Cam signal idea for full sequential
#61
Both inputs of the scope are set to DC, so they are showing you the absolute voltage on the line at any given time. At the left, the green 1> icon shows you the 0V point for channel 1. It is quite clear that the signal coming from the VR sensor is positive with regard to ground for half of the cycle, and negative with regard to ground for the other half.
Do you contend that the waveform shown in channel 1 is not an AC sine wave?
Do you contend that the waveform shown in channel 1 is not an AC sine wave?
Your contention was that if you move the 0v line to the bottom of the sine wave you still have an ac signal...which you don't because all the voltages are above 0v.
You might still get a signal with one of the probes on the negative shield wire but the proper signal is your negative probe on one signal wire and your positive probe on the other signal wire (because that is what the PCM sees).
I will be out vacationing for the next couple days, see you all later.
#64
Boost Pope
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Let's go back and look again at what we both said:
Originally Posted by Joe Perez
It's not until you connect the sensor to an input circuit that you really define a reference. Typically, one side of the sensor is connected to ground.
The only wiring that goes to ground on a vr sensor is the shield wire, not the signal wires.
What I started out with was that the VR sensor, by itself, is a device generating a balanced output signal (one where the voltages on the two wires are always of equal but inverse magnitude) and that this voltage is not referenced to anything at all except for the other leg, until such time as one of the two legs is connected to a common point. Typically, this common point is the ground point of whatever circuit is being used to receive the signal from the other wire.
You then replied that connecting one side of a VR sensor to ground causes it not to generate "the expected ac sine wave."
I then posted a scope trace showing the output of a VR sensor which has one leg connected to ground, where you can see that the output is an AC sine wave.
What am I missing here?
#65
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IOW, all electrical potentials are relative to a reference point.
#66
Yes yes, and it's all -10,000v relative to some van degraff generator located in toledo. The important thing is that it's centered on the refernce voltage - i.e. the peak differential between on leg and the other.
Of course, little of that matters for this guy - I'm still a fan of buying a $0.50 sensor, putting it by the gear, and glueing a magnet like you would a bicycle. :-) OEMs do this, so it's not unreasonable.
Couldn't you look at falling edges and get the same information, PLU... no, I guess you need even spacing, eh?
Of course, little of that matters for this guy - I'm still a fan of buying a $0.50 sensor, putting it by the gear, and glueing a magnet like you would a bicycle. :-) OEMs do this, so it's not unreasonable.
This is one reason why the MS1 cannot do full sequential, as its trigger inputs are edge-detecting only and require all edges to be evenly spaced. So we ignore the trailing edge, read the leading edge of CMP (which has a fixed relationship to CKP) and use it to reset the cycle counter.
#67
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You know, I just realized something- you could easily implement this in hardware! Put CMP and CKP into an AND gate, and do a one-shot on the gate output's falling edge. That would give you the ability to do four-channel ignition with MS1. (Still no four-channel injection.)
#68
It's all down to if the software will know what to do with it.
You're the guy who loves assembly, why not dive in there and fix it? :-)
More seriously, yes, I'm a fan of doing it in hardware, if the software can take advantage of it, that seems like a sweet, simple set up. As would be griding off all the teeth till you're down to one, which is what you are doing, no?
You're the guy who loves assembly, why not dive in there and fix it? :-)
More seriously, yes, I'm a fan of doing it in hardware, if the software can take advantage of it, that seems like a sweet, simple set up. As would be griding off all the teeth till you're down to one, which is what you are doing, no?
#69
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Largely because I have no CAS, and I've gotten to the point where I'm starting to think about the next car rather than the current one. If all goes to plan, that one will be running MS3.
Huh?
As would be griding off all the teeth till you're down to one, which is what you are doing, no?
#71
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Well, you're basically masking from the CPU all but one pulse of the cam, right?
#73
Guys,
Been working nights and just catching up. Some great stuff here. Can someone summarise (for a non-electrical engineer) the options for me? Simplicity and reliability are the key requirements. Got some time off coming up and getting the car sorted is one of the things I'll be doing during that time.
Been working nights and just catching up. Some great stuff here. Can someone summarise (for a non-electrical engineer) the options for me? Simplicity and reliability are the key requirements. Got some time off coming up and getting the car sorted is one of the things I'll be doing during that time.
#74
All,
I am going the Hall route on EMs advice. It turns out that the studs on the FM adjustable cam gears are stainless steel. What I need to do is replace one of the nuts with a mild steel version and, apart from mounting the sensor, I should be good to go.
I do require a little help though. The FM cam gears don't use metric studs. I think they are UNC, but can't be sure. Can anyone on the other side of the pond tell me or find out what thread they use so I can try and source the correct nut?
I'll post up the results once the engine is running. Should be done by the end of the week.
I am going the Hall route on EMs advice. It turns out that the studs on the FM adjustable cam gears are stainless steel. What I need to do is replace one of the nuts with a mild steel version and, apart from mounting the sensor, I should be good to go.
I do require a little help though. The FM cam gears don't use metric studs. I think they are UNC, but can't be sure. Can anyone on the other side of the pond tell me or find out what thread they use so I can try and source the correct nut?
I'll post up the results once the engine is running. Should be done by the end of the week.
#75
Hall? a true 'hall effect' sensor is a magnetic sensor, it looks for a voltage crossways to a current flow, and will be happy to ignore unmagnetized teeth, mild or otherwise.
The stock miata "hall" sensor is not a hall sensor, it's a VR sensor. Personally, I'd take that, grind off two teeth from a stock (or stock-compatible) cam gear, and you'd be done.
