How a Hall ignition works?

[DiegoVV]

Hello dear members,

I´v been trying to figure out how an Hall effect distributor works.

As opposite to a regular distributor in which the High Voltage is switched by the rotating contact against the fixed contacts in the distributor cap, the hall distributor operates based on switching a hall effect sensor.

Now my question:

For a 8 cylinder engine I will need 8 hall effect sensors and 8 HV sources.

How can you switch 8 different spark plugs with only one switch (hall sensor)?

You will need also 8 HV circuits for triggering the spark, each one associated to a separate hall sensor, isn´t it?

I thing a simple wiring schematic will help a lot. hehe

Thank you in advance

 

[stevehuckss396]

For an 8 cylinder engine you will need 1 sensor. You will need to turn the sensor on and off 8 times per rotation. The Hv will take the path from the center of the cap to which ever point the rotor is pointing to at that time.

The sensor can be turned on by a single magnet. A sensor and magnet are positioned with a steel rotor that spins between them. The steel rotor would have 8 windows in it so the magnet/sensor pair can "see" each other and turn the sensor on. You can also trigger it with 8 magnets.

 

[DiegoVV]

Thank you steve for your quick response.

The point I am not able to see is how with only one switch, distributor is able to choose where to send the spark.

If we have 8 cutouts in the distributor crown, we will trigger 8 sparks per cycle...that´s OK. But...how it is sended to each spark plug?

If the distributor is still switching on and off the HV, where is the advantage of this system? The key benefit of the hall sensor distributor type is to get rid of the HV direct switch...isn´t it?

Thank you!!

 

[tomrux]

Got it bunt to frack mate.

The hall effect unit takes the place of the switch/points in the low tension side of the circuit. The distributor, hence it's name, distributes the spark to the correct plug.

Tom R

 

[gbritnell]

http://auto.howstuffworks.com/ignition-system.htm

 

[Noitoen]

Only other way I know is to use 4 "double" ignition coils and 1 hall sensor with a sequencer circuit or 4 hall sensors to each coil. There will be a "miss fire" on each cylinder at the end of the exhaust cycle but without consequences.

I still think it's easier to build a distributor, at least for more than 2 or 4 cylinders.

 

[74Sprint]

Hall Effect distributors use 1 x magnetic source, 1 x metal windowed/shutter wheel with 8 windows, and 1 x Hall effect. So what they do is put a magnetic source usually an electric coil on one side of the shutter wheel and the Hall Effect on the other side. The Hall Effect turns off when a window comes by and on when a metal shutter comes by. The metal shutter extends the magnetic field to the Hall Effect. A rotor sits on top of all this to distribute the spark. The Hall Effect is just a on/off signal to the primary voltage circuitry. I’ve seen some distributors with 2 sets of windows/shutters that are used for coarse and fine signalling. Mind you one could use 2 sets of windows/shutters so that one signals spark and the other signals fuel injection. Also Hall Effects can be "N", "S", Uni-Pole, Bi-Pole, side layout, and end layout. If you put a magnet behind the Hall Effect it will detect metal like a gear tooth or the cam lobes on the old points system (Pertronics ?).

Ray

 

[TimTaylor]

Maybe I'm missing something - haven't had my coffee yet this morning.....

If this is a 4 stroke engine, wouldn't you only be firing 4 cylinders per revolution?

 

[mu38&Bg#]

http://en.wikipedia.org/wiki/Wasted_spark

 

[74Sprint]

Maybe I'm missing something - haven't had my coffee yet this morning.....

If this is a 4 stroke engine, wouldn't you only be firing 4 cylinders per revolution?

Correct but, your forgetting that we need 720 degrees of crankshaft rotation to fire all 8 cylinders. For every 720 degrees of crankshaft rotation the distributor turning at half the crank speed turns only 360 degrees. So to fire all 8 cylinders the crankshaft makes 2 revolutions and the distributor makes only 1 revolution. Also don't forget that the distributor is usually turned by the camshaft.

Ray

 

[74Sprint]

http://en.wikipedia.org/wiki/Wasted_spark

Where's the Hall effect distributor ? The question was how a Hall effect distributor works as compared to a regular points distributor.

Inorder for a wasted spark to work on a 3 cylinder and up 4 stroke you need 2 signals, one from the crank and one from the cam or some way to signal the start of the sequence. No distributor required with wasted spark.

Ray

 

[DiegoVV]

Thank you for all of your responses.

Now I will be able to sleep without having in mind distributors, sensors, spark plugs, timings and so on.....

 

[mu38&Bg#]

Sorry, Ray. That was for Tim Taylor above my post in reference to Noiten. The hall distributor setup was already explained well. I would have explained it as identical to a points distributor, but using a hall sensor instead of points.

It's easy to setup a pair of CDI ignitions to run off the crank with a four cylinder four stroke. This arrangement is often used on model aircraft engines. The sensors are 180° apart with one magnet on the crank. Each ignition fires a plugs on cylinders at TDC.

