Large Spine Frame XS650 / Egli / Rau / Cafe Racer

Kicking around with some wiring components this weekend. Here is a snap shot of the wiring schematic...
The three major electronic systems are the Cognitomoto GPS Speedo, Power Dynamo digital ignition and Motogadget M-Unit...

I'm waiting for feedback from a couple of places on how to deal with the TACHOMETER pickup.
I'm hoping a couple of windings around a sparkplug cable will suffice. The Power Dynamo ignition system apparently doesn't support tach pick up that needs a
negative (-) side of the Coil. The GPS speedo/tach is looking for this.

Anyone have experience with this speedo set up/installation?

Here is a pic of the schematic. Anyone have questions or comments, fire away!
Schematic as of 031818.jpg

Also - anyone have experience shortening a GPS antenna cable?
Very apprehensive about cutting this cable. I could mount the Antenna within an inch of the speedo, or at the other end by the seat... The cable is 15 feet long!
 
Looks like you're missing a coil primary line.
The signal on the neg side of an ignition coil *can* be conditioned to drive things, like a tach. Maybe some ideas in here:

http://www.xs650.com/threads/an-led-ignition-timing-light-experiment.44586/

I've made GPS antennae cables, for Garmin products. Using BNC connectors and small diameter RG-178 coax. Google "RG178 coax connector" for ideas...
 
"2M", thanks. I see some more homework on my horizon. Think I might own a new crimping tool shortly (for the RG178)...

That timing light is pretty cool!

The Power Dynamo ignition system unfortunately doesn't use negative feed to the coil. I'm just kind of stumped at the moment on what I can use for the tach feed. The green wire, highlighted in yellow - is positive. Then the system goes to ground.
Power Dynamo green - positive coil.JPG
 
Okay, then you should show a ground symbol attached to the coil.

With your "inverted" ignition system, I would expect your green wire to show an inverted version of DogBunny's TCI trace (post #49 in that timing light thread). There should still be a >100v spike, just going neg first. If your tach only wants to see it go pos first, a simple line conditioner with resistors and diodes could do that. This really needs time in a lab, with a scope. Otherwise, just stabs in the dark...
 
This was aircraft related, so take it with a grain of salt.... I had to run a tach signal to a Dynon glass cockpit display from a Lightspeed electronic ign. box that didn't have a tach output. I tied into the pos. lead to the coil with a 50K resistor and ran that to the Dynon tach input. In the case of the Dynon, all it wanted was a pulse it could count... it didn't care about the polarity. I suspect your electronic tach just needs the same.... a signal that it can count the pulses from.
EDIT: I meant a 5K resistor. Damn fumble fingers.......
 
Last edited:
Updated with Ground symbol attached to the coil.
Schematic 031918a.jpg
So - maybe a 5K resistor in series - between the green coil wire and the yellow Tach cable?
Time on a scope... Other alternatives?

Here is a pic of the GPS antenna cable connector... The Cable is marked with: RG-174/U 26 AWG.
Any idea what this connector is?
GPS Antenna cable connector.JPG
 
Last edited:
So - maybe a 50K resistor in series - between the green coil wire and the yellow Tach cable?
Time on a scope... Other alternatives?
Have you tried to contact the folks that make the tach and see what they say? That's how I did it with the Dynon integration... I asked em. The Dynon Skyview cost about 5 grand (per side). I wasn't gonna let the smoke out without their input...;)
 
Yes, I have sent off emails to the tach manufacturer and the ignition manufacturers yesterday. I'll sit tight for a few more days before pinging them again.

Did get this from the seller of the Tach:
tach on positive terminal.png


Maybe I'm being Dense, but the "Advance Unit" of the Power Dynamo, doesn't quite match my image of an ECU. This diagram looks like a direct wire output from the ECU... I might be wrong but don't see this as the same green wire going to the coils... Am I wrong?
 
Am I wrong?
No. I think what they're trying to show is a hookup to an existing tach and they put the resistor on the wrong line. Should have been on the yellow wire. At least that's the way I see it.
But that does seem to intimate that all they're looking for is a signal from an ECU. Your electronic ignition qualifies as an ECU... it just handles the ignition instead of the whole engine.
I'd wait for them to respond, but I suspect that's what you'll wind up with, a stepped down tap (resistor) off of the coil signal.
 
The drawing in post#88 shows a "pull-up" resistor, 4.7k-10k. The ECU in that drawing will pull that tach line low during an ignition event, the yellow wire in that pic will see voltages of +14v down to 0.6v.

Your ignition's green wire (driving the coil) will see voltages of 0v up to more than -100v. A signal conditioner off that green wire could drive your tach...
 
Thank you Yes, that's it, it is an MCX type!
I had to google "signal conditioner" and it seems there are such devices available. Suggestions, recommendations? Something cheap, small, not too complicated?
 
I wouldn't be at all surprised to find the tach manufacturer built a signal conditioner into it... No answer from them yet?
 
Yes, they are helpful. As a back up plan, it looks like I can wrap the yellow wire around the spark plug wire (Min 3 times).
They also mention "conditioning the signal" may still be needed and keep check / take notice if the needle wanders above 3K RPM, TBD...

So, I guess I now have a plan for moving forward on tachometer and antenna details. If I can do something other than wrapping the wire, that would be cleaner... Like to hear more about these signal conditioners...

Thanks guys for all of your inputs!
 
OK.... just found and read the PDF instructions for your Cognitomoto GPS Speedo. First, there's this caution...
Important note: connecting the tachometer to the wrong wire will NOT damage the tachometer or your ignition. It just won't work!
So that tells me that it probably has signal conditioning built in.... or at the least, overcurrent protection.
Figure 1 shows the yellow wire tied to the coil ground wire...

Untitled.png


Does your coil have a ground wire or is it case grounded? 1 wire or 2? If it has a ground wire, problem solved... just tie the yellow into it. If not (case grounded), you'll need to make an isolated mount and run a ground wire from that... with the yellow tied to it of course.
 
Last edited:
Yes, it has one (+) wire, and case grounded. Isolating the coil, then ground it through the yellow wire / Tachometer? Sounds easy. Risks?
 
Yes, it has one (+) wire, and case grounded. Isolating the coil, then ground it through the yellow wire / Tachometer? Sounds easy. Risks?
No risk I'm aware of. As the warning sez... you won't break it. You don't want to ground through the yellow wire though... think in parallel...

MVIMG_20180320_233824.jpg
 
No guarantees... but if as I suspect, it's just looking for a pulse to count... it should be able to see one off that ground when the primary opens and the secondary collapses. Let us know.
 
Back
Top