DIY_EFI Digest Tuesday, 23 April 1996 Volume 01 : Number 118 In this issue: Honda ULEV Accord EX and linear air-fuel ratio sensor Re: Honda ULEV Accord EX and linear air-fuel ratio sensor Re: MCS48 cross-assembler? 68CH916X1 and 68F333 Ignition questions Re: MCS48 cross-assembler? What is a Hall Effect Sensor. See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: "Zublin, Bryan (SD-MS)" Date: Mon, 22 Apr 1996 09:44:00 -0700 (PDT) Subject: Honda ULEV Accord EX and linear air-fuel ratio sensor An article appeared in the August 1995 issue of Car and Driver that discusses the Honda ULEV Accord EX, or "ultralow emissions vehicle" for California. It sounds like the linear air-fuel ratio sensor is currently being used in the Civic VX, and that the same sensor will be used in the Accord ULEV. And if it is really a $300 option, then the sensor might be a low cost alternate to the existing wide range O2 sensors. Has anyone looked into exactly what the Honda sensor can do? Here is an excerpt: "Finally, the ULEV vehicle manages to keep extremely precise control over the air-fuel ratio, with the help of Honda's linear air-fuel ration sensor (LAF), an engineering windfall from Honda's now extinct Formula 1 racing program that was first used in the lean-burn Civic VX. When the engine is warm, the system changes the air-fuel ratio from lean to within a hair of stoichiometric, where catalyst efficiency is greatest for reducing the three major tailpipe pollutants. "For this mixture-control job, Honda employs an engine-control computer twice as powerful as the one in the standard Accord. To tightly monitor the air-fuel ratio for each cylinder, Honda could have inserted four LAF sensors in each exhaust manifold port, but that would have been too expensive. Instead, engineers discovered that with intensive use of control theory, the computer could be made to reliably calculate each cylinder's ratio by comparing the nuances of the single LAF (placed at the merge point in the exhaust manifold) with known ignition data. "This ULEV Accord will probably not be available until the fall of 1997, and Honda is still exploring how to sell it to the public. Mass-produced, it could go out the door as a $300 option." Bryan Zublin bzublin@xxx.com ------------------------------ From: Land Shark Date: Mon, 22 Apr 1996 14:07:28 -0600 Subject: Re: Honda ULEV Accord EX and linear air-fuel ratio sensor At 09:44 AM 4/22/96 -0700, you wrote: >And if it is really a $300 option, then the sensor might be a >low cost alternate to the existing wide range O2 sensors. Has anyone looked >into exactly what the Honda sensor can do? It is .. and it is used on all 1.5l VTEC Hondas... cost between $160 and $320!! I'm trying to get SOMEONE to help out with a UEGO driver circuit, and then I will do all the footwork to get the thing figured out ... Simply put .. Hondas "LAF" is a pumping cell sensor just like an NTK/Horiba UEGO sensor ... we just need the circuits .. ALL YOU SAE members, START DIGGING in the SAE Journals and books!! Jim Conforti ------------------------------ From: Donald Whisnant Date: Mon, 22 Apr 1996 17:23:03 -0700 Subject: Re: MCS48 cross-assembler? > >From: cmorris@xxx.com (Charles) >Date: Sun, 21 Apr 1996 07:27:15 -0700 >Subject: MCS48 cross-assembler? > >I'm in the process of building an additional injector controller, which >uses an Intel 8748 microprocessor. Since hand-coding is a real PITA, >does anyone know where I can find an assembler which runs on a PC? > >Thanks, >- -Charles Charles... TASM is a great assembler package for both 8x48 and 8x51 series hardware. It is downloadable for free via circuit cellar at 203 871-1988. Circuit Cellar does have a website (http://www.circellar.com) but they don't have those files available for ftp yet, so you'll have to call their direct board. Good luck on the controller... Donald Whisnant dewhisna@xxx.com ------------------------------ From: Darrell Norquay Date: Mon, 22 Apr 96 21:10:00 MDT Subject: 68CH916X1 and 68F333 To all you Motorola hackers out there... Motorola has recently announced their new Flash EEPROM chips in the HC16 and '332 lines. Some details: 68F333 - 32 bit Single Chip uController - 64K on board Flash EEPROM in 16 and 48K blocks - 4K byte SRAM - 16 Channel configurable TPU (Time Processing Unit) - On chip SCIM (Single Chip Integration Module) - 8/10 bit ADC - QSM (Queued Serial Module) 68HC916X1 - 16 bit Single Chip uController - 50K bytes Flash EEPROM, 16K and 32K modules, 2K Block Eraseable - 2K SRAM - General Purpose Timer - SCIM - 8/10 bit ADC - QSM Sound like some nifty devices, especially with the onboard Flash. There is also a special deal on the development kit for these two processors. Part number is MEVB1632 and it includes: - one base platform with either 