work in progress stimulator board

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Sudo
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Re: stimulator board

Post by Sudo »

abecedarian wrote: Image.
That is NOT the wheel being used for the 24 teeth. I had the 97 accord myself. The teeth look more like what I showed you.

Again, for the sole purpose of my critizism. I am talking about the 24 teeth!! Not the 1 teeth or the 4 teeth, because those are odviously not symmetrical.
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abecedarian
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Re: stimulator board

Post by abecedarian »

The 'valley' between teeth is nothing more than empty space, and is typically where a VR sensor's output should be 0 volts. Nothing about the valley should be considered other than the period the wheel spends in the valley, and even then that is just a waiting period for the next tooth to come into the VR sensor's "window". When that happens, the voltage should swing positive, and as the center of the tooth passes over the center of the VR sensor, the voltage swings negative until the tooth has left the sensors "window", at which point the voltage should return to 0v, but as I've shown that's not always the case.

In the image you posted in your previous post, you "unwrapped" the trigger wheel, and have the distance between the teeth's root the same as the width of the teeth, but you forgot to take into account the difference in circumference between the 'root' of the teeth and the 'face' of the teeth, so no, they are not symmetrical given the heel and toe of the teeth are perpendicular to the face, and the circle created at the base of the teeth. Take some ink or paint and apply it to the faces of the teeth on that trigger, then roll it along some paper and you'll see what I mean.

No need to argue. I'm just pointing out some failed logic.
Last edited by abecedarian on Mon Aug 25, 2014 6:12 pm, edited 1 time in total.
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Re: stimulator board

Post by Sudo »

abecedarian wrote:The 'valley' between teeth is nothing more than empty space, and is typically where a VR sensor's output should be 0 volts. Nothing about the valley should be considered other than the period the wheel spends in the valley, and even then that is just a waiting period for the next tooth to come into the VR sensor's "window". When that happens, the voltage should swing positive, and as the center of the tooth passes over the center of the VR sensor, the voltage swings negative until the tooth has left the sensors "window".
I think the point went way passed your head. :o I already said that valley is useless in practice because we cannot detect the true point of zero crossing. And yes, the valley HAS A ZERO CROSSING. It is just not useful in terms of circuit design because we cannot reliably detect it

The point is, Russian is generating a 25% so that Honda thinks its more real. But in reality, that's much less real than 50%. That's the only failed logic I see.


Also, you CAN use the valley to trigger. Won't happen for the Honda distro, but something like this works:
Image

As you can see, Valley does have zero crossing. And it is in the center of the valley.
Last edited by Sudo on Mon Aug 25, 2014 6:26 pm, edited 1 time in total.
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abecedarian
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Re: stimulator board

Post by abecedarian »

Here's a trigger with just under 1mm wide teeth and valleys.
DSC00002.JPG
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Are you sure the distance between adjacent teeth is equal to the valley?

My micrometer says it's almost 3mm between teeth. That would result in about a 33% duty cycle between zero crossings.
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Re: stimulator board

Post by Sudo »

abecedarian wrote:Here's a trigger with just under 1mm wide teeth and valleys.
DSC00002.JPG
Are you sure the distance between adjacent teeth is equal to the valley?

My micrometer says it's almost 3mm between teeth.
This wheel will product zero crossing at the center of each teeth (maximum flux) and center of each valley (minimum flux). Period. That's pretty much the definition of VR.
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abecedarian
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Re: stimulator board

Post by abecedarian »

You have, in a round about way, proven exactly what I was saying.

With a toothed wheel, you're looking for the positive-going-negative transition; with a notched wheel, you're looking for the negative-going-positive transition. In either case, it's the sharp edge where the voltage swings quickly from one polarity to the other that is of interest, not the period between, where the voltage IS 0V.
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Re: stimulator board

Post by Sudo »

abecedarian wrote:You have, in a round about way, proven exactly what I was saying.

With a toothed wheel, you're looking for the positive-going-negative transition, with a notched wheel, you're looking for the negative-going-positive transition. In either case, it's the sharp edge where the voltage swings quickly from one polarity to the other that is of interest, not the period between, where the voltage IS 0V.
But that's wrong. ;) It happens in the center of the teeth where it switches from maximum positive flux to maximum negative flux. And vise versa for the valley where it switch from negative minimum flux to positive minimum flux. It does NOT happen at the edge of the teeth.

Image

Image

Image
Last edited by Sudo on Mon Aug 25, 2014 7:11 pm, edited 1 time in total.
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abecedarian
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Re: stimulator board

Post by abecedarian »

Did you notice that in the last picture, the VR sensor is obviously reversed?
Sudo wrote:
abecedarian wrote:You have, in a round about way, proven exactly what I was saying.

