SuzukiSavage.com - Rotor pulses?

360k+ Serious Thumper Offline Savage heart of darkness Posts: 680 Cartersville, GA Gender:	Rotor pulses? 05/17/12 at 19:07:34 Has anyone ever probed the rotor pulses to see what their analog characteristics are? I'm curious because it would be easy to design an LED readout tach for a few dollars that could be mounted near the speedo. If not, I'll test the pulses and post results here (I have a scope).
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Serowbot YaBB Moderator ModSquad Offline OK.... so what's the speed of dark? Posts: 28644 Tucson Az Gender:	Re: Rotor pulses? Reply #1 - 05/17/12 at 19:16:43 I don't even know what a rotor pulse is... ...but, I'd sure like to see one, if you're willing to explain what I'm lookin' at... ... Neat!.. Sumpin' new!... That'll be great... ...
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Rotor pulses? Reply #2 - 05/17/12 at 19:40:41 Scope it out & let us know,, then splain how the tach works,, I survived electronics in the Air Force,,dang near 40 years ago, so Im sharp as a bowlin ball,, but I still understand some of it,
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Dj12midnit Serious Thumper Alliance Member Offline If you'r here and I'm here isn't this our time? Posts: 1036 Lynden Wa. Gender:	Re: Rotor pulses? Reply #3 - 05/17/12 at 19:41:35 I thought rotor pulsing was caused by getting a hot rotor wet?
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thumperclone Serious Thumper Alliance Member Offline PGR rider riding with respect Posts: 6056 Grand Junction Colorado Gender:	Re: Rotor pulses? Reply #4 - 05/17/12 at 21:38:56 why not pick up a signal from the ignition coil like most tachs do.. my lcd tach pick up is induced from the plug wire..
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360k+

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Re: Rotor pulses?
Reply #5 - 05/18/12 at 08:46:10

thumperclone wrote on 05/17/12 at 21:38:56:

why not pick up a signal from the ignition coil like most tachs do..
my lcd tach pick up is induced from the plug wire..

The rotor is the counterpart of the stator in the alternator, and constitutes the spinning component. Rotor pulses are generated by a special magnet on the rotor passing by a stationery coil (sensor). This pulse ultimately determines ignition timing, and there is one rotor pulse per engine revolution.

There are a few of places on the engine where rev pulses can be detected with advantages and disadvantages to each. One problem with ignition coils is they have a nasty side effect of producing high voltage spikes which could be detrimental to a microprocessor. However, the spikes can be mitigated by taking some precautions such as the use of zener diodes. While I'm looking at the rotor pulses I will also scope the coil's primary pulse to determine it's suitability.

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teabowl13 Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 535	Re: Rotor pulses? Reply #6 - 05/18/12 at 12:23:22 WHOA!! Gettin' Nerdy up in this Hizzie.... (sorry.... been a long week, I couldn't help myself. All in good fun. ENJOY!)
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prechermike

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Re: Rotor pulses?
Reply #7 - 05/18/12 at 12:28:33

360k+ wrote on 05/18/12 at 08:46:10:

thumperclone wrote on 05/17/12 at 21:38:56:

why not pick up a signal from the ignition coil like most tachs do..
my lcd tach pick up is induced from the plug wire..

The rotor is the counterpart of the stator in the alternator, and constitutes the spinning component. Rotor pulses are generated by a special magnet on the rotor passing by a stationery coil (sensor). This pulse ultimately determines ignition timing, and there is one rotor pulse per engine revolution.

There are a few of places on the engine where rev pulses can be detected with advantages and disadvantages to each. One problem with ignition coils is they have a nasty side effect of producing high voltage spikes which could be detrimental to a microprocessor. However, the spikes can be mitigated by taking some precautions such as the use of zener diodes. While I'm looking at the rotor pulses I will also scope the coil's primary pulse to determine it's suitability.

