2nd Trigger Hall

czb83 · Post by **czb83** » Sun May 14, 2006 8:49 am

Hello, I was reading up on making wheel decoder/2nd trigger work. My vehicle has a hall crank and cam sensor, not VR. Does this mean I don't need to build that conditioner board, and I can hook the outputs directly up to U4 Pin6 and CPU pin 11? Do I still need a resistor inline with CPU pin 11?

If that is right, is that the only change needed. I have my MS setup for hall input right now, but then I realized I needed a second trigger to work with my setup. So now I'm looking a MSnSE to try and get it to work. Im not worrying about spark output right now, I'm just going to be testing for correct tach signal and then add spark after I get it running for a while.

Thanks,
Christopher

czb83 · Post by **czb83** » Mon May 15, 2006 2:06 pm

please?

Keithg · Post by **Keithg** » Mon May 15, 2006 5:43 pm

Well, I did exactly this. To do it, I used this schematic:

http://www.wideopenwest.com/~kgrider/saab/hall_schematic.pdf

Mine is a rotating magnet, so I used the top schematic, but used a pullup through a 22k resistor instead of the 12V through the 47k. The right end of this circuit is the processor pin.

thx for asking this as I forgot to document it on my web page.

KeithG

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czb83 · Post by **czb83** » Fri May 19, 2006 4:49 pm

Im sorry, but I still dont understand what to do. I don't understand this notion of "pullup" resistor either. So I have to hall sensors to connect. Would I connect one the normal way to input pin 24 on db37, or would it go to u4 pin 6, what is the difference. For the second input, it goes to pin 11 on CPU, but I make it run through a 47k resistor first. Is that correct?

Keithg · Post by **Keithg** » Fri May 19, 2006 7:52 pm

A 'sinking type' hall sensor will generally just provide a ground or no ground, not a hi/ground pulse train. MS needs a pulse train. To get this with most hall sensors you will need a pullup resistor to 'pull up' the lead to 5V or 12V when it is not grounded. The result is a pulse train when you pass a series of targets in front of the sensor. Onthe MSnS-E page dizzy setup, there is a simple test to detwemine if the hall sensor is a sinking type (most common - this needs a pullup resistor) ot a source type that puts out a pulse train.

The 2 schematics differ in that the one creates a 12V pulse train and the other creates a 5V pulse train. This schematic is connected to pin 11 for the second trigger. The crank sensor needs to be connected to pin24 DB37 and this input configured for a hall sensor like it states in the assembly instructions. The instructions do not mention teh need for a pullup resistor, but this will probably be needed here as well. I connected a resistor (1k) between the 12V source hole near the DB37 and the jumper at the bottom of the board on the opto in.

KeithG
KeithG

czb83 · Post by **czb83** » Sun May 21, 2006 10:16 am

I think I see now. So really, you could connect the 12V directly, but you use a resistor instead to stop feedback, is that correct? I thought I had read all the documentation, but I don't remember ever reading about things like this. Is this specific to MnSE? I just started getting into that after learning regular MS code could not work with my setup.

Thanks

Keithg · Post by **Keithg** » Sun May 21, 2006 10:59 am

you do not want to connect the 12V directly to the hall. the resistor is to reduce current draw through it when it is 'on', while still pulling it up to 12V when it is 'off'. This is standard EE at this point.

KeithG
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czb83 · Post by **czb83** » Sun May 21, 2006 11:40 am

Ok, I was going through the schematics for my vehicle to find info on my hall sensors. There are 3 wire: power/ground/out. They are powered with 8V. So does it matter what the voltage of the "pulse train" looks like. I assume if I wired up the 5V pullup that I would get a 8V/5V pulse train. This sound fine?

