# Noisy RPM Signal



## lowcrawler (Jun 27, 2011)

gottdi said:


> Well it's actually a WarP Speed Sensor from RechargeCar and not affiliated with Netgain. It is just designed for the Warp motors.
> 
> Try backing the sensor away from the ring. Keep trying until you get a clean signal. If it gets too close it mucks things up a bit. Many think you need to put it real close, you don't. Don't want it too far away either. Find a happy medium.


Interesting. That's exactly what I did -- put it really close. I'll back the sensor off a bit and see what happens.


Any thoughts on 2 points vs 4?


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## Joey (Oct 12, 2007)

The Soliton manual recommends an inductive sensor for better noise immunity. I suspect the commutator end of the motor is fairly noisy.


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## DIYguy (Sep 18, 2008)

lowcrawler said:


> I've got a Netgain Speed Sensor attached to my Warp 9... Given it came with 4 of the 'target' set screws, I used all 4... Setting my Soliton Jr to look for 8ppt input.
> 
> I was thinking that if I went to 2 set screws (4ppt) that might help the signal rise above the noise? Not sure... thoughts?


How do 4 set screws get you 8 ppt? and 2 set screws get you 4 ppt? 
Am I missing something??


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## Tesseract (Sep 27, 2008)

lowcrawler said:


> ...
> I've got a Netgain Speed Sensor attached to my Warp 9... Given it came with 4 of the 'target' set screws, I used all 4... Setting my Soliton Jr to look for 8ppt input.


Firstly, "ppt" means "pulses per turn"; if your target has 4 setscrews then you set ppt to 4, not 8.

Secondly, it seems that everyone who uses this sensor with our controller complains about "noise" or "erratic RPM". We test every controller on our dyno prior to shipment but we use a cheap $20 inductive proximity sensor with 25' of cable draped all over Hell's half acre to read RPM. Despite this less-than-optimal setup with a seemingly cheap sensor, we don't have any problems reading RPM on our dyno setup. Things you can try before giving up and buying an inductive prox are:

1. Back the sensor away from the target. How far? Depends, but you can try 1/4" to start.
2. Add another pullup resistor of 2.2k to 4.7k in parallel with the built-in one (NB - this resistor goes from TACH to S12V).
3. Use just two of the 4 setscrews (directly opposite ones, not adjacent!)
*4. Ensure the cable from the sensor does not run parallel and/or next to either the battery or motor cables.*

If you still have problems with the tach acting erratically then buy the same prox we use from Automation Direct.


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## lowcrawler (Jun 27, 2011)

Tesseract said:


> Firstly, "ppt" means "pulses per turn"; if your target has 4 setscrews then you set ppt to 4, not 8.


The directions seem to indicate that it puts out two 'pulses' per set screw per turn. Maybe I'm wrong and I over-revved the krunk out of my motor? Check the top half of page 3: http://evolveelectrics.com/PDF/NetGain/Speed Sensor Kit.pdf

_ Set your gauges to monitor the number of cylinders equal to twice the number of pulses per revolution. For example, use 8 cylinders if you have 4 set screws (4 pulses) on your exciter ring_

Through testing myself, this seemed to be true... I did some calculations on what my 'redline' (set at 5250) speed would be in each gear and then set the Soliton Jr to 4ppt. Each time the it hit 'high RPM' and cut power on me at roughly half the speed I expect... in 1st, 2nd, 3rd, and 4th gear.

So I used the web interface to change it to 8ppt and the expected 'redline speed' and the actual 'redline speed' matched up.

I do agree that it was weird that 4 screws means 8ppt... but that's the way it worked out. I'll have to mess with stuff... clearly this isn't right right now.


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## piotrsko (Dec 9, 2007)

FWIW: the instructions seem to be meant to drive a standard issue automotive tach which likes data divided by 2. For an 8 cylinder engine/ tach you would need 4 screws which gives you 8 pulses every other turn (4 stroke engine). 

A Soliton ISN'T standard automotive issue, it is way better, so Tess uses direct reading. 3 bumps makes 3 pulses per rev like Tess said. My install was a 6 cyl, so I have 3 bumps with the Sol using 3 as the input and 3 as the output to the tach. 

Also some grounded braid on the outside of your cabling makes the signal much less prone to them stray RF electrons floating about the engine compartment. I suppose grounded alum foil wound around the cable would work, too, but that is considered rather inelegant.

Ideal gap is around 1/16 (up to 1/8) for this sensor with the center of the sensor centered on the center of the screw. too close and it tries to read the shaft, too far and it tends to skip pulses. Works well in my installation (see Frankenranger in my garage)


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## Tesseract (Sep 27, 2008)

lowcrawler said:


> The directions seem to indicate that it puts out two 'pulses' per set screw per turn. Maybe I'm wrong and I over-revved the krunk out of my motor? Check the top half of page 3: http://evolveelectrics.com/PDF/NetGain/Speed%20Sensor%20Kit.pdf


I don't see where you get the impression that the sensor puts out two pulses per setscrew. Indeed, look at the text you already quoted from the manual which I have put in bold:

_



Set your gauges to monitor the number of cylinders equal to twice the number of pulses per revolution. *For example, use 8 cylinders if you have 4 set screws (4 pulses) on your exciter ring*

Click to expand...

_At any rate, I just got a reply from another customer having problems with this sensor and it turned out that moving the sensor's cable away from the motor cables, which it was originally tied alongside, solved the problem.

Folks, I can't emphasize it enough - a Soliton controller is the electrical noise equivalent of 6 legal limit AM radio stations in a box. Do not underestimate the possibility of problems from the electrical noise radiated by the motor or battery cables in an EV!


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## lowcrawler (Jun 27, 2011)

Tesseract said:


> I don't see where you get the impression that the sensor puts out two pulses per setscrew.


I drove a known speed producing a known RPM by doing transmission and final drive calculations.

When I had it at 4ppt, the Soliton Jr was registering exactly 2x the number of RPM than it should have been. That's where I "get the impression".

At 8ppt, it was registering the 'correct' number of RPM's (though with a very noisey... thus this thread)

It could very well be that it's registering each set screw twice or something. I'm going to do some tests next time it's not raining... *grmble...grubmle*


fwiw - the cable doesn't run anywhere near any traction pack cables. The closest it ever gets is when it connects to the motor and connects to the Soliton... the rest of the path runs in a 'rainbow' around all the rest of the HV stuff.


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## Joey (Oct 12, 2007)

There are two places to configure the tachometer with the Soliton. You set the number of pulses per turn at the soliton tach input, and you set a soliton output to drive the tachometer. It is possible to have a error in both of these settings and get the correct tach reading on the dashboard, but have incorrect motor rev regulation in the Soliton. 

Most stock tachometers require a number of pulses per revolution equal to half the number of cylinders in the original engine.

You might need to get an o-scpoe on the tach sensor and see what the waveform looks like. It might be triggering twice on the set screw socket.


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## lowcrawler (Jun 27, 2011)

Update:

Backed the sensor away to about 3/8", removed 2 set screws, set soliton jr to 2ppt....

Perfect reading, smooth, correct number, etc...

Thanks all.


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