Hall gear tooth sensor requirements

[Madkaw]

I am using this Hall sensor for my tach/rpm. I am powering it with the MS3x 5v tps. I have my flywheel drilled to a 36-1 pattern

http://www.cherrycorp.com/english/senso ... 1_1004.htm

Am I to follow the instructions below as per the manual to make changes on the MS3 board? The instructions call for the board to be set-up per a VR sensor, but typically Hall sensors are not called VR sensors-thus the confusion for me.
I am ready to test crank timing, but I have no rpms right now, but I did earlier with this sensor and no mods to the MS3 board-is that possible? If someone wants to explain trigger thresh hold to me, that would be appreciated




Gear Tooth sensor
The gear-tooth sensor is a variant of the hall sensor - the key difference is that it has a magnet built into it and switches when close to steel, no external magnets are required. This makes them very easy to use. These are almost exclusively a three wire sensor. In CAS (crank angle sensor) units a multiplug may be used to combine multiple sensors. The sensor itself acts like a switch to ground when close to steel. The gear-tooth sensor requires a supply voltage which is usually 12V from a fused 12V supply or 5V from the TPSREF output of the Megasquirt. The sensor is then grounded at the Megasquirt and the third wire connects to the tach input.

Typical use of geartooth sensor with steel trigger wheel.
When a steel tooth passes the sensor it grounds the output. (0V)
At other times, the output is inactive. (The pullup in the ECU will make this 5V.)

A commonly used sensor is the 1GT101DC from Honeywell. This is rated from -40C to +150C.

The Megasquirt board needs to be set for VR input. V3.0 VR+pullup setting - V3.57 VR+pullup setting
(Note, that previous Megasquirt versions may have used the optoisolator input, but for better high frequency response with toothed wheels and to match the input on the MS3X card, it is advised to use the VR circuit.)

The Megasquirt main board has provision to adjust the trigger threshold on the input signal - these is by two small potentiometers inside the case. These are labelled R52 and R56. Using a small screw driver, carefully turn both about 12 turns anti-clockwise. (There is no dead-stop, but you may feel a "click" when the end position is reached, they can't be damaged by turning too far.)) Then rotate R56 a few turns clockwise.

[DaveEFI]

Have you added the pull up resistor to the VR input?

[Madkaw]

No I haven't. My issue was properly identifying what my sensor is (VR or Hall) and to follow those instructions.
Are you refering to pads on R57?

[Madkaw]

Anyone? Very anxious to hear my engine run powered by my MS.

[cmonref]

The pullup resistor is shown on the diagram about mid-page on your sensor's website (see below.) It is installed between VCC (the 5v or 12v you supply to the sensor) and the signal going back to MS. Note the Ground is NOT connected to the pullup resistor. Without the pullup resister, the hall sensor will not send a signal to the MS and your engine will not run.

The pullup resister is not related to R57.
6g 22 AWG x 1m BBB


[The pullup resistor is between these two lines on your website. (The actual diagram did not copy.)]
Open Collector Sinking Block Diagram

[diagram showing pullup resistor is here]

Recommended Pull-up Resistor Values
Volts DC 5 9 12 15 24
[And look here for resistor values depending on what VCC you feed it.]

Brian

[Madkaw]

So are you saying that I do or do not have to make the changes on the 3.57 board as recommended on megamanual?

The pull up resistor at the sensor is still necessary even after making the board changes-correct?

[Madkaw]

Well never got a direct answer so I went ahead and dropped the unit off to make the board changes as stated above-hope I did right. I guess i will know in a couple of days-----really anxious

[billr]

Is the Megamanual even applicable to the V3.57 board? Do the directions there differ from this in the MS3 assembly docs?

V3.57 board - VR Input with pullup for hall sensors, GM LS2/58X, optical sensors or points
a) Find JP1 in the bottom right of the board. Place a jumper across positions 1 and 2
b) Find J1 in the middle of the board. Place a jumper across positions 3 and 4
c) Install a 1k resistor (any value 470R - 2k2 is likely ok) onto the pads marked R57
d) With a small screwdriver, turn the pots, R52 and R56, 7 turns anticlockwise (sometimes you may feel a "click" when the end position is reached, they can't be damaged by turning too far.) and then turn R56 back about 2 turns clockwise.

