Maintenance reminders


Senior Member
Has anyone done anything with automating maintenance reminders for the car? I'd love to have an icon on my touch screen or a TTS or something come up when scheduled maintenance is due. I know it is easy to put a timer based reminder but what about somehow tapping into the odometer or some kind of sensor on the driveshaft or something? Something that can determine mileage and send that info wirelessly to a pc or M1 or something? Anyone ever try this? I keep missing oil changes especially in the wifes car because she never tells me the mileage.
They sell OBD-II interfaces which would let you pull all that data from car computer. But you need to somehow interface this, using wireless, to your house, which means there has to be some sort of really smart controller involved, such as a PC or PDA.

The only other way I can think of is by monitoring the car using GPS, and do the math that way.
This is a great post! I have an idea just off the top of my head that I might look into.

You can place a magnetic sensor on the drive shaft and "count" the number of turns with something like a binary counter. When the "count" equals the number of miles desired you could then send an X-10 signal via a palm pad hack (or DS10a). The counter would then be reset.

Some of these design concepts were done in my first method of my X-10 Car Monitor. If you refer to THIS schematic from that How-To you will see that the binary counter counts pulses from the 555 output chip, then when the count equalls a half hour (equivalent counts), the output sends a relay closure to the palm pad remote (sending an X-10 signal), then resets the counter.

Something like this can be used except have the magnetic contact from the drive shaft send "counts" to the binary counter. Some circuitry might be needed to clean up that pulse (Schmitt trigger for instance). One would also have to calculate drive shaft rotation verses miles and select the output counter output accordingly (you can always cascade counters to get higher counts).

One big problem would be making sure power was always applied to the circuit so some sort of battery backup would need to be employed. Another would be to make sure the car was in range of an X-10 receiver when it reached that count! (Could always just send a pulse so many seconds till it was manually reset).

Well, I only gave this about two minutes of thought, so maybe this could be a catalyst to start some interesting discussions!
My car know-how isn't that great, but if you monitor the driveshaft, wouldn't that return bad results because of the gearing etc?
electron said:
My car know-how isn't that great, but if you monitor the driveshaft, wouldn't that return bad results because of the gearing etc?
Hmmm, not sure. Might have to monitor some other way I guess. Perhaps tire rotation!

This is a good question. The ratio between tire rotation and drive shaft should be constant though as the transmission selects how the "engine" turns (RPM's) in relation the the shaft, but the shaft ratio to the tires should always be the same.

Of course, I haven't had my full quota of coffee this morning.
There are two challenges. First, how to glue the magnet to the shaft so that it does not blow out flying (very dangerous). ANd second, how to make sure that you dont affect the balance of the shaft. You will have to stick two magnets at 180 degrees, or three at 120. Not an easy task.
Having done this in the past (long ago), you put two magnets (same weight and type) on opposing sides of the driveshaft. Use reference to the UJoint to determine equidistants. Double stick tape on the backside to keep the magnets from slipping sideways (not to keep them attached to the shaft!). Then, use stainless wire to wrap over the magnets to affix to them to the shaft. There will be LOTS of force on these magnets so do a good job and keep things weight balanced (including number of turns in the tie wrap). The shape of the magnet (square with idents for the wire) makes a difference (don't use round).

The magnets get mounted as close to the U Joint towards the transmission since that is the side that has the least lateral movement with suspension travel. You also mount the hall effect transducer on a horizontal plane with the driveshaft to account for up / down of the suspension. Figure in the suspension travel 1/2 way (vehicle weighted down) when affixing the transducer location. For most transducers, mount with a 1/8 inch air gap.

You use software to calibrate the number of pulses = 1 mile with a transform formula. Transmission ratios are before the driveshaft so no affect on driveshaft speed / road speed calculations. Air pressure in tires has more affect, but only a smaller percentage. Measure the road surface to the axle midpoint which is the radius of the circle and then calculate the circumferance of the circle divided by rear axle gear ratio divided by two (number of magnets) should get you close to the transform number.

Another more modern way is that most all vehicles use a "speed sensor" which is mounted on the transmission. Some are mechanical reed switches that click off output shaft rotation (driveshaft). Some are hall effect sensors which monitor a pulse wheel in the transmission. These can be tapped into electrically for their signal return. But, keep in mind that these circuits are usually monitored for health by the transmission controller and can throw a diagnostic code and light if they don't see the voltage that the controller expects under the circumstances that it is being monitored. So, use a optical or other semiconductor sniff of the voltage state to not induced any resistance or voltage.

"OBD2" is a better idea, unfortunately "OBD2" specification does not include odometer. Each OEM stores, presents, calculates Odometer in a unique way. There are also multple storage places in multiple control modules for the odometer. So, you need a scan tool that goes beyond OBD2 and into "Enhanced Data" which is OEM specific.

And as a tease, a solution for this problem is in the works :)
WOW, very cool David. I knew someone would have some great input for this idea.

So, what kinds of measurements did you take overall? What circuitry did you use?

Does your future solution include a notification to an HA computer?
If it is a front wheel drive, the axle rotation will be equal to the tire rotations. If it is a rear wheel drive vehicle with a differential, then the drive shaft speed will be higher and the final wheel speed will be determined by the gear ratio of the differential. If it has "live" axles between the differential and the outer hubs, then of course this would be the same scenario as the front wheel drive vehicles.
As far as attaching small magnets, the very early versions of an aftermarket cruise control system required you to glue (like a contact cement) the magnets on the drive shaft then wrapping them with a fiberglass shipping tape. Later versions allowed the use of a cable tie to help secure them.
For me I just set up an estimate based on the average use in a given time frame and have an event that pops up. Most peoples average mileage varies very little. It at least reminds me to go look at the service sticker on the wifes car.
Not real hi-tech, but it works.
Actually the OEMs are doing more than just mileage. Usage style is now factored in for in car oil change reminders. Adaptive shift factor is one of the parameters used. This is how a newer electronic shifted vehicle (most are now) adapts to the driving style. A mild driver gets earlier, slower shifts (very smooth) while a more agressive driving style gets higher rpm and crisper shifts (more performance plus saves the transmission life). This same factor is used to condition when the maintenance light comes on.

I used the magnet deal for one of those early cruise control systems plus a modified speedometer that I used in a Datsun 240/ 280Z that had a 350 chevy V8 motor in it. I subsequently converted that car to my own digital fuel injection system (which I still own years later :) )
BraveSirRobbin said:
Wow, another great post! What circuit do you use to count the pulses Gemini!
Uh... I don't. The reminder is just based on the "average" use of the vehicles....which for most folks varies very slightly from month to month.
Gemini said:
BraveSirRobbin said:
Wow, another great post! What circuit do you use to count the pulses Gemini!
Uh... I don't. The reminder is just based on the "average" use of the vehicles....which for most folks varies very slightly from month to month.
Ah, I misread that last part of your earlier post! Makes sense now!