An R+D Thread - Different instruments.

MickeJagekrans said:

Ah, I see.

The big problem for me at the moment is that the speedometer only shows a zero no matter the speed so I'm guessing that the pulse either is not at +5V or that I am missing something else.
No rev counters lying around unfortunately.

I'm thinking that I should be able to measure voltage between the speed signal wire and ground to see what the pulse looks like and then try to convert it using an Arduino in case it doesn't look like it should (e.g. +5V baseline and 0V pulse).

Click to expand...

@DEcosse may know what voltage the speedo pulse from the ECU is.

I have a few Koso (and other) devices lying about - these I have driven from non-koso software driven sensors with no issues at all - I will have a look at their spec sheets. and get back to you. - There MAY be a ground reference issue as well.

Sorry, I don't know what the pulse rate is to the instrument;
the 5V thing triggered a thought though - I also don't know whether the ECU Output is 12V or 5V pulse (or whether there is a pull-up in the OEM instrument itself which may be required to generate the actual Source for the pulse out of the ECU - that could be the issue)

OK - some info.

Koso most certainly require a positive pulse - I am using a +5V-ish square wave pulse from the hummingbird GPS sensors with no problems. These also have a solution to give a 9.1V output - but it is not needed for Koso. Same with Koso revcounters and the generic Chinese thing.

The Smiths I have used in the past, also work from any old reed trigger sensor. Positive signal from sensor to instrument. Some are passive requiring a magnet to trigger switching - some active that detect changes in magnetic field. I have always used active sensors.

Acewell offer hall and reed triggering options. Their own 2 wire sensors are HALL.

BUT the latest MotoGadget instruments use a Negative pulse to trigger (I have one that came with the M-unit I put onto the old Guzzi).

And I think this is what his most esteemed @DEcosse is onto. It may well be that the speedo itself proffers a positive voltage via the "speed" wire which the ECU the switches to earth. Well that's my non electrictronics version. Pull-up and Pull-down get twisted around in my brain.

I'm pretty sure that the speed signal from the ECU is less than 12V since other threads elsewhere seem to imply that 12V would fry the Koso.
The ground reference shouldn't be an issue since pin 10 and 12 on the harness (ground) are joined somewhere on the main harness (can be seen on the wiring diagrams).

I'll wire up the RX2N with an external active speed sensor and later try to measure the pulse from the ECU.

Has anyone validated that the OEM ECU speed output works, even with the RX2N?









First - I have no idea what the output of the Keihin ECU really looks like
I DO know that the Sagem ECU in my Daytona uses a similar scheme for all it's outputs (whether driving relays or other functions INCL the speed output pulse)

The transistor itself is of course in the ECU - the resistor and supply voltage to the drain are both in the OEM instrument - this is called an "open-drain output" (or with BJT transistor it would be open collector - same thing in practice) - so if you connect an open drain output into a circuit that does NOT have a pull-up resistor in it , then it just won't output anything.

The voltage amplitude for the Koso - whether is 5V or 12V - measure the source voltage on the white wire out on the Koso speed sender harness and that will tell you whether it is operating at 12V or 5V - my guess is it is 12V but of course it might be 5.

What you can try (and this would be on your own head - if you blow up your ECU the risk is all yours )- connect a 5 or 12V via a 4k7 resistor to the speed output wire from the ECU and see if that does it (There should be fairly low risk if connecting via a resistor)
(the OEM Pink Wire Circuit to the ECU input Devices - like TPS, MAP sensors etc) is a 5V supply)

Sorry to revive this thread, but can the bike run without the stock speedo plugged in if you removed it for, say, a gps speedo/odo and spliced into the harness?