68F333 or 68HC916 CPU "personality modules", (or BOTH :) - two free sample CPU's with kit - on-board Flash/MCU programmer - on board support for additional RAM/EPROM - integrated assembly/editing/evaluation/programming environment - in circuit debugger / Background Debug Mode - seven software breakpoint types - 2 RS232 comm links - logic analyzer pod connectors for all MCU pins - prototyping area and lists for $499 US. This is REAL CHEEP for what you get, less than half of list price after offer is over... Limited time offer until June 28, '96. Get 'em while they're hot! Available thru Electro Sonic, Future Electronics, Arrow/Schweber Electronics, Hamilton Hallmark, or Wyle Laboratories. Motorola Lit. Dist Center - 1-800-441-2447 Internet: http://freeware.aus.sps.mot.com MFAX: (data sheets and app notes) FAXback - 602-244-6609 (need TT phone) RMFAX0@xxx.com (email) regards dn - -- - ----------------------------------------------------------------- Darrell A. Norquay Internet: dn@xxx.ca Datalog Technology Inc. Voice: (403) 243-2220 Calgary, Alberta, Canada Fax: (403) 243-2872 "Absolutum Obsoletum" - If it works, it's obsolete - ----------------------------------------------------------------- ------------------------------ From: Darrell Norquay Date: Mon, 22 Apr 96 21:25:14 MDT Subject: Ignition questions Doug Rorem wrote: > Well this art isn't much better, but here's where you want to place > your fast recovery diode (switches on from a reverse bias condition > very quickly).. This provides a path for the current to keep flowing > in the coil after the transistor turns off [the coil wants to keep current > constant]. Without something like this, the coil can create very large > voltages and cause the transistor to break down. First, to reply to Doug's comments. I tried this years ago with an old points style ignition. I figured if I hung a fast recovery diode across the coil, as you've indicated, it would allow the coil's magnetic field to collapse faster, and induce a higher secondary voltage. As a side benefit, it should have absorbed most of the voltage spike from the primary and made the points last a lot longer as they wouldn't arc over as much. WRONG! It didn't work. As soon as I connected the diode across the coil, the engine stopped dead. As near as I could figure, what was happening was that all the energy stored in the coil was being dumped into the diode instead of being allowed to excite the secondary. With the diode, you're limiting the negative voltage developed across the primary to under a volt (the diode forward voltage), so even with a turns ratio of 100:1, that still only allows a secondary voltage of about 100V - definitely not enough to tickle a plug. So, the only way to get the coil to work properly is to allow the primary back EMF to increase at will. Clamping it to a small value will simply kill the output of the coil. The easiest way to protect the coil driver transistor is to simply turn it back on if the coil back EMF increases beyond a certain value. This can be accomplished by putting a couple of 150V or 200V zeners in series from the transistor collector back to the base, with a suitable current limiting resistor in series with the base to avoid pumping too much current into it. (this will destroy the transistor as surely as exceeding it's VCEO rating) This will allow the primary back EMF to go up to 300 or 400 V, then the zeners will begin to conduct and turn the transistor back on, thus limiting the back EMF to the value of the zeners. If you use a 500 or 600V 15A transistor, it should live quite nicely for a long time. But, you say, won't turning the transistor back on start charging the coil again and kill the spark? Yes, but the primary will take some time to build up to this voltage, and hopefully your spark has already triggered by the time the transistor turns on again. Also, the energy stored in the primary is relatively low, and it will only supply the base current of the transistor for a limited amount of time, as soon as the voltage on the primary drops below the 300 or 400 V threshold, it will turn off again. By this time, most of the stored energy in the coil will have dissipated and it will be ready for the next ignition charging sequence. Secondly, on the subject of ballast resistors, someone mentioned using a transistor driver with the existing coil and ballast resistor. This amounts to simply replacing mechanical points with a transistor, and in fact a lot of the earlier "electronic" ignition systems did this. (most noteably the Dodge little silver box with a wierd 5 pin plug) While this is certainly an improvement over points, it has little effect on the energy supplied by the ignition system. The ballast resistor is used as a current limit for the coil, and