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Old 06-24-2009, 02:39 PM   #21
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Originally Posted by y8s View Post
you have a 99 head... do you no longer have the front of the cam cover?
No, but I am hoping there is enough left to fabricate a stable mount for the sensor. See here and here.
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Old 06-24-2009, 03:08 PM   #22
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It should be fine, glue a magnet on.

My friend chopped his cover pretty bad, we got the OEM sensor back on... But you want a hall and a magnet I would think.
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Old 06-24-2009, 05:46 PM   #23
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It should be fine, glue a magnet on.

My friend chopped his cover pretty bad, we got the OEM sensor back on... But you want a hall and a magnet I would think.
If I were to use a sensor other than that supplied by EM I would need to check that it would provide the correct signal. Not sure what I need right now, but glueing a magnet on is an attractive idea. How small could it be? IOW I'd want to upset the balance of the cam gear as little as possible.

Thinking along similar lines could I use the standard EM mag sensor and a thin steel steel 'sheet' glued on there? How small and thin could the sheet be? Would the studs passing nearby result in interference? Any electrical engineer types out there or anyone with the right equipment to test this kind of idea?
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Old 06-24-2009, 06:06 PM   #24
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You might have to do a little signal tweaking, but I don't think it would be a big deal. I'm not sure how hard it would be to fake a VR signal, and I guess you don't want to do soldering in your case?

If you don't mine, then, I'd pull the gear, drill a hole in it, glue the magnet into the hole (should offset the weight a bit, you could even put a bolt on the opposit side for balance but I don't think you'll need to bother. It could be inboard of the adjuster bolts for minimal unbalancing.)


I guess the first thing to figure out is if it's a VR sensor for sure, or a hall. If it's a hall it's putting out a processed signal anyway. My guess would be VR though.

Anyone think we could take a hall signal, put an offset on it, and use the same "zero crossing" input from his VR sensor?
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Old 06-24-2009, 07:26 PM   #25
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You might have to do a little signal tweaking, but I don't think it would be a big deal. I'm not sure how hard it would be to fake a VR signal, and I guess you don't want to do soldering in your case?

If you don't mine, then, I'd pull the gear, drill a hole in it, glue the magnet into the hole (should offset the weight a bit, you could even put a bolt on the opposit side for balance but I don't think you'll need to bother. It could be inboard of the adjuster bolts for minimal unbalancing.)


I guess the first thing to figure out is if it's a VR sensor for sure, or a hall. If it's a hall it's putting out a processed signal anyway. My guess would be VR though.

Anyone think we could take a hall signal, put an offset on it, and use the same "zero crossing" input from his VR sensor?
Soldering I don't mind (although for wiring connections I prefer crimp terminals).

I like the magnet in the cam gear idea. I have to take all this apart some time soon as I want to fit an ATi damper. Where to source a suitable small magnet from though? Also I am not sure what parts (sensors) I would need to make this idea work.
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Old 06-24-2009, 08:13 PM   #26
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I'm pretty sure any old strong magnet would work. Some rare earth. The sensor will likely have a spec. Hmmm. I wonder if SparkFun would have something like this?

Digi-Key - 620-1185-1-ND (Allegro Microsystems Inc - A6850KLTR-T)

SparkFun Electronics - Dual Axis Magnetic Sensor Eval Board - Honeywell HMC1052L

But probably something from McMaster would make more sense. Honestly, I'd get one off the distributor of an 80's dodge. They used Hall sensors for exactly this application, these speeds, these temperatures.

SparkFun Electronics - Photo Interrupter CNZ1120 A tall bolt would work with this well.

Digi-Key - 620-1045-ND (Allegro Microsystems Inc - A3230LUA-T)
This is basically what you want. There's tons of signals out, but you want a power, ground, signal, and just glue/bolt it inside the cover, call it good.

Edit: Interesting, that last one is designed for ring magnets - i.e. you could use a round magnet on the face of the gear, instead of a single embeded spot. Personally, I like the single dot idea, but it's a way to go. You'd get a rising edge on one cycle, and falling on another.
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Old 06-25-2009, 02:24 AM   #27
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The TEC will accept a 0-5V signal for the cam sync.
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Old 06-25-2009, 03:08 AM   #28
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FWIW, Toda cam gears have a steel insert on tye backside to trigger the NB sensor. I stumbled across a pair of these one off gears ebay a few years ago. The hubs were on 90-97 gears initialy so I had a friend machine an NB gear for the hub on the intake side.
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Old 06-25-2009, 08:28 AM   #29
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Originally Posted by AbeFM View Post
I'm pretty sure any old strong magnet would work. Some rare earth. The sensor will likely have a spec. Hmmm. I wonder if SparkFun would have something like this?

Digi-Key - 620-1185-1-ND (Allegro Microsystems Inc - A6850KLTR-T)

SparkFun Electronics - Dual Axis Magnetic Sensor Eval Board - Honeywell HMC1052L

But probably something from McMaster would make more sense. Honestly, I'd get one off the distributor of an 80's dodge. They used Hall sensors for exactly this application, these speeds, these temperatures.

SparkFun Electronics - Photo Interrupter CNZ1120 A tall bolt would work with this well.

