Hall effect sensor questions

shortbus

Joined Sep 30, 2009
8,703
Why do you assume I'm using coil packs?
Why do I assume that? Because you said it in your post #4.
The objective is to make an abomination with mechanical timing, but solid state switching and individual coils to

If the exact dwell were that important the coils wouldn't work at different speeds, since the dwell changes based on RPM, on top of that, the dwell depends on things that are easier to test than attempt to calculate using ideal numbers, like how long it takes for the sensor to react to the trigger signal it's supposed to be receiving, and how much dwell the specific coil actually needs in order to function.

Are you for real or just trolling? Dwell angle is a known thing no matter what the RPM is. And it is a measurable function of the rotation of and timing between the crank and camshaft. As the RPM increases the coil changes into more of a flyback circuit so it takes less time and energy to produce a spark.

Can I ask your age and automotive mechanical experience?
 

Thread Starter

l0vot

Joined Apr 29, 2013
107
Can you explain how each individual cylinder is receiving a spark pulse? It seems like the sensor would have to be turned on by a magnet signal for each cylinder. ... Something like the black disk in the picture here with multiple pole pieces.
View attachment 224020

One magnet, 4 sensors, 90° apart, since only one cylinder fires at one time, and each sensor is firing one cylinder, dual output coils can make this work for an 8 cylinder engine as well, since 4 cycle engines with an even number of cylinders operate the cylinders in pairs, one reaches TDC on the compression stroke, the other reaches TDC on the exhaust stroke, it's OK to fire on the exhaust, so one dual output coil can run 2 cylinders instead of 1 coil per cylinder. I'm not doing that because it also wears out the plugs faster, but it was pretty common before coil packs took over.20201203_215926.jpgThis is a crude mock-up of how the sensors will be positioned, I'm going to have to form the leads so I can solder them further away to stay clear of those screws, and still be as close to the magnet as they can reasonably be without getting hit by it, then do a live fire test to make sure everything is going to work, then probably use silicone to prevent the sensors from moving around, and fatiguing the leads. The vacuum advance arm goes under the circuit board (the gold colored bar), the centrifugal advance is in the body of the dizzy, it will advance the shaft the magnet is mounted on.
 

Thread Starter

l0vot

Joined Apr 29, 2013
107
Why do I assume that? Because you said it in your post #4.






Are you for real or just trolling? Dwell angle is a known thing no matter what the RPM is. And it is a measurable function of the rotation of and timing between the crank and camshaft. As the RPM increases the coil changes into more of a flyback circuit so it takes less time and energy to produce a spark.

Can I ask your age and automotive mechanical experience?
individual coils!= coil packs, they accomplish the same purpose, but aren't the same thing, assuming i was referring to coil packs is on you.

Dwell time doesn't need to be precise, dwell angle isn't precise, this is demonstrated perfectly by old points style systems, the nub, and contacts can wear, which does absolutly change the dwell angle, but it continues to work until the switch no longer reliably switches. The only advantage to pinpointing the dwell is reduced heat dissipation, since the coil, and it's driver are on for the bare minimum amount of time to do it's job, the minimum dwell is based on the exact coil, and driver circuit. I don't have the numbers to do the math to find the minimum viable dwell to make this setup work, you don't have those numbers, and since this project is a mashup of random components I thought would work together, I doubt any one person has those numbers right now. The only way to find the minimum dwell is to test this design, and see what happens, current bench tests demonstate that it does spark reliably under conditions similar to actual engine operating conditions, if I had a better scope, and a better test rig, I could pin down the minimum dwell, and maybe even integrate that information into the design, but I don't, so the dwell is probably going to end up a little longer than necessary, but the alternator certainly isn't going to miss a couple watts wasted due to the lack of optimization.

If you want this project done differently, do it yourself, I'm sure someone with as much experience as you can do a better job.

Building things and seeing how they work is how I learn, even if this doesn't work perfectly, mission accomplished.
 
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drc_567

Joined Dec 29, 2008
1,135
One magnet, 4 sensors, 90° apart, since only one cylinder fires at one time, and each sensor is firing one cylinder, dual output coils can make this work for an 8 cylinder engine as well, since 4 cycle engines with an even number of cylinders operate the cylinders in pairs, one reaches TDC on the compression stroke, the other reaches TDC on the exhaust stroke, it's OK to fire on the exhaust, so one dual output coil can run 2 cylinders instead of 1 coil per cylinder. I'm not doing that because it also wears out the plugs faster, but it was pretty common before coil packs took over.View attachment 224078This is a crude mock-up of how the sensors will be positioned, I'm going to have to form the leads so I can solder them further away to stay clear of those screws, and still be as close to the magnet as they can reasonably be without getting hit by it, then do a live fire test to make sure everything is going to work, then probably use silicone to prevent the sensors from moving around, and fatiguing the leads. The vacuum advance arm goes under the circuit board (the gold colored bar), the centrifugal advance is in the body of the dizzy, it will advance the shaft the magnet is mounted on.
... The orientation of the magnet has to be so that a particular flux direction hits the the branded sensor face, in order for it to work, according to fig. 3 of the datasheet. That is, if the magnet is fixed with the wrong pole outwards, then it might not work. ... Something to perform a test on before setting the magnet in place.
... It may be that the whole magnet is not necessary to activate the magnetic sensors. A carbide blade should be able to cut off some of the excess magnet so that any centrifugal force will be less likely to detach it.
 
