Where to tap speed sensor signal?

[the Ferret]

Huh?

I’m going to need to post my greek picture again.

Read post #44 above for what I am trying to do.

Seems a lot of other brand and models of bikes are using the analog input for the gear setting.

Everything I have read said I should be looking for a 0-5v.

So as you guys mentioned above I tapped the green/pink with the red lead, black to a chassis frame screw for ground, dcv setting since I am on a vehicle and not in my house 120v ac.

Yea- I have no idea. What am I missing? Please reference post 44 above. I’m going to bed. Will check back tomorrow. Thanks!!


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OOOOOHhhh now I get it. very funny Dubs

[Lord Popgun]

Powerdubs, what you are missing is that the sensor is not connected to chassis ground. Its 2 wires go directly to the meter. If you are going to read anything you will have to put the probes on both of the sensor wires.

[SportsterDoc]

Powerdubs, what you are missing is that the sensor is not connected to chassis ground. Its 2 wires go directly to the meter. If you are going to read anything you will have to put the probes on both of the sensor wires.

Ditto
CB1100 meter has VSP + (p/w) and VSP - (g/w)

[egleaves_imp]

Powerdubs, what you are missing is that the sensor is not connected to chassis ground. Its 2 wires go directly to the meter. If you are going to read anything you will have to put the probes on both of the sensor wires.

So the meter receives two signals and interprets the differential as your speed, right? Then I would expect that the wire going from the meter to the ECM would be the one carrying the signal I need to send to my brake module. Probably the same for a power commander.

[SportsterDoc]

Powerdubs, what you are missing is that the sensor is not connected to chassis ground. Its 2 wires go directly to the meter. If you are going to read anything you will have to put the probes on both of the sensor wires.

So the meter receives two signals and interprets the differential as your speed, right? Then I would expect that the wire going from the meter to the ECM would be the one carrying the signal I need to send to my brake module. Probably the same for a power commander.

One signal.

But it takes both wires to complete a circuit to measure the signal.

I can touch 120 VAC and not feel it, if I am not grounded.

Tapped into the white on the rear speed sensor (changes to green/pink under side cover.)

Put my meter on it, dcv setting, other lead grounded to a screw. Started bike on center stand and put it in first. No reading.

Thoughts?


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Which screw?
What is resistance from that screw to battery negative post?

[PowerDubs_imp]

Sorry guys. Any time I have tested for voltage in a car, in a house, in a appliance or a device all I have ever needed to do is one lead to whatever source I am testing and one lead to chassis.

In this case since the power commander is only wanting one wire input, I am unsure how that is any different than my meter lead.

Also confusing is that the power commander has a speed input spot, but in many of the directions online they say some bikes can use the 0-5v input instead if needed. I think there is a spot in the software to tell it which input you are using when you set it up. They don't give much technical details on what exactly the speed input requires or how it functions.

[Lord Popgun]

Egleaves, you need to understand that the line from the Meters to the ECU is a bi-directional serial data line. Data goes back and forth. Its not just a stream of speed data to the ECU. Don’t mess with the serial line.

Dubs, it is not unusual in electronic circuits to have circuits or parts of circuits not connected to chassis ground. My guess is the speed sensor, a Hall effect device, outputs on +and - to a receiver, like maybe an op amp, and outputs a single pulse to the rest of the circuitry in the Meter assm. It gets a little involved for a discussion here, but no chassis ground is needed in a circuit like this. Although the receiver chip most likely has power and a chassis ground. Confused yet

If it cools off some and I feel like it, maybe I’ll put a scope on the line and see whats up. Maybe.

[max]

Hi Josh, i had a look at the multi function pdf and it mentions a transmission speed sensor, which is 1 wire ;
Multi-Function Hub -

Most modern fuel injected bikes use a transmission speed
sensor. The Hub can be tapped into this sensor to display
vehicle speed and also to be used as a gear position
display for bikes that do not have a rotary type sensor
1 Locate the signal wire of the speed sensor (refer to the
service manual, NOTE section of this guide, or
http://www.powercommander.com).
2 Crimp the supplied wire tap to this wire.
3 Connect the BROWN wire from the HUB harness to the
wire tap.
pdf link here; https://www.mpsracing.com/instructions/D...nstall.pdf

Our sensor is a different one like this;



The problem as popgun described very well is that it is what is known as a differential sensor, meaning it electrically floats with respect to chassis ground and the sensor circuit is designed to look at the DIFFERENCE between the two wires, the reason for this is the position of the sensor, you can mount it anywhere on the bike without having to worry about grounding the front fork hub or similar part to ensure a good return signal ( ground ) even after years of use.
However if you wanted to use the signal for another purpose you would have to look at both wires and specifically the difference in signal between the two
( See peter baron's scope pictures and notice the voltage of the pulses goes over and under 0.6 volts )

If you were lucky and had an abs model cb1100 there is a possibility to use the pink/green wire that runs between the abs unit and the instrument cluster, which carries a higher level ( 0 to 5 volt with respect to ground hence ONE wire, i think ) pulse signal that uses a separate input on the cluster specifically for the abs signal which the power commander unit " understands".

What essentially happens; inside a digital ( 0 to 5 volts ) input is a transistor.
transistors start conducting ( switching on ) above 0.6 volts, so the input senses a 0 volt input and sees this as a "low" signal,
as soon as the transistor sees more than 0,6 volt it switches "on"and tells the processor it has a "high" signal,
the tempo that it sees low to high pulses determines how much the processor drives the speedometer.
This video shows the pcv connected to the gear speed sensor at the ecm ;
https://www.youtube.com/watch?v=QfHOrQaow34

So our speed sensor uses an entirely different input circuit and can possibly be damaged by applying external voltages to either of the two input wires, what is pherhaps not realized is that in the course of things we learned over the years i made many mistakes that broke a lot of equipment in the process, we don't want to cause this to anybody else and warn them if we can see a potential problem on the horizon which may not be obvious to them.

I suspect you knew some of this already but i thought i would tell the whole story for everyone's benefit and in addition to popgun's advice.

[egleaves_imp]

Egleaves, you need to understand that the line from the Meters to the ECU is a bi-directional serial data line. Data goes back and forth. Its not just a stream of speed data to the ECU. Don’t mess with the serial line.

Dubs, it is not unusual in electronic circuits to have circuits or parts of circuits not connected to chassis ground. My guess is the speed sensor, a Hall effect device, outputs on +and - to a receiver, like maybe an op amp, and outputs a single pulse to the rest of the circuitry in the Meter assm. It gets a little involved for a discussion here, but no chassis ground is needed in a circuit like this. Although the receiver chip most likely has power and a chassis ground. Confused yet

If it cools off some and I feel like it, maybe I’ll put a scope on the line and see whats up. Maybe.

Understood.

All that's left is the VSP+ and VSP- wires. If they're just two sides of a continuous circuit then we should be able to "listen in" by tapping onto either of those wires since they carry the same signal.

Am I way off again?

[Lord Popgun]

I think the answer is maybe. Might have to tap both lines and input them to a differential receiver that then outputs one pulse. Max, what say you?