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Three Generations
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Picture of PHPaul
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I bought a digital speedometer to put on an ATV. It uses a rim-mounted magnet to trigger a sensor. The gauge can be calibrated to a range of wheel sizes and magnet counts, but the instructions are VERY basic.

What I have to work with is "For example, if the tire circumference is 81.375 inches and there are 6 magnets, the setting is F08.0"

F is the variable to calibrate the speedo.

What I need is to convert that into a formula where I can plug in the tire circumference and magnet count and determine the proper setting.

Tire circumference is 66" and I plan to use 2 magnets.

My thinking: With 6 magnets we have 6 pulses per revolution and each revolution covers 81.375 inches, or 13.56 inches per pulse and the proper setting to convert that to KPH is 8.

With a 66 inch circumference and two magnets, I get 33 inches per pulse.

Assuming the 8 is a multiplier (with no particular evidence to support that assumption), I get an input of 108.5

108.5/33 is 3.29 rounded off. My first thought is to enter that as the F parameter.

The only other instruction is "the higher the number the slower the actual readout is"

Does any of that make any sense or do I have a bad case of cranio-rectal inversion?
 
Posts: 9984 | Location: Downeast Maine | Registered: March 10, 2010Reply With QuoteReport This Post
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Need more info. Suggest you post the name and model number of the speedometer.
 
Posts: 2189 | Location: North Carolina | Registered: August 16, 2003Reply With QuoteReport This Post
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Posts: 9984 | Location: Downeast Maine | Registered: March 10, 2010Reply With QuoteReport This Post
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Posts: 15501 | Location: Northern Virginia | Registered: November 08, 2008Reply With QuoteReport This Post
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Probably ought to ask Ambuker.
 
Posts: 268 | Registered: January 20, 2011Reply With QuoteReport This Post
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Would this cheat work? Do the install then use gps or another vehicle to travel at a selected speed and keep changing the variable number until you match.


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Posts: 3082 | Location: Kenton, Ohio | Registered: December 27, 2008Reply With QuoteReport This Post
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Google chinese digital speedometer and you will find youtube videos of what appear to be the same speedo you bought. The few I looked seem to be about the wiring, but maybe you'll get lucky.



There are more videos in the right margin.

Ambucker is a trademark name of Shenzhen Qiyu Auto Parts Co., Ltd. No luck in finding a website or manual.
 
Posts: 2189 | Location: North Carolina | Registered: August 16, 2003Reply With QuoteReport This Post
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quote:
Originally posted by tsmccull:
Probably ought to ask Ambuker.


I did. Their reply was entirely useless beyond the example I posted.
 
Posts: 9984 | Location: Downeast Maine | Registered: March 10, 2010Reply With QuoteReport This Post
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quote:
Originally posted by mikeyspizza:
Google chinese digital speedometer and you will find youtube videos of what appear to be the same speedo you bought. The few I looked seem to be about the wiring, but maybe you'll get lucky.



I've been surfing YouTube for hours. Everyone is asking the same question, no one seems to have an answer.
 
Posts: 9984 | Location: Downeast Maine | Registered: March 10, 2010Reply With QuoteReport This Post
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There is a reddragonfly or red dragonfly speedo that appears to be the same one.

There are 94 Q&As on amazon for it so maybe an answer is there.

https://www.amazon.com/dp/B00W...leproductsreviews-20
 
Posts: 2189 | Location: North Carolina | Registered: August 16, 2003Reply With QuoteReport This Post
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I think the example is bad and can not come up with what F08.0 actually converts to for the given parameters.

Since the speedo is in KPH - using mm your 66" wheel = 1676.4 mm - 2 sensors per revolution means your wheel travels 838.2 mm (33") per sensor.

I say for two sensors start with 838 and fine adjusts from there.

"the higher the number the slower the actual readout is" I think this means the less sensors the slower the response is - one sensor=one pulse adjustment per revolution, 8 sensors=8 pulse adjustment per revolution. It can calculate for each sensor input, probably more important when accel/decel rather than steady state.

And I found this in youtube, some one just did the mm circumference/# sensors and adjusted from there using GPS (I guess you could have a car or motorcycle be the check if no GPS).



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Posts: 2027 | Location: Idaho | Registered: January 26, 2014Reply With QuoteReport This Post
Three Generations
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Yup, I've come to the same conclusion: Pace it with something and tweak it from there.

I currently have one magnet on the rim and giving it a healthy spin DOES result in a reading, but there's a lot of lag. More magnets/more readings/faster response makes sense. Just need to pick up some more magnets.
 
Posts: 9984 | Location: Downeast Maine | Registered: March 10, 2010Reply With QuoteReport This Post
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Try F=20 for two magnets then spin the wheel.
 
Posts: 1060 | Location: County 18, OH | Registered: April 11, 2007Reply With QuoteReport This Post
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