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shortbus

Joined Sep 30, 2009
8,703
If you want this project done differently, do it yourself, I'm sure someone with as much experience as you can do a better job.
Just being a devils advocate.
You seem to want to reinvent a design that seemed to work for years. with only one coil and a distributor cap. Seemingly for engines that have brains /computers and no easy way of putting a distributor in it, again maybe reading into the things you have said.

individual coils!= coil packs, they accomplish the same purpose, but aren't the same thing, assuming i was referring to coil packs is on you.
Only some one who is doing this without knowing would go that way. Why wouldn't a coil pack be used? They last as long or longer than a old time round coil. And are cheaper and easier to find.
 

drc_567

Joined Dec 29, 2008
1,135
... Some years ago I installed the Heathkit version of this same device on a GM 8 cylinder 350 engine, ... a standard single coil in those days. The magnetic sensor must have been specifically designed for that application. There was no magnet to activate the sensor, but it was positioned so close to the corner edges of the octagonal distributor cam that every time a ferrous steel corner passed by the sensor the primary coil current was turned on. Then when the cam flat passed, the slightly greater sensor distance switched the current off and the secondary coil fired the spark. ...Not really sure about that. Maybe it was the other way around, with the coil current building up while the cam flat passed the sensor, and the spark occuring when the corner part went by the sensor face. For the next 15 or 20 years, it worked with no problems, until I finally sold it.
 
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shortbus

Joined Sep 30, 2009
8,703
The magnetic sensor must have been specifically designed for that application. There was no magnet to activate the sensor, but it was positioned so close to the corner edges of the octagonal distributor cam that every time a ferrous steel corner passed by the sensor the primary coil current was turned on.
Like the early cranckshaft and camshaft position sensors did. A PM wrapped in wire (like a guitar pickup) and made a pulse every time a steel or ferromagnetic object went by. The GM HEI pickup does the same thing, the reluctor is just iron and the magnet is in the HEI module. https://en.wikipedia.org/wiki/Crankshaft_position_sensor
 

Thread Starter

l0vot

Joined Apr 29, 2013
107
Just being a devils advocate.
You seem to want to reinvent a design that seemed to work for years. with only one coil and a distributor cap. Seemingly for engines that have brains /computers and no easy way of putting a distributor in it, again maybe reading into the things you have said.



Only some one who is doing this without knowing would go that way. Why wouldn't a coil pack be used? They last as long or longer than a old time round coil. And are cheaper and easier to find.
I wanted to change the points out for a magnetic pickup, and transistor because the mechanical points were giving me issues, and i want to know how everything on that engine works, inside, and out, any conversion was a black box, coil packs are a black box with unknown drive characteristics, and the exhaust would probably cook them since it's so close, then I figured go big, or go home, why not drive individual coils? interestingly, having the coil in the configuration I'm going to use with the hybrid distributor fixed all the problems the points were giving me, the engine runs better than it did with the dizzy with magnetic pickups, probably beacuse that dizzy was made for an engine with dual plugs, and the engine this is for has a single offset plug, so even though I could get the idle timing set properly, the timing advance probably wasn't nerly as aggressive as it needed to be, the older points based distributor was made for a very similar engine set up a very similar way, so it's a good match.
 

Thread Starter

l0vot

Joined Apr 29, 2013
107
... The orientation of the magnet has to be so that a particular flux direction hits the the branded sensor face, in order for it to work, according to fig. 3 of the datasheet. That is, if the magnet is fixed with the wrong pole outwards, then it might not work. ... Something to perform a test on before setting the magnet in place.
... It may be that the whole magnet is not necessary to activate the magnetic sensors. A carbide blade should be able to cut off some of the excess magnet so that any centrifugal force will be less likely to detach it.
the pulses were getting awful short in the test, I think it wants the whole magnet, the dizzy is going to be tested for function before gluing the magnet, it sticks well enough to spin it with a drill to make sure everything is working as it should.
 

shortbus

Joined Sep 30, 2009
8,703
I wanted to change the points out for a magnetic pickup, and transistor because the mechanical points were giving me issues,
The most common fix for things like that is a HEI module and the points. The module contanins all of the amplification and power drive so by using it the points only see a very small current through them. There are a lot of people doing this with how to do it online. Doing it with the HEI module is what I meant by a design that has worked for years.
 

Thread Starter

l0vot

Joined Apr 29, 2013
107
The most common fix for things like that is a HEI module and the points. The module contanins all of the amplification and power drive so by using it the points only see a very small current through them. There are a lot of people doing this with how to do it online. Doing it with the HEI module is what I meant by a design that has worked for years.
There are a lot of designs that work, but I wanted to build one myself, honestly I could have just strapped a transistor directly to the points system so the points would only need to switch the transistor instead of the entire coil, but that would be too easy, and I wouldn't learn anything.
 
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