Looking for a reluctor interface. - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 09-26-2010, 07:58 PM   #1
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default Looking for a reluctor interface.

I'm looking for a simple circuit to read my ABS sensors without interfering with the operation of my ABS system. I need to convert the AC from the mag sensors into a 5v square wave like a hall effect sensor would put out. It appears that I need a reluctor interface with a high impedence floating input (neither input grounded). The megasquirt kept coming up as I was searching for a circuit. It looks like it can be built with a VR reluctor interface for reading cam/crank mag sensors? Does this circuit have a floating input? If so, can it be lifted from a diagram so I can build one?
DammitBeavis is offline   Reply With Quote
Old 09-26-2010, 08:06 PM   #2
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,915
Default

MAX9924.

I used this chip in my new crankwheel decoder. It's awesome and also has a differential input. Build the circuit as per the mode A2 reference schematic in the datasheet, and it's just plug-n-play.

Joe Perez is offline   Reply With Quote
Old 09-26-2010, 08:24 PM   #3
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

Well ****, Amazing! Thanks!
What's the best way to prototype with those surface mount components. I've never messed with components that wouldn't stick into a breadboard.
DammitBeavis is offline   Reply With Quote
Old 09-26-2010, 08:32 PM   #4
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,915
Default

Here's how I did mine:



The little adapter board was just a few dollars, and if you're not comfortable doing SMC, they will even mount your chip for you.

Source thread: https://www.miataturbo.net/megasquirt-18/max9924-47243/



It's a damn shame they didn't use this chip on the new MS3X board; that would have been a fabulously simple, reliable, highly versatile way to go.

Or did they?

We'll never know, since the schematic is a closely-guarded secret inaccessible to us mere mortals.

Last edited by Joe Perez; 09-26-2010 at 08:46 PM.
Joe Perez is offline   Reply With Quote
Old 09-26-2010, 09:30 PM   #5
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

That's just in-*******-credible. Everything I need from a pair of 9926 chips for $5. Then $8 for two of those breakout boards. The ($8 ?) assembly charge for one of those boards sounds like a great alternative to screwing around for 2 hours with an iron. I'll have less than $40 invested in a 4-channel reluctor interface!

Looking at your scope captures, I could probably use 100K resistors on the input side and still get a reliable output.

What size caps are you using to filter the power supply?

Thanks again!
DammitBeavis is offline   Reply With Quote
Old 09-26-2010, 10:07 PM   #6
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,915
Default

Quote:
Originally Posted by DammitBeavis View Post
What size caps are you using to filter the power supply?
The ones they specify in the documentation. 10nf, .1uf, and 1uf. I also tossed in a 10uf, just out of habit. The small ones I soldered directly to the backside of the carrier.
Joe Perez is offline   Reply With Quote
Old 09-27-2010, 06:43 AM   #7
Senior Member
 
Join Date: Nov 2007
Location: Belgium
Posts: 939
Total Cats: 59
Default

A propos, c'est le poulet et la poule
WestfieldMX5 is offline   Reply With Quote
Old 09-27-2010, 11:59 AM   #8
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

FYI, Proto-Advantage quoted me $11.99 per adapter with assembly, and $2.97ea+$10 shipping for the MAX9926 chips.

So 4-channels worth of VR Interfaces on DIP adapters and ready to mount for $39.92 + Shipping!

They recommended that I sample the chips and ship direct to them to save a few bucks.

Edit: Shipping was free from Maxim to Proto for the samples, So the TOTAL cost for the first two was $23.98 + $4.00 Shipping.

Last edited by DammitBeavis; 09-27-2010 at 12:35 PM.
DammitBeavis is offline   Reply With Quote
Old 09-27-2010, 12:23 PM   #9
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,915
Default

Sounds good. The 9924/9926 really are incredible devices. If you look through the other thread I linked do, there are scope traces where you can see the chip pulling signals out of noise that renders them virtually invisible and producing reliable outputs every time. Just amazing.


One word of advice: when I got mine, I sampled them as well, and they took half of forever to get here. Maybe now that there's stock in the US it'll be different.


So, the big question: What the hell are you building?
Joe Perez is offline   Reply With Quote
Old 09-27-2010, 12:37 PM   #10
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

I need to feed the signals from my ABS sensors into my ECU to setup traction control.
DammitBeavis is offline   Reply With Quote
Old 09-27-2010, 12:51 PM   #11
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

I really only need 3 channels. One for each front wheel, then driveshaft speed for the driven wheels. The ECU can use Min, Max, or Average the speed of the two front wheels for accurate readings in turns. I'm putting in a **** to select off, dry, or wet tables. In each table I can define per-gear slip limits and how aggressively I want it to cut power. It should be fun to play with.
DammitBeavis is offline   Reply With Quote
Old 09-27-2010, 12:53 PM   #12
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,915
Default

Quote:
Originally Posted by DammitBeavis View Post
I'm putting in a **** to select off, dry, or wet tables.
Jeremy Clarkson would approve of this. Just make sure that the "off" position has some bizarre, incomprehensible acronym such as "CST".
Joe Perez is offline   Reply With Quote
Old 09-27-2010, 01:04 PM   #13
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

Quote:
Originally Posted by Joe Perez View Post
Jeremy Clarkson would approve of this. Just make sure that the "off" position has some bizarre, incomprehensible acronym such as "CST".
I prefer random colors. Right now my Launch control switch is white, ALS is yellow, fan override is black, and logger is red. If I label it at all, I think maybe green/blue/grey dots? It's even funnier since I'm red/green colorblind.
DammitBeavis is offline   Reply With Quote
Old 09-28-2010, 11:16 AM   #14
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

OK, since that last problem was so easy to solve...... so I'll ask another thats a bit more difficult.
Is there a chip that will take two pulsed inputs, and average them into one pulsed input? I guess it would need 2 frequency counters, add them together, divide them by 2, and generate a square wave at the target frequency.
DammitBeavis is offline   Reply With Quote
Old 09-28-2010, 11:48 AM   #15
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,915
Default

Quote:
Originally Posted by DammitBeavis View Post
Is there a chip that will take two pulsed inputs, and average them into one pulsed input?
Yes. It's called a microcontroller.

(An FPGA would probably also work.)
Joe Perez is offline   Reply With Quote
Old 09-28-2010, 12:08 PM   #16
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

I was looking at an Arduino. With a proper microprocessor doing some math, I could integrate a yaw and accelerometer sensor (I already have a BOSCH sensor box from an STI DCCD system) to get accurate relative wheelspeed in a turn. Then I could feed the ECU an 'ideal' slip ratio.
DammitBeavis is offline   Reply With Quote
Old 10-01-2010, 04:34 PM   #17
Junior Member
Thread Starter
 
Join Date: Jan 2007
Location: EXTREME Southern Illinois
Posts: 281
Total Cats: 0
Default

The assembled boards shipped today. That was fast! They recieved the sample chips and assembled the boards 4 days after ordering.
DammitBeavis is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
FS: RARE pair of Mazda blank VVT camshafts MiataRoadster MiataRoadster 0 09-21-2013 02:55 PM
traction control tapping into abs lines skir Suspension, Brakes, Drivetrain 15 07-15-2013 08:29 PM
MS Assembly Help schema MEGAsquirt 7 02-15-2012 12:07 PM
Vi-pec V44 Stand alone ECU pnp MIATA platinum Miata parts for sale/trade 1 10-27-2011 03:32 PM
Cam Sensor Output image wanted drgoodwrench ECUs and Tuning 10 01-08-2009 11:30 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 11:21 AM.