With a toothed wheel, you're looking for the positive-going-negative transition, with a notched wheel, you're looking for the negative-going-positive transition. In either case, it's the sharp edge where the voltage swings quickly from one polarity to the other that is of interest, not the period between, where the voltage IS 0V.
But that's wrong. ;) It happens in the center.
Image

Image

Image
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Re: stimulator board

Post by Sudo »

abecedarian wrote:Did you notice that in the last picture, the VR sensor is obviously reversed?
That's Irrelevant.

Point is:
Zero crossing happens in the center of the teeth where it switches from maximum positive flux to maximum negative flux. And vise versa for the valley where it switch from negative minimum flux to positive minimum flux. It does NOT happen at the edge of the teeth.
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Re: stimulator board

Post by Sudo »

I am going to beat this to death... Still need more convincing?
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abecedarian
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Re: stimulator board

Post by abecedarian »

Again, you've proven what I've said.

The tooth moves into the VR sensor "window" and the voltage swings (I suppose positive or negative is of little relevance), and as the center of the tooth passes the center of the sensor "window", the voltage swings to the opposite polarity. And that is the most reliable point for determining position. Pretty much exactly what I've been saying, and pretty much what the Maxim PDF doc screenshot you've posted says. Nothing about the valley is mentioned there, and that's what I've been saying- what happens in the valley, the void between teeth, doesn't matter... usually.

So here we have much ado about nothing. ;)
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Re: stimulator board

Post by Sudo »

abecedarian wrote:Nothing about the valley is mentioned there, and that's what I've been saying- what happens in the valley, the void between teeth, doesn't matter... usually.
The valley HAS a zero crossing point. THAT's what I am saying. It is near 50%. Just because we can't detect it electrically, doesn't mean it don't exist. So where in there do you see that 25% duty cycle to simulate a symmetrical VR signal is appropriate? All I am saying is that 50% is more appropriate.

I think I will let this one go. I give up. Think whatever you want. I am done :D
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abecedarian
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Re: stimulator board

Post by abecedarian »

Sudo wrote:
abecedarian wrote:Nothing about the valley is mentioned there, and that's what I've been saying- what happens in the valley, the void between teeth, doesn't matter... usually.
The valley HAS a zero crossing point. THAT's what I am saying. It is near 50%. Just because we can't detect it electrically, doesn't mean it don't exist. So where in there do you see that 25% duty cycle to simulate a symmetrical VR signal is appropriate? All I am saying is that 50% is more appropriate.

I think I will let this one go. I give up. Think whatever you want. I am done :D
The valley IS a zero crossing- that's where the tooth is leaving the VR sensor and the next tooth is approaching. Using that period for anything other than maybe running a timer to measure that period is pointless.
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Re: stimulator board

Post by Sudo »

abecedarian wrote:
Sudo wrote:
abecedarian wrote:Nothing about the valley is mentioned there, and that's what I've been saying- what happens in the valley, the void between teeth, doesn't matter... usually.
The valley HAS a zero crossing point. THAT's what I am saying. It is near 50%. Just because we can't detect it electrically, doesn't mean it don't exist. So where in there do you see that 25% duty cycle to simulate a symmetrical VR signal is appropriate? All I am saying is that 50% is more appropriate.

I think I will let this one go. I give up. Think whatever you want. I am done :D
The valley IS a zero crossing- that's where the tooth is leaving the VR sensor and the next tooth is approaching. Using that period for anything other than maybe running a timer to measure that period is pointless.
Both of the center of Valley and Teeth are zero crossing........... It depends on which one you choose. The one with more width is the less reliable one.
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abecedarian
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Re: stimulator board

Post by abecedarian »

Sudo wrote:Both of the center of Valley and Teeth are zero crossing........... It depends on which one you choose. The one with more width is the less reliable one.
And that typically is the valley.

So let's just let this lay in state. :D
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Re: stimulator board

Post by Sudo »

abecedarian wrote:
Sudo wrote:Both of the center of Valley and Teeth are zero crossing........... It depends on which one you choose. The one with more width is the less reliable one.
And that typically is the valley.

So let's just let this lay in state. :D
Exactly, so why are we purposely inducing a 25% signal? When in reality, it is at 50%?

My point is that our simulated VR signal using RS232 should follow "Real crossing point" (50% duty) for its transitions. Not the red signal (not 50%)...

Image
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Re: stimulator board

Post by kb1gtt »

Sudo wrote:But amplitude and the shape of the waveform are meaningless here. ONLY zero crossing matters.
I wanted to poke this comment a bit. The amplitude can give some information about RPM. However it's often not used. For example with chips that I have never seen, you could use the amplitude to change the band pass center frequency as a kind of kalman filter. Such a filter could be handy mostly for removing noise from the system when at low RPM. If you see a large amplitude spike when you expect a low amplitude spikes, you could ignore the spike as it has to be noise.

