Questions about gauges and sending units

[DiverRay]

T.C.,
Go with an 18 or 20 gauge wire, fine strand if you can find it. This will act as LESS of an antenna. The other trick is to use a ground BRAID for a good ground between the box and the frame ground. Think the main ground between the frame and the middle drive.
As a final solution, you can put a ferrite bead on each end of the wire. This looks like a clay donut, or clamshell affair. run the wire through about three times on each one to help get rid of any RFI.
All tricks we use on test benches at work, trying to fix radio's.

[3Phase]

Test The Tach On Another Vehicle

Good call on the wire size and filters, Ray!

T.C., you want to use the smallest gauge wire you can find that won't blow away in the breeze like a gossamer spider web but before getting carried away -- test the new tach on another vehicle.

Put the tach input on the coil negative lead of your car or truck and see if it works correctly. If the tach works, it's time to figure out what's making it go all Goofy on Godzilla!

Using a tap on the pick-up coil wire for the tach input on your XS11 is interesting because it worked but it's a bad idea because it puts a parasitic load on the pick-up coil. That can make the ignition misfire if the signal gets lost or garbled somewhere between the pick-up coil the the TCI.


<WoolGathering>
The amount of built-in noise filtering and shielding in the tach is the difference between an inexpensive tach and one of the brand name units. You get what you pay for. The tach itself should be pretty well shielded by that honkin' aluminum housing but as Ray says, the wires act like antennas. From the way the RPM reading changes on the tach I'd suspect the alternator.

Alternator ripple voltage is transmitted throughout the entire electrical system but it's usually pretty well damped by the vehicle battery and electrical load. The load on the alternator from the motorcycle battery and electrical load may not be large enough and if the tach will work with the voltage/current from a thirty-year-old ignition pick-up coil then the alternator ripple can fire the tach until the ripple frequency goes outside of the range the tach can read.
</Wool>

.

[TopCatGr58]

Hey again Ray/Scott,

Thanks for the tips/tricks. I double checked the wire, it is 18 Ga fine stranded...16 strands...counted them!

Secondly, the BOX is bolted directly to the TT with SS bolts/nuts, the box is aluminum, the mounting bracket is aluminum, so it should be well grounded to the frame. The Gauge cluster had it's own GROUND wire that was connected to one of the ground wires in the headlight harness.

Because of the difficulty and TROUBLE in both wiring it up and mounting it to the bike....I won't be taking it off anytime soon for troubleshooting. I perhaps could run another longer TACH feed wire so that I could connect it to my car's coil. The bike gauge will work with just the key on without the engine running so I won't get interference from that.

I like the idea of the Ferrite beads on both ends, much easier to install.

Scott, I only did a TEST connection to the TAP on the pickup coil trigger wire. The gauge is connected to the NEGATIVE side of the Ignition/spark plug coil that then goes to the TCI(Orange or Gray) wire, can't remember which...but the actual Pickup coil wires are NOT spliced into, just the ignition coil trigger wires.

The Mini-Alt's output is about twice as much as the OEM ALT, so it's not straining as much to drive the bikes electrics...especially with almost ALL LEDs, and the HID headlight, and new AGM battery. SO...that could be a contributing factor for sure.

It looks worse in that video than it is. After I installed/mounted my new Shinko front tire, I took it out for a spin to top up the gas and just get the wind in my hair for a few moments. The tach works flawlessly while riding down the road. ONLY when I would come to a complete stop, and the rpms' dropped to ~1500 would it then occasionally bounce, but once getting under way it was rock solid, I never run below 2500 rpms anyways! SO....if the Ferrite donuts don't work, I can live with it this way.

Will keep you posted on any success, and then add that to the pending TECH TIP for this possible mod!

T.C.

[3Phase]

Run A Tachometer From A Cigarette Lighter

Thanks, T.C.!

You know, I don't believe I'd pull the tach to try it on a car either! Yes, use a longer wire but not so long that it can pick up interstellar signals from Voyager 1.

Connect a ground wire from the bike to the car (like, one half of a pair of jumper cables) or the tach on Godzilla may do, uh, unpredicatable things without the ground return path to the car's electrical system.

FWIW I think the tach is fine, it's just picking up the alternator pulses along with the ignition pulses but it can't trigger fast enough to use them once the engine RPM goes up so the ignition signal takes over.

There's at least one company that makes a tachometer that works from a cigarette lighter:-
RPM-8000-PRO

Sensorless automotive RPM measurement with LCD display and easy calibration


I remember somewhere you did the math for the number of pulses on one of the stator White wires on your XS11 and it was the same for the new Mini-Alt . Multiply that by three and there's the ripple frequency, then add the pulses from the ignition, both the one connected to the tach input and probably the one pulsing its little high voltage inductive heart out right next to it and see if that roughly matches up with what the tachometer is showing you at low RPM.

.

[BA80]

Installed a Flux Capacitor on Ol' Okie today. It drank all my beer and ate the cans too.


BTW.......what year is this?

[BA80]

See, it transported me to the wrong thread.

[bikerphil]

TC, I have solved many electrical interference problems just by simply adding a capacitor in parallel to the device. For example, a digital volt meter I added to my XS would work erratically with the engine running but fine with it off, adding the cap eliminated the problem. JAT

[TopCatGr58]

Hey Phil,

I don't mean to be dense, but I only have 1 wire going from the ignition coil to the Gauge cluster/tach. The gauge does have a positive and negative set of wires for actually powering the device. Are you suggesting putting the capacitor on the gauge's 12V + and - wires?

From what we've discussed earlier here, it's felt that the RF interference is coming from the single ignition coil tap wire, not from the unit's main power connections.

I worked late today, so wasn't able to run by Radio Shack for the Ferrite donut(s) to install/try!

T.C.

[bikerphil]

You could try it either way TC, the red and black main power, or the red power and the neg tach wire. A 47 or 470uf cap can be found/salvaged from just about any junk electronic device you have laying around. I have never had any luck with those ferrite sleeves ever helping any, YMMV. Good luck!

[3Phase]

T.C.,

Yes. What Phil said. Put capacitors between the Input wire, the 12 volt supply wire, and Ground. Ferrite beads will help with the even higher frequency RF generated by the spark plugs and there are even more down-and-dirty options available BUT test the tach first to make sure it's working.



IF it's noise making that tach go nutz it MAY be coming in on the tach Input wire AND/OR the 12v supply wire AND/OR the Ground AND/OR all three -- it's noise and we're all pulling stuff out of ... guessing wildly until you test the tach on another vehicle.



Is there a second or selectable input voltage selector/option, even another input jack somewhere on the tach for using a 12 volt signal instead of a (??) millivolt signal? Right now you've basically got a live microphone with the gain maxed out and the volume cranked up to eleven! There are at least three waveforms superimposed on one another:

1) The actual 12 volt signal you want from coil negative wire to the tach Input
2) The induced signals from the second coil and spark plugs
3) The millivolt ripple from the alternator


With the tach 12 volt supply wire AND the tach Input wire both running along the frame and under the fuel tank it's like walking through a room with three different sprinklers turned on, wondering where all the water's coming from and which sprinkler got you wet!

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