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View Full Version : How do taxicabs keep track of milage?



Brian Carpenter
02-18-2007, 12:47 AM
I dont know much about the OBD2 but is it possible to get a pulse from the OBD2 for every mile traveled?

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Post Edited (Brian Carpenter) : 2/17/2007 10:00:39 PM GMT

Brian Carpenter
02-18-2007, 12:56 AM
i am trying to make a device that will track milage. kinda like a taxicab. I have 20 different locations that i bill milage to each week. I was looking to make a device that would have twenty buttons, one for each loacation. When i press a button for a location, it will log the odometer reading with the associated number pressed. When a new location is press it will associate the new odometer reading with the old location as an end and the new location as a beginning.

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Brian Carpenter
02-18-2007, 10:39 PM
any guesses

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Forrest
02-18-2007, 10:46 PM
I've seen GPS systems used for driving directions and also to track the driving route, time, etc.

Brian Carpenter
02-19-2007, 04:27 AM
Is there any way to monitor miles traveled from the vehicle without GPS?

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Franklin
02-19-2007, 05:07 AM
How about the odometer? (on the dash)

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- Stephen

Franklin
02-19-2007, 05:25 AM
The ODB-II standard apparently puts out vehicle speed in KPH. you could use this and time to compute distance.

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- Stephen

Brian Carpenter
02-19-2007, 05:51 AM
Franklin,
This is also what i was thinking. Is there access to the odometer through the OBD-II?

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RGuyser
02-19-2007, 06:42 AM
i believe i have been told the cabs use an odometer or tachometer hooked to the engine at some point.. possibly the alternator.. but then, that would not account for the gearbox..... so, it seems a hall sensor and magnet on the tire hub may be rational?

and instead of 20 buttons, consider an LCD and 2 or 4 buttons!

a 20 button device is a nightmare!

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LSB
02-20-2007, 03:54 AM
The EPA mandates standard sensors for emission equipment monitoring, beyond that the manufacturer may/ may not put sensors on or for about anything they choose (and output accordingly). I'd start with standardized and required sensors (info from EPA or high school auto shop perhaps) then contact specific vehicle manufacturers for additional information. Also, online resources like www.obdii.com may have forums and, undoubtedly, more complete information than you’re likely to get here. That said, I think there would be interest here in how to interface to, or extract the info from the OBDII data stream. Here in Oregon some counties are experimenting with this technology to figure road tax--I know what you're inquiring into is possible.
Aside, I saw some time ago reasonably priced chips that read this data stream to an ASCII serial output… specific to vehicle manufacturer.

PJ Allen
02-21-2007, 09:27 AM
Here's an "aside" regarding car odometers --

Honda's had some fuss & bother with odometers thought to be incrementing too quickly on Accords. But what got my interest was that accuracy can "acceptably" be off by 4%.

steve_b
02-22-2007, 01:40 AM
On my Jeep TJ I had upgraded from stock 29" tires to 31" tires.
I borrowed a GPS and found that my speedo was dead-on for the 31" tires.
So basically my jeep had excessive mileage on it than if the speedo gears were set properly.
There's always some slop, but it still adds up and reduces the resale value of my vehicle.....anyhow, have talked to other Jeep owners (different models) and some have found similar things!

Just an FYI!

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

John R.
02-22-2007, 01:53 AM
steve_b said...
On my Jeep TJ I had upgraded from stock 29" tires to 31" tires.
I borrowed a GPS and found that my speedo was dead-on for the 31" tires.
So basically my jeep had excessive mileage on it than if the speedo gears were set properly.
There's always some slop, but it still adds up and reduces the resale value of my vehicle.....anyhow, have talked to other Jeep owners (different models) and some have found similar things!

Just an FYI!


There is a tendancy/preference to "bias" the speedometer so that it reads "low" with "standard" sized tires. This is so that you are not likely to be able to say "well my speedometer said 55".

This may, or may not (especially in the days of digital dashboards) be directly related to the odometer.

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John R.
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