ssave@ole.UUCP (Shailendra Save) (05/30/91)
I am trying to get a signal from the drive shaft of my car using an inductive pickup. (To calculate and display speed) Before I get under and get dirty, I wanted to know if anyone has had any experience with a similar transducer? Can you recommend one? The car being a big hunk of metal, and the tolerances between the "magnet" and the pickup being of the order of 0.2 in., will it work? Any related ideas? Sometime ago, I asked the net about a weekend project to make a tachometer for my car. I got numerous replies, for which I am thankful. Hopefully I will soon have a complete digital dash. I will post a summary for those interested. Shailendra ssave@caen.engin.umich.edu sumax!ole.uucp!ssave
vbreault@rinhp825.gmr.com (Val Breault) (05/30/91)
In article <1970@ole.UUCP>, ssave@ole.UUCP (Shailendra Save) writes: > > I am trying to get a signal from the drive shaft of my car > using an inductive pickup. (To calculate and display speed) > Before I get under and get dirty, I wanted to know if anyone > has had any experience with a similar transducer? Can you > recommend one? The car being a big hunk of metal, and the > tolerances between the "magnet" and the pickup being of the > order of 0.2 in., will it work? > > Any related ideas? There's a lot of stuff happening under your car. Stones, water, vibration, dust. Then too, the driveshaft will wobble several thousandths on it's spline. Rather than attempt to make something that will work in that rather hostile environment, why not try this idea? In the days before automotive computerization, a cruise control setup consisted of a mechanical device that was attached via flexible cable between the transmission and speedometer. You should be able to get one of these pretty cheap at a nearby junk yard (oops, 'Automotive Recycler'). It will contain all the necessary parts (bearings, etc.) to make the mechanical part of the project pretty easy, as well as getting it up into the engine compartment, away from the dust, water, stones and vibration that a tailshaft installation would be subject to. It would also allow you to continue to operate your analog speedometer and odometer while developing the digital ones. Another thought would be to get the transmission mounted component for a similar car that has an electronic speedometer. I'm going out on a limb here, but I believe they mount in the same place on the tailshaft, and output a number of pulses per driveshaft revolution. This solution (if at all 'do-able') would get you out of the mechanical construction part of the project entirely. It won't however allow you to run the existing speedometer and odometer in parallel. > > Shailendra > ssave@caen.engin.umich.edu > sumax!ole.uucp!ssave ------------------------------------------- Val Breault - vbreault@gmr.com The opinions expressed by the author do not necessarily reflect the position of the General Motors Research Laboratories or the General Motors Corporation.
berger@clio.sts.uiuc.edu (Mike Berger) (05/31/91)
ssave@ole.UUCP (Shailendra Save) writes: > I am trying to get a signal from the drive shaft of my car >using an inductive pickup. (To calculate and display speed) >Before I get under and get dirty, I wanted to know if anyone >has had any experience with a similar transducer? Can you >recommend one? The car being a big hunk of metal, and the >tolerances between the "magnet" and the pickup being of the >order of 0.2 in., will it work? *---- I'd be leery of putting a pickup right on the driveshaft. It doesn't take much to unbalance it at higher speeds, and the shimmy will probably be noticeable. -- Mike Berger Department of Statistics, University of Illinois AT&TNET 217-244-6067 Internet berger@atropa.stat.uiuc.edu
wilker@gauss.math.purdue.edu (Clarence Wilkerson) (05/31/91)
I used to have an add-on cruise control for a Plymouth. The pickup was activated by 2 small magnets taped and glued to the drive shaft, fairly near the transmission. The weight was small, and fairly balanced anyway. Clarence Wilkerson
ajf@maximo.enet.dec.com (Adam J Felson) (05/31/91)
In article <12974@mentor.cc.purdue.edu>, wilker@gauss.math.purdue.edu (Clarence Wilkerson) writes: >I used to have an add-on cruise control for a Plymouth. >The pickup was activated by 2 small magnets taped and glued >to the drive shaft, fairly near the transmission. The weight >was small, and fairly balanced anyway. > late model cars with a computer controlled engine sometimes have a sensor in the speedometer as an input to the computer. __ __a__d__a__m__
tomb@hplsla.HP.COM (Tom Bruhns) (05/31/91)
ssave@ole.UUCP (Shailendra Save) writes: > I am trying to get a signal from the drive shaft of my car >using an inductive pickup. (To calculate and display speed) >Before I get under and get dirty, I wanted to know if anyone >has had any experience with a similar transducer? Can you >recommend one? The car being a big hunk of metal, and the >tolerances between the "magnet" and the pickup being of the >order of 0.2 in., will it work? How about you pick up a replacement coil and magnet for an after- market automatic speed control? I once installed one from Sears that works fine to this day. The magnet was a tiny rare-earth thing that held to the shaft just by magnetism; it's never come loose. Never noticed any problem with imbalance; the magnet is very small compared with the mass of the shaft. The pickup was a coil of wire maybe an inch od, on a steel core as I recall, kinda like a relay coil, but not very many turns. If you need a sears part number, I might be able to find the 'manual'. Guess it may not be totally obvious: magnet goes on the shaft and coil is mounted to the car, nearly an inch gap as I recall.
