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Old 06-10-2011, 01:20 PM   #1
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Default What kind of output does the NB speed sensor give?

I am having issues getting my NB speed sensor to work with my racepak dash. I was running a driveshaft pickup before (magnet/sensor) from some random aftermarket company but it was destroying the output seal on the tranny and had a mind of it's own on when it wanted to work.

I was under the assumption that I could get the NB sensor to work as the racepack will take any pulsed input from I think 2-10v and can use it. The main difference here is the NB sensor has two wires and the pickup I had only had one. Since I don't have the wiring on my car for the NB sensor, I can't figure out if one wire is a 5V or switched 12V signal or something and the other wire is a ground or the trigger wire? There is only provisions on the racepak for one wire for the speed sensor.

Any help with getting this set up? Do I need to give it 12V, 5V? Ground?

Thanks...
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Old 06-10-2011, 01:25 PM   #2
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it closes to ground
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Old 06-10-2011, 02:23 PM   #3
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OK, so I give it power and the wire that goes to the dash is a ground? Any idea if it will take 12v switched? Or am I going to have to wire in a resistor.
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Old 06-10-2011, 02:46 PM   #4
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Megasquirt typical input would be 2.2K pullup resistor to 12V and then a 10k from the sensor to the input.
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Old 06-10-2011, 03:13 PM   #5
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IIRC the NB sensor is not hall effect is it a VR. It needs to be conditioned by the mc in the stock gauge cluster, that also converts it to a square-wave type (12V high).
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Old 06-10-2011, 03:46 PM   #6
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ok, so then how would you suggest I set it up?

http://www.racepak.com/downloads/pdf/udxrpmanual.pdf
read page 6. It says it will accept a hall effect and "sine" wave sensor?
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Old 06-12-2011, 01:30 AM   #7
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Any tips from the techy people? Kinda sketchy driving around with no speedo... lol

How would a variable reluctor compare to the sine wave or hall effect that the dash accepts? The way I am reading it, is the signal changes when it gets faster rather than the sensor just pulsing faster?

http://www2.electronicproducts.com/H...2000-html.aspx

Do I need a signal converter of some sort? AC to DC?

http://www.msextra.com/doc/ms3/ignition.html



Quote:
In order to use a VR sensor a "conditioner" circuit is required to convert the AC voltage into a DC square wave signal while retaining the timing information. The Megasquirt board (V3 or V357) has this conditioner built in. One wire from the VR sensor is connected to ground at the Megasquirt and the other connects to the tach input. Ideally use a screened twisted pair cable. If fitted, connect the screen to ground at the Megasquirt end only.
Yeah it's MS info but I would assume the idea is the same?

Last edited by falcon; 06-12-2011 at 01:55 AM.
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Old 06-12-2011, 01:58 AM   #8
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Quote:
Originally Posted by y8s View Post
Megasquirt typical input would be 2.2K pullup resistor to 12V and then a 10k from the sensor to the input.
from what I've read, the MS has a built in conditioner circut.
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Old 06-14-2011, 12:58 AM   #9
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FML.... anyone?

Can someone build me the MS circut with the POTS on a seprate board? Pretty please.
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Old 06-14-2011, 01:49 AM   #10
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Old 06-14-2011, 12:32 PM   #11
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I dont think you need the pots.

try copying the input circuits on the left with the 12V pull up:



Your sensor goes on the left side. the right side goes to the ECU port/pin.
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Old 06-14-2011, 05:06 PM   #12
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Another solution I may have found is trying a 4 pin GM HEI module. It apparently converts the AC sine wave from old coilpacks to DC square for use in a tach on old GM cars or something.

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Old 06-14-2011, 05:07 PM   #13
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Quote:
Originally Posted by y8s View Post
I dont think you need the pots.

try copying the input circuits on the left with the 12V pull up:



Your sensor goes on the left side. the right side goes to the ECU port/pin.
I'll try that. My neighbor has a breadboard and all kinds of parts I can fiddle around with to try and get the right circuitry.
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Old 06-14-2011, 05:14 PM   #14
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Quote:
Originally Posted by Reverant View Post
IIRC the NB sensor is not hall effect is it a VR.
This.

I can absolutely guarantee you that the NB speed sensor is a cylindrical VR sensor, with an internal magnet. If you hook it up to a scope and spin it by hand, it generates an AC waveform.

Thus, it requires no pullup.

You could try using the MS's VR input circuit (sans pullup), or if you want something that doesn't suck, do this: https://www.miataturbo.net/megasquirt-18/max9924-47243/

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Old 06-14-2011, 05:17 PM   #15
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Well I just got off the phone with Racepak and talked to one of the programmers. He said the VR sensor "should" work if you just hook it up as is. He said their sensor produces up to 90v in the upper RPMS. I knew the dash accepted a sine wave signal, but I didn't know if it would take the really high volts the VR signal can produce at high RPMS. I'm going to hook it up and give it a try. I'll report back.

He said I shouldn't blow anything up, so if I do I recorded the convo :P.
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Old 06-14-2011, 06:37 PM   #16
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Just to confirm... blue with the yellow stripe is 12v, yes? Blue with the white stripe is the trigger input?
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Old 06-14-2011, 10:12 PM   #17
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? Anyone? I am looking at pin outs here and I'm not quite getting it. The only other blue white stripe wire I see is for a tach?

The sensor is in and wires routed into the car, I just need this last tidbit of info before I can go test it. Should I give it a full 12V or a 5V signal from my ECU?
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Old 06-17-2011, 04:21 AM   #18
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I just installed a Cyberdyne digital speedometer in a '99. The speedo has one wire for the speed signal and I tapped into the orange VSS wire on the back of the instrument cluster. Before I hooked it up, I checked it with a voltmeter (I didn't have a scope handy but remembered Joe's nice screenshots). On AC mode, it showed about 5V at low speeds and climbed from there so it looked like I had the right wire. Ran it in the air Ferris Bueller-style up to 80 and it works great!

Hope that helps.

--Bryan
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Old 06-18-2011, 02:24 AM   #19
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Are you sure it was AC? I though that wire on the back is already converted to DC square wave to feed the ECU. The converter is built into the dash. I don't have a stock cluster, just running the racepak. I tried it out the other day and set the racepak to read sine wave but it still dosen't work. Going to double check that the sensor isn't bunk.

Ordered a GM HEI to try out from my local parts monkeys.
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Old 06-18-2011, 02:31 AM   #20
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No, not sure it's AC, but DC mode wasn't showing me much. I don't have a scope here to check it out but I can look again with the voltmeter in a couple days before I close it all up.
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