Keithg · Post by **Keithg** » Sun May 21, 2006 1:28 pm

well, the 8V is what the hall needs to power it up. A lot of hall sensors can be powered from 3-24V. This is the voltage required by the hall to conduct (like an NPN transistor) when a magnet is present. Look at is like this. When there is no magnet present (or when it is shuttered with the vane), it will float at some low voltage but not conduct. When the magnet is present (or uncovered) it will conduct to ground. With 12V and the resistor connected to 'o' on the hall sensor, it will be 12V on this lead until it conducts (no magnet), then it will be 0V (with magnet present). The 12V through the resistor is called 'pullup' because it causes this floating lead to be pulled 'high', in this case 12V. So, the hall is powered by 8V, but the pulse train will be 12V and 0V due to the pullup resistor (pulling it high until a magnet appears) then the hall pulling it to 0V (ground). You can use a 5V pulse train as well, but then you need to use alternate schematic 2 with the 5V pullup. It is pretty immaterial to the input circuit in the MS as it has an opto acting as a buffer between the ignition system and the processor.

All of this assumes that your hall sensor is a sinking type (all the Bosch ones I have used are as are most commercial ones I have used elsewhere). Some actually are source type. These put out a 12V (or some volt, 5?) when the magnet is present. Make sure to test it with a volt meter first to see which you actually have. If you look on the MSnS-E dizzy page, there is a pretty easy test you can try.

KeithG

On 5/21/06, czb83 <czb182@hotmail.com (czb182@hotmail.com)> wrote:

Ok, I was going through the schematics for my vehicle to find info on my hall sensors. There are 3 wire: power/ground/out. They are powered with 8V. So does it matter what the voltage of the "pulse train" looks like. I assume if I wired up the 5V pullup that I would get a 8V/5V pulse train. This sound fine?

This post is at: http://www.msefi.com/viewtopic.php?p=121349#121349

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czb83 · Post by **czb83** » Mon May 22, 2006 5:01 pm

Thanks for taking the time to help. Hopefully in a couple days I start setting this up and see if I get a good tach signal. I'm sure I'll be back with more questions ;)

czb83 · Post by **czb83** » Sun Jun 25, 2006 4:54 pm

Ok, I got help from a friend with an oscilloscope and we measured my crankshaft hall sensor. I have 12 windows on the wheel and for each window there was a 5V spike, and it was 0V base. So 0V with 12 5V spikes per revolution.

So, does this mean I need to use the first schematic to have 12V on no ground, and then it will drop down to 5V for each window? Or can I use the sensor input with no pullup? Thanks.

czb83 · Post by **czb83** » Mon Jun 26, 2006 4:57 pm

ok, based on this diagram

im guessing that I dont need a pullup resistor. Is this correct?

Keithg · Post by **Keithg** » Mon Jun 26, 2006 5:31 pm

I've had to have a voltage reference on all of my hall sensors. do the test. if it does not show a 0/5v or 0/12v pulse train, you will need a pullup.

KeithG

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czb83 · Post by **czb83** » Mon Jun 26, 2006 10:11 pm

the top graph is the crankshaft hall sensor, reading 5V at top and 0V at bottom. The bottom is the camshaft hall sensor.

czb83 · Post by **czb83** » Wed Aug 02, 2006 11:54 pm

Sorry to bring this back up, but I have this problem still and you seem really knowledgable about this sorta stuff.

That graph was the hall connected to the stock computer. The MS could read the hall signals as long as I spliced the connections between the two. If I connect the hall directly to MS I read no voltage. I guess I really do need a pullup. I was trying to figure out how it worked. I wired up 5V to the hall signal line with a 1k resistor. I read 5V but it flucuates a little when cranking. Is it perhaps that there is too much current going to hall and it cant change the voltage? Is this why the resistance on the pdf you had were so high? I'm going to try a 22k ohm resistor next time I go home, but wanted to know if my theory was right. Is there a way to determine how much resistance you should put? What if a put a variable resistor to it and watched it with a scope while changing the values? Not sure if I can find one that will work, but just trying to think of what I will do once I start working on it to save time. Any input would be greatly appreciated.