure what engine you have but you can search their site by bike to see if they have one for yours. Most of their systems look at rpm and the speed sensor from the output shaft to figure out what gear you're in. They have an LED display that shows the gear.
I have been told the Healtech site as someone here referred me there looking for a tach. But their stuff is all based on the factory ECM.
I will update this thread when I get the plug end so I can play with the sensor more easily.
