Abe & JasonC's NB Cam & Crank input circuits
#1
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After putting a bunch of time into cleaning up this drawing for a thread over at msextra.com, it occurs to me that it never did get stickied here. Prolem solved:
![](http://img37.picoodle.com/img/img37/4/5/27/thraddax/f_Abes2m_a6b73d2.gif)
Note that it's been suggested that the TL082 opamp may yield better performance than the LM393. The two are pin-compatible, so if possible you should attempt to substitute a TL082 in this circuit instead. The TL082 is available from RadioShack as P/N 276-1715, so this is one more thing in its favor.
As drawn, this is for MS2. You could use it for MS1 as well, by changing JS10 to JS8 on the B-side output.
![](http://img37.picoodle.com/img/img37/4/5/27/thraddax/f_Abes2m_a6b73d2.gif)
Note that it's been suggested that the TL082 opamp may yield better performance than the LM393. The two are pin-compatible, so if possible you should attempt to substitute a TL082 in this circuit instead. The TL082 is available from RadioShack as P/N 276-1715, so this is one more thing in its favor.
As drawn, this is for MS2. You could use it for MS1 as well, by changing JS10 to JS8 on the B-side output.
Last edited by Joe Perez; 05-04-2009 at 04:02 PM. Reason: Fixed image
#3
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If you are careful about your layout, it will easily fit into the proto area of the 3.0, with plenty of space left over for a couple of relay drivers. Abe was good enough to do a nifty 3d layout of the assembled circuit:
![](http://abefm.smugmug.com/photos/359141699_sJRfL-M.jpg)
Of course, you can if you wish to it on a seperate board, as etnad is doing:
![](http://img26.picoodle.com/img/img26/3/9/2/f_DSC02386m_ee98ebe.jpg)
(note that I do not condone this hideous mess of resistors. Are you listening, etnad? Clean up your goddamn wiring!)
When I abandoned the CAS and went to a wheel, I actually built the new decoder circuit in such a way that it is completely external to the MS, which made it easier to fine-tune. It's in a small external box, which tethers to my MS via a 3 wire cable as seen here: https://www.miataturbo.net/forum/sho...884#post251884
![](http://abefm.smugmug.com/photos/359141699_sJRfL-M.jpg)
Of course, you can if you wish to it on a seperate board, as etnad is doing:
![](http://img26.picoodle.com/img/img26/3/9/2/f_DSC02386m_ee98ebe.jpg)
(note that I do not condone this hideous mess of resistors. Are you listening, etnad? Clean up your goddamn wiring!)
When I abandoned the CAS and went to a wheel, I actually built the new decoder circuit in such a way that it is completely external to the MS, which made it easier to fine-tune. It's in a small external box, which tethers to my MS via a 3 wire cable as seen here: https://www.miataturbo.net/forum/sho...884#post251884
#5
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I decided to put it in an external box since I has just been through a very frustrating experiance with my previous ignition trigger circuits, and I wanted something that was easy to remove, test and modify if need be. As it turns out, it failed horribly the first time, but worked perfectly thereafter, once I flipped one connection around and re-installed it.
But the vast majority of folks build their pickup circuit right on the main board, regardless of what type of circuit it is.
#8
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Uhm... ****. I honestly don't know- I never bothered to steal his wallet and check his drivers license.
Abe, have I been mis-spelling your name all this time?
Abe, have I been mis-spelling your name all this time?
#10
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Oh, I was responding top Y8s' question about the spelling of his name, You snuck in right before I hit send.
What do you mean by "the bottom one"? The 3d rendering?
What do you mean by "the bottom one"? The 3d rendering?
#12
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Oh yeah. I remember that day well. We were coming around a big, fast turn, and I was trail-braking. Initially started heading for that wall, then over-corrected, spun 180, and exited the road backwards into those trees which, thankfully, stopped me without doing too much damage to the car.
Shortly thereafter I became a bit more serious about my tires and suspension. Needless to say, the T1Ss went away, as did the AGXs, the big rear bar, etc...
Shortly thereafter I became a bit more serious about my tires and suspension. Needless to say, the T1Ss went away, as did the AGXs, the big rear bar, etc...
#15
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This circuit was the result of Abe reverse-engineering the input circuits in his OEM '99 ECU. It is not an attempt at optimization, merely an exact duplicate of the factory circuit.
Delay due to the input filtration can be negated in software, as there is a specific field for entering the hardware latency of the trigger input.
Delay due to the input filtration can be negated in software, as there is a specific field for entering the hardware latency of the trigger input.
#20
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It's also been postulated that, even for an NA, this circuit is likely more reliable than the ones commonly used for 4G63 input. A number of NA owners (myself included) have found that CASs which worked perfectly on the stock ECU exhibited severe problems when used with a MegaSquirt. I'd like to see the next person who runs into that problem try this circuit.