This is the ne555 that i purchased.

Actually, to be picky, it's a pulse generator module with adjustable frequency and duty cycle, albeit one including a NE555 IC . Let us know if it does the trick.

 

This is the ne555 that i purchased. I am hoping it can get the job done

YES it should be ok on the 50Hz 1Khz setting, from reading your posts if your speedo needs a 5V square wave, just power the 555 pcb with 5V, and input it directly, set your Frequency to 120 to 140Hz.

 

The reason for the electro-magnet is so I don't have to hook anything up to the vehicle. In the off chance I did something wrong - I would be isolated by the magnet.

Yes, that board will do what you want. If you go with the magnet you'll need a driver transistor because the 555 can not drive the magnet alone. You'll burn it out quick. But I suppose if you ground your 555 to the car chassis ground then the pulses will act like the pulse train from the sensor.

 

Great info guys. I will surely update you all on the outcome. Seems like all I am missing is a voltage reducer. I have a motorcycle charger that outputs 6v but i need 5v and under. Any idea where I can find a voltage reducer locally? Radio shack is not a option for me. They were all closed down.

 

Successful results! I am using a ac to dc usb wall adapter. I cut the micro usb section off. I stripped the wires and am using the red and black wires. Which provide 5v. I have the usb postive and negative wired into the ne555. I had to also connect a ground from my motorcycle to the ne555 ground terminal input. Adjusted the frequency and duty cycle and i have it set at 160mph. Its going through 10 miles at 1-2 minutes. So not bad at all. Thank you all for your help

 

160 MPH. In one hour your odometer will advance 160 miles.

In 10 hours, 1600 miles.

In 20 hours, 3200 miles

In 25 hours, 4000 miles.

So it should take you 25 hours at that speed (rate) to advance your odometer 4,000 miles.

So, tomorrow, in a half hour from now you'll be just about at your goal.

 

Awesome! Makes sense to me. So I will leave it plugged in overnight and have a look tomorrow.

 

I would suggest if you want to achieve a specific target mileage, as you approach your distance you slow down the rate at which you are moving forward. In other words, slow down an hour before you reach your goal and recalculate how much further you have to go. Then set a speed that will help you get even closer to it. THEN, when you're nearly there, shut off your circuit and start advancing the reading mechanically. On your vehicle, if it takes 2 pulses per revolution of the driveshaft (like my truck) and 4.1 revolutions of the driveshaft per rotation of the tire, and your tire size is known then you can figure out how many more manual inputs you need to achieve your target.

Here's how you calculate the tire rotation: A 255/75R16 (such as my truck is) you multiply the 255 by 0.75, then by 2. Then you convert that (metric) number into American Standard Engineering (ASE) by multiplying it by 25.4. Then you add 16 and you get the overall height of the tire.

255 is the tire width, 75 is the percentage of width to sidewall height and the 16 is the rim size. So:

255 x 0.75 x 2 ÷ 25.4 + 16 = 31.06 inches tall.

NEXT, calculate the circumference of the tire. 31.06 x 3.1416 (the value of pi) and you get 97.575 inches around the outside of the tire. That means the tire rolls forward 97.6 inches forward for every revolution. In the case of my truck, that's 97.6 x 4.1 x 2 (pulses per driveshaft rotation) = 800 pulses (for one tire revolution). There are 5280 feet in one mile. That's 63,360 inches per mile.

[CORRECTION] ONE tire revolution results in 8.2 pulses, not 800. So the rest of my numbers are way off. Sorry. The rest of what I stated will be deleted and corrected as well. If you've already looked at my numbers, know that they were incorrect to a great degree.

63360 ÷ 97.6 = 649.2 tire revolutions per mile.

8.2 pulses per revolution times 649.2 tire revolutions equals 5,323 pulses per mile. Running at 50 Hz would take 10.6 seconds to advance one mile. From here it should be easy to get REAL close to your target. Once you're VERY close you can switch to manual inputs using just a switch. If switch debounce is your worry, don't. With 5,000 pulses per mile, switch bounce might get you closer quicker. As for over-run - it shouldn't be very much, maybe on the order of a tenth of a mile. So I wouldn't worry about switch bounce.

 

Late Entry: In post #28 I made an error. A rather HUGE error. If you've already read that post and have started calculations based off my bad numbers - STOP. Re-read the post as I have corrected those numbers.

 

Sorry to revive an old thread. I have a yamaha apex snowmobile that I replaced the odometer on. I somehow got a short in the original. The original odometer read 23,848 miles. I replaced it with a new one, and have 3,690 miles on it this year. I want my new odometer to read the true mileage. Is there someone i can send the odometer to, to have it advanced to read the correct mileage. Reading through this thread, this stuff is way over my head. I have seen videos on youtube, where they took the chip that stores the odometer reading out of the odometer, and hooked it to a computer to advance the reading. This looks way advanced for anything i can do.

 

Speedometer calibration shops around your area are equipped to flash the new odometer to the old one. You'll need to call around and find someone who does that sort of thing. If you can't find someone then try calling your Department of Motor Vehicles and see if they know of someone who modifies speedo's.