So how can this be applied to a simulator board? The simulator board should allow playback of the log file information. I agree that the MAX232 chip + and - ouput is better then several other options, and I also agree it can be better. For example, there are op-amps with differential outputs, that could be driven to make an exact match to the real signal. The goal with the MAX chip is that you play back a log file, and get the same TTL signals. Those TTL signals are handy for validating pieces of the system and allowing desktop development. The MAX232 chip is also low cost and easily bread boarded.

The problem that russian is seeing is most likely due to a wondering DC offset similar to the picture posted above with the "real 0 crossing" comment added. See modified picture below, notice the length of the noise in the middle is the source of the errors being detected. When that noise is short enough, it doesn't trigger the energy detected. However when the noise is there long enough, it triggers the energy dector and creates false triggers. It doesn't take much to bugger the VR signal.
7_27_10_raw_vr_vs_lm1815_output_NOISE_modified.jpg
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Sudo
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Re: stimulator board

Post by Sudo »

Yes, and by providing a 25% duty cycle signal instead 50%. The DC is not zero anymore because of the imbalance signal. The average is above zero in Russian's case. His signal looks like 75% high and 25% low, which result as a ~3V DC if the signal is +/-6V peak to peak. That's my point.

Russian, just try 50% for the 24 teeth signal. That way you can prove me wrong and I will just shut up about it. :D
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abecedarian
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Re: stimulator board

Post by abecedarian »

Am I missing something somewhere regarding what duty cycle means?

To me, a 25% duty cycle means during one period, 1/4 spent high, 3/4 spent low... 25% at 'high' voltage and 75% at the low voltage.
Thresholds obviously play a part in this as well, though.
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Re: stimulator board

Post by Sudo »

abecedarian wrote:Am I missing something somewhere regarding what duty cycle means?

To me, a 25% duty cycle means during one period, 1/4 spent high, 3/4 spent low... 25% at 'high' voltage and 75% at the low voltage.
Thresholds obviously play a part in this as well, though.
75% and 25% duty is interchangeable in my book. It is all matter of perspective. :D Just like how certain country design all of their circuit referencing the power instead of ground.

So if you insist, change everything from 25% to 75%. It's basically the same to me. All my ideas still applies. It would be -3V DC instead of +3V DC.

So for a 50% duty cycle, is it half high or half low? :lol: Ok, lame joke. Anyways. You get my point.
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Re: stimulator board

Post by AndreyB »

Status update: now with 1uF electrolytic capacitors, hopefully I've positioned all of the right.
RPM 300, x24 channel works fine:
3 digital inputs + 3 digital outputs
Image
ChA = max232 digital input, ChB = max232 analog ouput
IMAG001.BMP
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RPM1200, x24 channel is skipping:
Image
IMAG000.BMP
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Re: stimulator board

Post by AndreyB »

Now max232 analog output and VR digital output at 1200 and 2400.
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Re: stimulator board

Post by AndreyB »

Never mind, one of the caps was not where it should be. New picture with the cap in the right spot, 3600 this time
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Re: stimulator board

Post by AndreyB »

Now with a 1uF series / de-couping capacitor between MAX232 output and Honda VR input, 1200 is not skipping and 2400 is skipping 50%, not 75% as it used to. Progress!?
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Re: stimulator board

Post by AndreyB »

Now with a 1K low-pass resistor
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Re: stimulator board

Post by AndreyB »

Some more pics with some resistors between max and honda and honda and gnd.

Image
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Re: stimulator board

Post by kb1gtt »

Here are some ball park values for the max chip circuit with high pass filter. I used a 1uF cap as that's what used for the max chip, and then tuned to 500 ohms to get an eyeball equiv of a VR signal.
10ms-20ms_VR-simulated-signal.png
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Re: stimulator board

Post by AndreyB »

Just ordered rev 0.2

It did not matter so much for Oshpark, but for a larger run from China we need to shrink it into 10cm/3.93701 inches
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Re: stimulator board

Post by AndreyB »

This thread is a mess :( We have at least three? four? barely-related subjects here
1) the actual board initially created by @ and all the preceding discussions
2) VR stimulation in general and VR stimulation application to Honda OEM, mostly using the MAX232 chip
3) a failed (?) idea about using another interface chip for VR stimulation
4) "analog" signal generation if I call this right because see my signature.

If any of these would be continued I would really like to split it. Can someone please start a separate thread instead of responding but the #1 topic and I will do my best to move all the relevant messages into the new thread. Hopefully this would make sense for everyone? Last thing I want is to became an "on-topic" Nazi.
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Re: stimulator board

Post by AndreyB »

Image

No idea when I will solder this :(
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