That all seems very simple and clear to me. Sorry I didn't reply before, I thought your question was in regard to how the drilling on the flywheel had to be (hole diameter, spacing, depth) rather than config of the V3.57 board.

[Madkaw]

The directions I copied were for the 357 board. Yes , maybe very simple but confusing all the same!
I was just looking for confirmation of what my research showed me.
Thanks

[kaeman]

I know what you mean, occasionally I get confused by the instructions also, but your board needs the pull up resistor because the vr/hall sensor needs it for a signal. From what I can figure out the vr and hall sensors react the same and as such they use the same settings.
Good luck.
how did you get the 36-1 hole pattern drilled into your flywheel, are you inverting the signal or something because drilling the flywheel would leave you with an extra high not the missing high where the missing tooth would be.
To un confuse me did you drill 35 holes? after making 36- 10 degree separated marks?

[billr]

I think the OP can simply switch the "input capture" from "falling edge" to "rising" (or the opposite) to account for a missing hole instead of missing tooth.

[Madkaw]

Yes , I simply drilled 35 holes in the flywheel. I will post up a picture when I am on my laptop. Drilled the 36th hole on the backside of the flywheel to keep things balanced.
Should get my MS3 back today to try out.

[Madkaw]

This is what I did-see pic. I guess the file is too big
I have rpms now! Now let's see how far off my tooth angle is;0

[DaveEFI]

To post a pic, put it on Photobucket, etc, then copy the direct link to your post to here. Highlight that link in your post and click on 'Img' and the pic will then appear in your post. But isn't actually uploaded to this site.

[Madkaw]

IT RUNS!

Did the appropiate changes to the MS 3.57 board and added a pull-up resistor to the sensor wiring. I also pulled my hall sensor to find that i adjusted it to close to my flywheel and it had scraps on the tip. I had an extra and wired it in with the pull -up resistor. Got my timing close enough I guess and she fired off after making sure the fuel was there.



thanks for the help guys-Ill back with more questions but this thread is done i hope

[walterclark1]

So are you saying that I do or do not have to make the changes on the 3.57 board as recommended on megamanual?

The pull up resistor at the sensor is still necessary even after making the board changes-correct?

You only need one pullup resistor in the circuit, either at the sensor OR on the mainboard (R57).

From: http://www.megamanual.com/357/index.htm

There is a unpopulated pull-up resistor on the tach input line (R57) that can be added to provide bias for Hall sensor and other input sources.

[cmonref]

You only need one pullup resistor in the circuit, either at the sensor OR on the mainboard (R57).

It was my understanding that R57 biases the board's circuitry and that a resistor at the hall sensor is still necessary to bias the sensor. Without that resistor, the hall sensor will not function and will not put out a signal for the circuitry to interpret. That is the way that my hall gear tooth sensor and MS3/3.57 are wired.

[walterclark1]

It was my understanding that R57 biases the board's circuitry and that a resistor at the hall sensor is still necessary to bias the sensor. Without that resistor, the hall sensor will not function and will not put out a signal for the circuitry to interpret. That is the way that my hall gear tooth sensor and MS3/3.57 are wired.

According to the schematic, that is incorrect. http://www.megamanual.com/357/ under Schematics R57 is directly on the Tachin line and ties Tachin to 5V thru a 1K resistor. It is electrically identical to the resistor that is wired into a V3 board to the VRIN line and 5V from the proto area and its purpose is to provide a pullup or bias to an attached Hall sensor or other sensor requiring a pullup bias to function.

[jsmcortina]

walterclark1 is correct.

James

[Madkaw]

WOW- you guys have my head spinning.

SO, other then the pull up resistor, was the megamanual instructions I copied correct for making the necessary board changes to use the Hall sensor?
I'm glad I can remove the resistor on the sensor wiring for a cleaner wiring job.