jon_sree@world.std.com (Jon Sreekanth) (06/01/91)
In article <5170138@hplsla.HP.COM> tomb@hplsla.HP.COM (Tom Bruhns) writes: ssave@ole.UUCP (Shailendra Save) writes: > I am trying to get a signal from the drive shaft of my car >using an inductive pickup. (To calculate and display speed) >Before I get under and get dirty, I wanted to know if anyone >has had any experience with a similar transducer? Can you I've never worked with automobile electronics, so this might be totally off-the-wall, but ... isn't there enough leakage from the spark plugs, both as radiated and conducted interference for it to be picked up ? In other words, if you plug into the cigarette lighter, don't you see noise correlated with the spark plug firing on top of the 12V ? Can that be used ? Regards, / Jon Sreekanth Assabet Valley Microsystems Fax and PC products 346 Lincoln St #722, Marlboro, MA 01752 508-562-0722 jon_sree@world.std.com
ssave@ole.UUCP (Shailendra Save) (06/03/91)
From article <JON_SREE.91May31225851@world.std.com>, by jon_sree@world.std.com (Jon Sreekanth): > In article <5170138@hplsla.HP.COM> tomb@hplsla.HP.COM (Tom Bruhns) writes: > ssave@ole.UUCP (Shailendra Save) writes: > > > I am trying to get a signal from the drive shaft of my car > >using an inductive pickup. (To calculate and display speed) > lighter, don't you see noise correlated with the spark plug firing > on top of the 12V ? Can that be used ? > If I wanted a transducer for a tachometer, I would. I meant automobile speed when I said speed. Sorry about that. For the tach, I *am* using pulses from the primary of the coil. (A little cleaner and easier than the cigarette lighter) Good idea though. Shailendra ssave@caen.engin.umich.edu sumax!ole.uucp!ssave > > Jon Sreekanth > jon_sree@world.std.com
mike@delos.UUCP (Mike Newman) (06/03/91)
> ssave@ole.UUCP (Shailendra Save) writes: > > I am trying to get a signal from the drive shaft of my car > using an inductive pickup. (To calculate and display speed) > Before I get under and get dirty, I wanted to know if anyone > has had any experience with a similar transducer? Can you > recommend one? The car being a big hunk of metal, and the > tolerances between the "magnet" and the pickup being of the > order of 0.2 in., will it work? > > Any related ideas? There's a company called Zemco, Inc. that makes trip computers, cruise controls, etc. that use such a pickup, and it works very well! I've been using their products for years and, in fact, have both a trip computer (mainly for its speed function, which is far more accurate than my car's speedometer) and a cruise control connected to the same pickup coil. The magnets supplied in the kits are pretty strong, and being attached to the driveshaft doesn't seem to be a problem at all. The installation manual specifies 3/8" between the coil and magnets. Zemco also used to sell a speed transducer that was installed in-line with the speedometer cable. You may be able to find a similar device at a wrecking yard on a car similar to yours that has a cruise control, but the Zemco kit came with adapters to fit most appli- cations. Their address is: Zemco Group Inc. 7392 Count Circle Huntington Beach, CA 92647 Phone: (714) 842-6699 > Sometime ago, I asked the net about a weekend project to > make a tachometer for my car. I got numerous replies, for > which I am thankful. Hopefully I will soon have a complete > digital dash. I will post a summary for those interested. For those who don't want to build their own, a company called Cyberdyne makes some of the best looking digital guages I've seen... the speedometer and tachometer have both digital and "analog" displays. You may be able to use some of their sending units for your projects. Also, they make complete digital dash panels for some Camaros, Firebirds, and Corvettes. Cyberdyne products are sold by Summit Racing Equipment (look in just about any car enthusiast magazine for Summit ads). Good luck! Mike ============================================================================ ------- | |### | Mike Newman | Guns don't kill people... | o | All Around Computer Nut! | it's these little hard | U | racsys2!delos!mike@flight.hf.intel.com | things! ------- | -- the Flash ============================================================================
grahaf@otago.ac.nz (06/06/91)