The stock miata "hall" sensor is not a hall sensor, it's a VR sensor. Personally, I'd take that, grind off two teeth from a stock (or stock-compatible) cam gear, and you'd be done.
#76
Hall? a true 'hall effect' sensor is a magnetic sensor, it looks for a voltage crossways to a current flow, and will be happy to ignore unmagnetized teeth, mild or otherwise.
The stock miata "hall" sensor is not a hall sensor, it's a VR sensor. Personally, I'd take that, grind off two teeth from a stock (or stock-compatible) cam gear, and you'd be done.
The stock miata "hall" sensor is not a hall sensor, it's a VR sensor. Personally, I'd take that, grind off two teeth from a stock (or stock-compatible) cam gear, and you'd be done.
Unfortunately I don't have a stock compatible cam gear to grind off any teeth. These are teeth on the stock intake cam gear?
#77
Yes, the 99+ gears all have teeth on them, two on one end, a single on the other.
They are pretty much using utterly garbage terminology. :-) A hall sensor litterally looks for a magnetic field. Some sensors have a magnet inside, then when metal goes by (mild steel) it warps the field from it's own internal magnet and reads that. Then there are "VR", or 'variable reluctance' sensors, which due a similar trick, but don't use the Hall effect to read the signal.
In practice, people often say "hall" effect for a sensor which puts out a digital, or near digital (technically an "open collector output", which grounds a wire every time the sensor is sensing something) signal. Sometimes these are processed hall signals, sometimes processed VR signals, for that matter it could very well by optical.
As to the bolt, can't you just drill/tap the gear for any bolt you have handy?
If you want a stock '99 gear, with the teeth on it, I could mail you one for the cost of shipping, no problem, but you should be able to get a junkyard one much cheaper.
-Abe.
Note the righthand gear (exhaust), there's a single tooth on bottom, and a double on the top.
They are pretty much using utterly garbage terminology. :-) A hall sensor litterally looks for a magnetic field. Some sensors have a magnet inside, then when metal goes by (mild steel) it warps the field from it's own internal magnet and reads that. Then there are "VR", or 'variable reluctance' sensors, which due a similar trick, but don't use the Hall effect to read the signal.
In practice, people often say "hall" effect for a sensor which puts out a digital, or near digital (technically an "open collector output", which grounds a wire every time the sensor is sensing something) signal. Sometimes these are processed hall signals, sometimes processed VR signals, for that matter it could very well by optical.
As to the bolt, can't you just drill/tap the gear for any bolt you have handy?
If you want a stock '99 gear, with the teeth on it, I could mail you one for the cost of shipping, no problem, but you should be able to get a junkyard one much cheaper.
-Abe.
Note the righthand gear (exhaust), there's a single tooth on bottom, and a double on the top.
#78
Yes, I see the teeth on the cam gear now. I probably have one stuffed in a box somewhere as the stock gears were removed when the head was built.
Seeing as we are talking sensors, here is the sensor I will be using.
Whether I use a small magnet (6mm diameter button) countersunk into the gear (and epoxied) or change one of the stainless steel studs/nuts for a ferrous set will depend on where I can effectively mount the sensor. I hope to drill the plastic shroud and mount through that, otherwise I'll have to fabricate something out of aluminium to mount it in front of the cut off cam cover section. I favour the magnet idea at the moment.
Seeing as we are talking sensors, here is the sensor I will be using.
Whether I use a small magnet (6mm diameter button) countersunk into the gear (and epoxied) or change one of the stainless steel studs/nuts for a ferrous set will depend on where I can effectively mount the sensor. I hope to drill the plastic shroud and mount through that, otherwise I'll have to fabricate something out of aluminium to mount it in front of the cut off cam cover section. I favour the magnet idea at the moment.
#79
Maybe put a stud in one and leave it longer? The sensor does look for ferrous metal, not a magnet. A magent would likely work, if the polarity is right.
DealExtreme: $2.36 Super-Strong Rare-Earth RE Magnets (8mm 20-Pack) Maybe there? They have lots of sizes, but it was the smallest I've seen.
BTW, I put a magnet into the head of a bolt on my car cause I got tires of dropping that bolt. It wasn't hard to do, just found a magnet which matched the bolt and put a drop of (probably unneeded) glue. It's the sort of like that.
McMaster-Carr I wonder if somethign like that would work. I've seen 'bungee nuts' which are just nuts with a tall metal top for hooking bungee cords on motorcycles. Anything like that might give you your pulse.
DealExtreme: $2.36 Super-Strong Rare-Earth RE Magnets (8mm 20-Pack) Maybe there? They have lots of sizes, but it was the smallest I've seen.
BTW, I put a magnet into the head of a bolt on my car cause I got tires of dropping that bolt. It wasn't hard to do, just found a magnet which matched the bolt and put a drop of (probably unneeded) glue. It's the sort of like that.
McMaster-Carr I wonder if somethign like that would work. I've seen 'bungee nuts' which are just nuts with a tall metal top for hooking bungee cords on motorcycles. Anything like that might give you your pulse.
#80
You know I never considered the magnets polarity. Actually how would one check it was correct?
I have ordered a few of these magnets. EM feel a magnet might be a little strong forcing me to run a large gap, so I may go back to the idea of replacing a stud and nut with ferrous items (I think I have found a machine screw and nut that fits, no idea what the thread actually is though).
I have ordered a few of these magnets. EM feel a magnet might be a little strong forcing me to run a large gap, so I may go back to the idea of replacing a stud and nut with ferrous items (I think I have found a machine screw and nut that fits, no idea what the thread actually is though).