3,789 MPH!

Brian Diehl · January 04, 2011, 05:37:37 PM

Well, my old speedometer started acting up on my last trip out. The odometer display would just start showing random digits and then after a while would go back to showing the correct mileage. This continued to get worse and worse over the past 5000 miles. It is so bad now that the display tends to blink the incorrect mileage more than it shows the correct mileage. The strange thing is the is only a display issue. When it displays the mileage correctly is correctly accounts for the mileage traveled since it last displayed correctly. I spoke with VDO tech support and they confirmed unless I wanted to tear apart the speedometer there was nothing I could do. We ruled out voltage issues, signal issues, etc. and came to the conclusion the issue must be in the solder joints between the display and the internal circuit board.

So, I decided to get a new speedometer before my current one completely quite. Of course, they wanted $45 to set the odometer to my current reading. Me, being the cheap skate I am decided I would live with the 0.0 miles on the new odometer. However, as I got to thinking about it I decided I could probably just put on those miles manually. I have a 24v power supply and a spare pulse signal pick up. So, I rigged up the below setup to add miles on. The needle only shows 90 mph. However, the miles are rolling by on the odometer at the rate of 3,789 MPH! It will still take a long time to get to my target mileage, but it was fun seeing my idea pan out and work!

Len Silva · January 04, 2011, 05:44:04 PM

I think you can just use a transformer and a diode to generate 60 pulses per second from the house power. Just have to make sure the voltage is right for the speedometer.

Brian Diehl · January 04, 2011, 05:47:51 PM

Quote from: Len Silva on January 04, 2011, 05:44:04 PM
I think you can just use a transformer and a diode to generate 60 pulses per second from the house power. Just have to make sure the voltage is right for the speedometer.

Good idea, I never thought of that!

However, the speedo's minimum pulse rate is 500/mile.
So, at 60 pulses a second from house power I would be "traveling" at 500/60=8.3 miles per second. This = 498 mph.

fe2_o3 · January 04, 2011, 06:20:16 PM

Red Green would be proud.

Brian Diehl · January 04, 2011, 06:38:30 PM

Quote from: fe2_o3 on January 04, 2011, 06:20:16 PM
Red Green would be proud.

Just missing a little duct tape!

Chopper Scott · January 04, 2011, 06:49:38 PM

Keep your stick on the ice....

fe2_o3 · January 04, 2011, 07:04:22 PM

If the women don't find you handsome, they should at least find you handy.

Chopper Scott · January 04, 2011, 07:17:31 PM

Wouldn't be complete without this worn out link!! Red Green Show - Old TTC Bus

gumpy · January 05, 2011, 04:31:42 AM

I did a similar trick a couple years ago when my pickup wire broke in WY. I wanted to correct the mileage when I got home and fixed it, so I chucked a spade bit
into a $5 cheapo drill motor. Ran it over night. Pretty much ruined the drill motor, but got the mileage where it should be. Just makes record keeping a bit easier.

I like the hole saw teeth idea. Would not have expected the hall effect sensor to pick up each tooth.

RickB · January 05, 2011, 04:49:02 AM

So Brian are you getting younger as you spin it? I knew eventually the fountain of youth would be found by a busnut!
I actually use the garmin as my speedometer more than my actual one.
RB

Brian Diehl · January 05, 2011, 06:04:48 AM

No, I'm not getting any younger ... but, maybe getting older more rapidly!

I've never seen the Red Green show clip linked in. Thanks for sharing it!

Craig, the hole saw needs to be really close to the sensor to work, but it does work fantastic once it is close enough!