In article <JON_SREE.91May31225851@world.std.com>, jon_sree@world.std.com (Jon Sreekanth) writes: > In article <5170138@hplsla.HP.COM> tomb@hplsla.HP.COM (Tom Bruhns) writes: > > > ssave@ole.UUCP (Shailendra Save) writes: > > > I am trying to get a signal from the drive shaft of my car > >using an inductive pickup. (To calculate and display speed) > >Before I get under and get dirty, I wanted to know if anyone > >has had any experience with a similar transducer? Can you > > > I've never worked with automobile electronics, so this might be > totally off-the-wall, but ... isn't there enough leakage from the > spark plugs, both as radiated and conducted interference for it > to be picked up ? In other words, if you plug into the cigarette > lighter, don't you see noise correlated with the spark plug firing > on top of the 12V ? Can that be used ? > Ummm. Sort of. But there are two problems. One isn't so much a problem as an easier way. If you look at the voltage across the ignition points in the distributor then you get a nice low voltage, relatively clean signal, BUT it is only related to engine speed not car speed. The gearbox is in the way. If you have an automatic then there is some slippage between the transmition and the engine. If the car is in neutral then there is a signal with no speed at all :). I remember in the late seventies/early eightyies when trip computers first came out, many of the kits used an input from the drive-shaft. This was done with magnets and a Hall-effect device I think. There were four small magnets spaced equally around the shaft and wired in place, the magnets are small enough to not effect the shaft balance. I have no idea of the availability of the kits now but there may be someone with an old one you can canabilise. good luck, Graham.
jon_sree@world.std.com (Jon Sreekanth) (06/07/91)
In article <1991Jun6.151435.484@otago.ac.nz> grahaf@otago.ac.nz writes: > totally off-the-wall, but ... isn't there enough leakage from the > spark plugs, both as radiated and conducted interference for it > to be picked up ? In other words, if you plug into the cigarette > lighter, don't you see noise correlated with the spark plug firing > on top of the 12V ? Can that be used ? > Ummm. Sort of. But there are two problems. One isn't so much a problem as an easier way. If you look at the voltage across the ignition points in the distributor then you get a nice low voltage, relatively clean signal, BUT it is only related to engine speed not car speed. The gearbox is in the way. If you have an automatic then there is some slippage between the transmition and the Well, I actually got to thinking about this in context of a 'transportable trip computer'; something you could use on rental cars, for example. Then rather than messing around under the hood, you could plug the sensor into a (still messy but more accessible) cigarette lighter. Of course, being a tacho indication, not a speedometer indication, is a fatal flaw. Regards, / Jon Sreekanth Assabet Valley Microsystems Fax and PC products 346 Lincoln St #722, Marlboro, MA 01752 508-562-0722 jon_sree@world.std.com
bender@oobleck.Eng.Sun.COM (memory fault - core dumped) (06/07/91)
In article <JON_SREE.91Jun6225924@world.std.com> jon_sree@world.std.com (Jon Sreekanth) writes: ->In article <1991Jun6.151435.484@otago.ac.nz> grahaf@otago.ac.nz writes: -> -> > totally off-the-wall, but ... isn't there enough leakage from the -> > spark plugs, both as radiated and conducted interference for it -> > to be picked up ? In other words, if you plug into the cigarette -> > lighter, don't you see noise correlated with the spark plug firing -> > on top of the 12V ? Can that be used ? -> > -> ->Well, I actually got to thinking about this in context of a 'transportable ->trip computer'; something you could use on rental cars, for example. ->Then rather than messing around under the hood, you could plug the ->sensor into a (still messy but more accessible) cigarette lighter. Since most (all?) late-model cars have engine computers, and I belive most of the computers have a service/diagnostic port somewhere on the car, is it possible that you could periodically interrogate the engine computer for the various parameters that you're interested in? There's probably not a standard way to do this yet, but I have heard of GM (and other automobile manufacturers) proposing a vehicle network where most of the electronics on the vehicle would talk to one another with a standard signalling protocol. mike -- ------------------------------------------------------------------------ 1985 Honda Shadow VT1100 | DOD #000007 1989 Honda NX-650 | AMA #511250