Topic: Strange Tach on my 2 smoker....Electrical Experts needed.

[kghost]

I'm Scratching my head........

I've installed a Acewell 4553 Gauge on my Kawasaki KR-1.

After following ALL the directions I still can not get the tach function to operate properly.

As you can see in this video......it works properly driven off the CDI tach output until 6000-7000 RPM at which point it falls dead.

http://youtu.be/ohZHJXsUBYk

The only way I can get it to operate is by including a 100,000 - 150,000 ohm resistor in series with the gauge and then JUMPING the resistor with finger contact on both sides....

See Video

 
http://youtu.be/58FQLrnk-08

Anyone smarter than me want to tell me what I am missing?

Thoughts?

[scottly]

Your fingers are adding capacitance to the circuit; try adding a small capacitor in parallel with the resistor. 

[kghost]

Your fingers are adding capacitance to the circuit; try adding a small capacitor in parallel with the resistor. 

Was thinking of that.......what size?

[Duke McDukiedook]

Something small, .01uF poly cap @ 100V sound right?

[kghost]

Near as I can tell.....

There's a bit of DC and AC on the line.

About 2 volts max that I can measure.

I'm going to get several capacitors and a diode and give them a try

[scottly]

Check out this thread....
http://forums.sohc4.net/index.php?topic=119760.msg1362018#msg1362018

[scottly]

Something small, .01uF poly cap @ 100V sound right?

The cap should be connected from the tach side of the resistor to ground. Use the smallest size that will allow proper operation.

[kghost]

Just an update. Solved

I wound up with a 200 pF Capacitor in PARALLEL with a 1 mohm resistor.

It wiped out the AC in the line and the resistor dampens sufficiently.

[Duke McDukiedook]

Wouldn't a diode have done the same thing?

[scottly]

The 200 pF cap is passing AC to the tach; the wiring I suggested would have shunted the AC to ground, effectively removing it. The tach needs some AC signal to operate. I wonder if the 1 meg resistor is required? It would be helpful to use an oscilloscope to see what is going on.. 

[kghost]

The 200 pF cap is passing AC to the tach; the wiring I suggested would have shunted the AC to ground, effectively removing it. The tach needs some AC signal to operate. I wonder if the 1 meg resistor is required? It would be helpful to use an oscilloscope to see what is going on.. 

I was sitting in the shop before I posted the question thinking exactly the same thing.

Sadly I didn't have one lol