Digi-Key - 620-1045-ND (Allegro Microsystems Inc - A3230LUA-T)
This is basically what you want. There's tons of signals out, but you want a power, ground, signal, and just glue/bolt it inside the cover, call it good.

Edit: Interesting, that last one is designed for ring magnets - i.e. you could use a round magnet on the face of the gear, instead of a single embeded spot. Personally, I like the single dot idea, but it's a way to go. You'd get a rising edge on one cycle, and falling on another.
Thanks for the links. Trouble is I'm not familiar with electronics so I'd need an idiots guide to how to set this up to reliably generate the sync signal for the TEC. At the moment I suspect that it is beyond me.
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Old 06-25-2009, 08:30 AM   #30
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FWIW, Toda cam gears have a steel insert on tye backside to trigger the NB sensor. I stumbled across a pair of these one off gears ebay a few years ago. The hubs were on 90-97 gears initialy so I had a friend machine an NB gear for the hub on the intake side.
So this is just a stud/steel insert on the cam gear for the NB cam sensor to read? I wonder if that NB sensor generates a TEC friendly signal? I presume Mazda sell them for a price?
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Old 06-25-2009, 11:04 AM   #31
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So this is just a stud/steel insert on the cam gear for the NB cam sensor to read? I wonder if that NB sensor generates a TEC friendly signal? I presume Mazda sell them for a price?
That's a stock NB cam gear outer, fit onto an aftermarket inner hub which is where the adjustability is.

You see the two raised bumps at the top of the outer section and the one raised bump at the bottom (by the white dot)? Those are part of the OEM casting, and they're what the cam sensor reads in the '99-'00.
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Old 06-25-2009, 12:34 PM   #32
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Thanks for the links. Trouble is I'm not familiar with electronics so I'd need an idiots guide to how to set this up to reliably generate the sync signal for the TEC. At the moment I suspect that it is beyond me.
Why not use a factory NB sensor? Just use one magnet in the right position, feed it 12V (or is it 5V?), voila!
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Old 06-25-2009, 12:38 PM   #33
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Why not use a factory NB sensor? Just use one magnet in the right position, feed it 12V (or is it 5V?), voila!
TEC I believe feeds +5v to the sensor (easy enough to check) - anyone know what the NB sensor requires?

If it is +5v then I just glue a small magnet to the cam gear, add a factory NB sensor to the recipe and the TEC will see a signal that it likes?
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Old 06-25-2009, 01:33 PM   #34
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should be 12V as it is fed straight from the main relay terminal D.
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Old 06-25-2009, 06:58 PM   #35
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Why not use a factory NB sensor? Just use one magnet in the right position, feed it 12V (or is it 5V?), voila!
I could be mistaken, but I was pretty sure that sensor sees the same +5V the TPS sees. I don't think I'm feeding +12 into my little circuit.


Also, the miata sensor is a VR sensor, not a hall sensor. It "emulates" hall sensor output (i.e. the conversion to digital is done in the sensor, hence the 5V feed), but it's actually a VR.

But hall sensors are not hard to find. I listed one which should work just fine, and number of those will work.
-Abe.
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Old 06-25-2009, 09:59 PM   #36
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I could be mistaken, but I was pretty sure that sensor sees the same +5V the TPS sees. I don't think I'm feeding +12 into my little circuit.
+12, straight from the main relay:



Output is open-collector.
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Old 06-25-2009, 10:27 PM   #37
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thanks guys for doubting me.
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Old 06-25-2009, 10:40 PM   #38
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So this is just a stud/steel insert on the cam gear for the NB cam sensor to read? I wonder if that NB sensor generates a TEC friendly signal? I presume Mazda sell them for a price?
That's not a Toda in the picture. Its some home brewed one off that I found on ebay. Very well machined, made from good materials and cad plated. Trusted it enough to put on the car. What caught my eye on the original NA pulley was the adjuster disc being inside the circle of the timing nubs so I could copy the modified outer with an NB gear to take advantage of that. Makes cam timing changes on the dyno easier if you're using the OEM hall sensor.
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Old 06-25-2009, 11:55 PM   #39
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What year CAS are we talking here?

The CAS from 1990-1997 outputs two separate signals to drive the injectors and ignition coils.

One signal is a square wave 0-5v. The other if I remember correctly is an analog ac type signal.

There is no VR sensor in a Miata CAS from 90-97

The VR sensor is on the OBDII cars from 1996 on...but that is at the crankshaft, not the CAS.

I am going to look through my waveforms and see if I have a CAS signal. If I don't I will get some and post them here.

Last edited by mrtonyg; 06-26-2009 at 10:21 AM.
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Old 06-26-2009, 04:19 AM   #40
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What year CAS are we talking here?
....
The VR sensor is on the OBDII cars from 1996 on...but that is at the crankshaft, not the CAS.
WE're talking '99 cars, no CAS at all. The VR crank sensor (with the open "hall" output), and a similar one on the cam.


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Output is open-collector.
Oh, yeah, that about explains in. Funny, I remember something not working right when I have my 5v ref messed up, but maybe it was something else. Obviously it was.
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