I've heard that the Saito 3 cylinder spark ignition engines also use wasted spark and fire all three cylinders at the same time. They use an four magnets on the crank and bipolar sensor to sort it out.

 

[74Sprint]

Sorry, Ray. That was for Tim Taylor above my post in reference to Noiten.

Oh ok I see now and I hope I didn't come across to strong.

I've heard that the Saito 3 cylinder spark ignition engines also use wasted spark and fire all three cylinders at the same time. They use an four magnets on the crank and bipolar sensor to sort it out.

I heard something somewhere that said the same thing but, I never checked it out.

Ray

 

[jack.39]

Neighbor had trouble with his minivan, old model, Mitsubishi engine, I took a look into his distributor. What a revelation! No Hall effect, the genius Japanese used an LED which shone light through moving windows, falling upon a photocell! I thought: This is NUTS! Dirty environment = failed spark.

The Hall effect is IMO far superior. Better yet, dump the whole distributor, with it's mechanical faults: bearing wobble, not perfectly accurate timing, etc. In engines having long camshafts, the "wrap-up" of the stick causes variation in the timing of the spark, especially if the distributor is mounted at the far end (non-drive end) of the camshaft.

"Distributorless" has become standard nowadays. The computer is a far more accurate and consistent "Spark Master" than any previous system.

Just my 2 cents. jack

 

[TimTaylor]

Correct but, your forgetting that we need 720 degrees of crankshaft rotation to fire all 8 cylinders. For every 720 degrees of crankshaft rotation the distributor turning at half the crank speed turns only 360 degrees. So to fire all 8 cylinders the crankshaft makes 2 revolutions and the distributor makes only 1 revolution. Also don't forget that the distributor is usually turned by the camshaft.

Ray

Yeah, I know that... was thinking crank rotation, not distributor....like I said, hadn't had my coffee yet this morning. ;D

And dieselpilot, thanks for the link!

 

[TimTaylor]

"Distributorless" has become standard nowadays. The computer is a far more accurate and consistent "Spark Master" than any previous system.

Just my 2 cents. jack

I like the idea...pretty simple electronics, you wouldn't even need a computer. Two sensors would be required - one to tell you when#1 cylinder is at TDC and the 2nd to provide a similar signal for the other cylinders

You would still need either a coil for each cylinder (OK, for each pair of cylinders if wasted spark is used) or a way to switch the output of a single coil to the appropriate cylinder.

 

[jack.39]

I like the idea...pretty simple electronics, you wouldn't even need a computer. Two sensors would be required - one to tell you when#1 cylinder is at TDC and the 2nd to provide a similar signal for the other cylinders

You would still need either a coil for each cylinder (OK, for each pair of cylinders if wasted spark is used) or a way to switch the output of a single coil to the appropriate cylinder.

Given that a computer is in use, all that's really needed is TDC #1 cylinder, and appropriate programming. Ford still used a distributor in it's 5.0L V-8s until their end, around '95 in Mustangs. (Explorers had the 5.0 for several years after, but I think they went distributorless). The distributors had a rotating steel "cup" with notches cut out. As the "teeth" passed the sensor, a pulse was generated. One tooth was wider than the rest: #1 cylinder!

It's possible to generate each cylinder's spark at the right time by simply knowing TDC #1 instantaneously (almost), and given that provides accurate crankshaft speed, the appropriate time interval, or number of pulses counted, determines subsequent spark times. Gets a bit hairy.

The really neat thing about distributorless is the ability to constantly vary spark advance in order to obtain maximum fuel economy. Then, a "knock-sensor" constantly, and also nearly instantaneously, inputs the PCM just as advance reaches the edge of spark knock, and advance decreases slightly. All this is going on while driver-demand is ever-changing engine speed and load! The little electronic brain never gets overworked! jack

 

[TimTaylor]

Jack,

I understand all that. You still need more than one pulse per revolution to measure the rpm for the purposes of controlling when to fire each cylinder. In industrial vibration analysis we often use a single pulse per revolution to establish rpm, but that is for the primary purpose of establishing an index reference for doing phase related analysis, not for control. When doing things like tortional vibration analysis, we use on the order of 60-100 pulses or more per revolution to get the resolution we need.

My context was referring to using this technology in a model engine ignition application.While you could do it with a single sensor as you describe, it would require a relative fast microcontroller and some sophisticated software to do the pulse width measurement and comparison.

By contrast, with two sensors I could do the majority of the logic in a relatively simple PGA - spark advance, etc. could be done with very little additional circuitry.

Tim

 

[74Sprint]

For a low parts count, simple (sort of), and programmable CDI for small engiines of 1 or 2 cylinder you can check out my thread on RC Groups.
Programmable Open Source CD Ignition PIC1840
http://www.rcgroups.com/forums/showthread.php?t=1781959

It's not setup for more than 2 cylinder right now but, it will be later. It can run on 4.8v to 18v.

Ray