it was usually a big honking ceramic body resistor with a rating of a couple of hundred watts. The disadvantage of the ballast resistor approach is that, while it limits the maximum coil current, which protects the coil from self destructing, it also limits the charging current to the coil and increases the necessary dwell time significantly. This also limits the maximum energy stored in the coil, and ignition energy drops dramatically at higher RPM's because there is simply not enough time for the coil to charge to full capacity. With the later electronic ignitions, such as GM's HEI, there is no ballast resistor, and the coil has full unlimited current as soon as the module turns on. The coil quickly charges up to full capacity, and THEN an electronic current limit in the module kicks in to limit current to a safe value for the coil. This has the effect of reducing necessary dwell time, and giving much better ignition energy and performance especially at higher RPM's. Most of these use Motorola's MC3334 chip (or equivalent), and it's still the cheapest and best solution for a coil driver. It has all the necessary smarts built in to control a coil, including automatic dwell adjustment, current limit, mag pickup preamp, etc, an it's cheep! The coil driver transistor itself will be the most expensive part in the system. The newer modules use a different approach tailored to computer control, the Allegro Microsystems ULQ2460 is one such device with similar circuitry to the 3334, but with additional pins for computer control of dwell and timing. Check out the DIY_EFI web page for schematics of one system using the MC3334. This circuit is pretty much right out of the Motorola App Note. Note that the schematic has an error, however, the current sense resistor is missing. (my apologies to the author if it has been corrected). regards, dn - -- - ----------------------------------------------------------------- Darrell A. Norquay Internet: dn@xxx.ca Datalog Technology Inc. Voice: (403) 243-2220 Calgary, Alberta, Canada Fax: (403) 243-2872 "Absolutum Obsoletum" - If it works, it's obsolete - ----------------------------------------------------------------- ------------------------------ From: Chuck Mancuso Date: Mon, 22 Apr 1996 21:07:09 -0700 Subject: Re: MCS48 cross-assembler? At 17:23 4/22/96 -0700, you wrote: >> >>From: cmorris@xxx.com (Charles) >>Date: Sun, 21 Apr 1996 07:27:15 -0700 >>Subject: MCS48 cross-assembler? >> >>I'm in the process of building an additional injector controller, which >>uses an Intel 8748 microprocessor. Since hand-coding is a real PITA, >>does anyone know where I can find an assembler which runs on a PC? >> >>Thanks, >>- -Charles > >Charles... > >TASM is a great assembler package for both 8x48 and 8x51 series hardware. >It is downloadable for free via circuit cellar at 203 871-1988. Circuit Cellar >does have a website (http://www.circellar.com) but they don't have those files >available for ftp yet, so you'll have to call their direct board. > >Good luck on the controller... >Donald Whisnant >dewhisna@xxx.com > > > You can also get it from this URL: http://jcsm.com/html/category.htm It's version 3.0, about 142K. wmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwm || Chuck Mancuso || i i || || AEC Control Systems || {|} {|} || || Sandpoint, ID USA || {{|}} {{|}} || || chuckm@xxx.com || {((|))} {((|))} || || || {{{{|}}}} {{{{|}}}}|| || || ____|______________________|____|| wmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwmwm ------------------------------ From: Dennis Date: Tue, 23 Apr 1996 02:10:35 -0400 Subject: What is a Hall Effect Sensor. Hi Everyone, I'm kind of new here but I have been reading a lot of the posts and I would like to ask a question or two. :) A long time ago I read someone say that you can pick up the magnet in a speedometer if you have a hall effect sensor. I am trying to make something of a wheel possition sensor for class to measure the rotating speed of the wheel. I wanted to make it easy to install on different vehicles. I would like to know if you can buy a hall effect sensor or what is the particular design so that I might build one. As I understand it, they are just magnetic coils set up in a daisy fassion around a magnet rotating on the end of a circular object. The coils generate a positive or negative voltage due to the magnetic field generated, and it is the voltage of zero that is measured that tells just when the magnet passes the coil. Is this right? And does the magnet in a speedometer turn at 1:1 ratio with the drive wheel? Thanks in advance, Dennis Espinoza(Grad Student at California State University Northridge) ------------------------------ End of DIY_EFI Digest V1 #118 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".