I was just getting ready to say that. Huh

Serowbot splained it to me. Cheesy

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MarkHB Junior Member Offline Go for it! Posts: 88 Ottawa, Canada Gender:	Re: Rotor pulses? Reply #8 - 05/18/12 at 17:20:51 My EE spider sense is tingling. I can't wait to see the scope plot!
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360k+ Serious Thumper Offline Savage heart of darkness Posts: 680 Cartersville, GA Gender:	Re: Rotor pulses? Reply #9 - 05/18/12 at 18:23:55 OK, I've got the scope data, but lemme ask... as a forum noob with 5 or 6 total posts is it going to allow me to post my jpgs? Admins or moderators?
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Re: Rotor pulses?
Reply #10 - 05/18/12 at 19:35:41

OK, I think I have pics figured out now. Warning, technical discussion follows...

The first 3 pics show the rotor pulses at 3 different engine revs. The last shows the coil signal, and why I am trying not to use it. The rotor pulses show the scope across the coil wires with no ground reference at all (i.e., floating). The coil pic shows the connection between the ignitor output transistor and the coil primary as referenced to ground. Don't worry too much about the rotor pulse voltages as that can be reshaped to anything I want, but do pay attention to the wave shape and period (timing).

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MarkHB Junior Member Offline Go for it! Posts: 88 Ottawa, Canada Gender:	Re: Rotor pulses? Reply #11 - 05/18/12 at 19:43:18 Wow, the coil really rings. What digital hardware are you planning on using?
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Re: Rotor pulses?
Reply #12 - 05/18/12 at 20:18:44

Ahhh, I am detecting another engineer pod here. Ignition coils actually tend to act like flybacks, thus producing a duration period for the spark. I thot I had another picture that showed more than one coil pulse at speed, but I guess my camera decided not to take the pic (remember the days when WE HUMANS decided? LOL)

Anyway, the rotor coil has a nice consistent wave form as I suspected. I was planning on rectifying the pulse, disregarding the negative side (magnet leaving coil proximity), then buffering and clipping to a square wave and feeding to an MPU.

I'm not sure about the output yet, and wanted to get some feedback here on the forum. One idea I had was to use a 2 digit LED display showing the 1000's and 100's of RPM, discarding the 10's and ones. If that much resolution is not needed, a bar graph LED array might even work, and would give you resolution to the nearest 1000 RPM. The display should probably be something that can be grasped in a glance without having to think. Hopefully, some other ideas will surface.

BTW, I am a retired engineer (Apple - 20 years).

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thumperclone Serious Thumper Alliance Member Offline PGR rider riding with respect Posts: 6056 Grand Junction Colorado Gender:	Re: Rotor pulses? Reply #13 - 05/18/12 at 23:23:04 bar graph led tachs are on the market, pricey boogers tho.. can you do what you are trying for under $35 retail.the plug wire fed lcd display tachs can be had for around $35. think northern tool has one.. mine says pit posse on it, had it on thumperclone(chinese ct70) b4 i bought my ls
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ratz

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Re: Rotor pulses?
Reply #14 - 05/19/12 at 07:54:35

360k+ wrote on 05/18/12 at 20:18:44:

Ahhh, I am detecting another engineer pod here. Ignition coils actually tend to act like flybacks, thus producing a duration period for the spark. I thot I had another picture that showed more than one coil pulse at speed, but I guess my camera decided not to take the pic (remember the days when WE HUMANS decided? LOL)

Anyway, the rotor coil has a nice consistent wave form as I suspected. I was planning on rectifying the pulse, disregarding the negative side (magnet leaving coil proximity), then buffering and clipping to a square wave and feeding to an MPU.

I'm not sure about the output yet, and wanted to get some feedback here on the forum. One idea I had was to use a 2 digit LED display showing the 1000's and 100's of RPM, discarding the 10's and ones. If that much resolution is not needed, a bar graph LED array might even work, and would give you resolution to the nearest 1000 RPM. The display should probably be something that can be grasped in a glance without having to think. Hopefully, some other ideas will surface.

BTW, I am a retired engineer (Apple - 20 years).

And here's a schematic! (Sorry,I couldn't resist!) I'll see if I still have my scope data from a previous excursion into the unknown.

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circuit_diagram.png

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