Speedometer for fourwheeler.

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ckbrown
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Speedometer for fourwheeler.

Post by ckbrown » Mon May 08, 2006 9:58 am

Greetings to all

I have a project that I am working on for my boss. He has a Polaris farm fourwheeler with dumper on the back. We added a spray tank to the dumper and spray heads to the support hardware to be able to apply liquid fertilizer to his pasture land.

He say we need a speed indicator to be able to to keep the application rate constant. I remember a article where someone in Nuts and Volts added a speedometer to his lawn tractor by counting the teeth of the main drive gear in the chain drive. I cannot do this as the Polaris uses a driveshaft and differential to the axles. I measured the travel of a wheel in 1 revolution and got 76.5 inches. I also counted the turns of the drive shaft by tying a string to one of the arms of the yoke of a u-joint. I got 3.5 turns per tire revolution. After the math (5280/(12/(76.5/3.5)))/60 gives 48.3145 revolutions per minute at one (1) mile per hour. I need a little help with the display unit. I need the unit to be adjustable in the divisior, in a panel mount, as watertight as possible, 1 or 2 decimal places.

Thanks in advance for all your help.

Curtis

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Chris Smith
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Post by Chris Smith » Mon May 08, 2006 10:13 am

I would purchase a cheap Tachometer and fit it to a wheel using a reflective mark on the rim.

Then all you have to do is work out the correct speed and mark the dial out in rpms.

If the tach doesn’t have good resolution at slow speeds, use the drive shaft.

You can even repaint the tach face to read the Apx. Set point speeds, the sweet spot, or even different colors for different gears.

Newz2000
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Post by Newz2000 » Mon May 08, 2006 10:45 am

I used to work for a company that manufactured computer read sensors and meters that were fit to combines and other farm equipment. Instead of relying on a speedometer they used a "ground speed" sensor. I don't know what that is, but it makes sense... if your wheels slip your speedo will show the wrong rate, but the ground speed sensors don't suffer this problem.

Maybe this is more critical when measuring flow and grain moisture than for applying fertalizer.

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Chris Smith
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Post by Chris Smith » Mon May 08, 2006 10:58 am

That’s a interesting concept.

Perhaps you can modify an optical mouse to measure not only motion, but speed and direction into a meter, with a better lens and some hardware?

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Sambuchi
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Post by Sambuchi » Mon May 08, 2006 10:59 am

Hello ckbrown

Well heres a slightly biased opinion if you are thinking of using a mico (for the math calculations and inputs) and a display unit(for speed or total distance).

I would use an MSP430f449 processor with a softbaugh display. Here a picture of a demo board from softbaugh.

http://www.softbaugh.com/Show.cfm?strPartNo=ES449

You could purchase the above board or make one your self for cheap...

The MSP430 is free..discrete parts may run 2.00 and the LCD 15.00. Board manfacture 20.00.

If you want more detail info on how to build one let me know..



Another way to count the wheel posistion.... build your own shaft encoder. Here an example on a smaller scale.

http://www.sambuchi.net/Projects/Sensor ... r_home.htm

Good luck

Robert Reed
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Post by Robert Reed » Mon May 08, 2006 11:03 am

Since the LM2917 post has been receiving a lot of attention here, I will the suggest the cheap,quick and simple way. Use what ever is conveniant and where ever it is conveniant to establish a pickup point (e.g.-A magnet firmly attached to a rotating member along with a pickup coil) Feed this output into an LM 2917 and drive a digital volt meter with it. You could even use an analog meter. Calibration in either case would be very simple by just scaling your output to match the speed (pulses per second) in MPH (volt) or even furlongs per fortnight :grin: if so desired. I built up a similar project a few years back for a Jet Ski tachometer, using an analog meter. This unit performed very well with about 1% accurracy. Since it doesn't sound like you need extreme accurracy, simple would be better. Install in a water proof box with a sealed plastic plexiglass cover and you should be in bussiness.

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Externet
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Post by Externet » Mon May 08, 2006 11:22 am

Or, install a speedometer from the bicycle gadgets store with the sensor on a shaft. It will log trips too. :smile:
Miguel

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Sambuchi
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Post by Sambuchi » Mon May 08, 2006 11:39 am

well.. looks like you have lots of options... i just found what I wanted to post the first time..

heres the main page to use the msp430 with a Tachometer.
http://focus.ti.com/docs/apps/catalog/r ... me=slaa259

this page will give you the code and hardware/ application note for a Tachometer ... they used the Tachometer to PWM a motor but the (PWM) code can be deleted. they also provided code for the display...

Good luck

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haklesup
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Post by haklesup » Mon May 08, 2006 2:36 pm

Just about any GPS reciever will give you speed without any additional connections but it can be somewhat innacurate at times if the update rate is slow and can be confused when you bang a U turn. It will have tha added benefit of helping him verify the mixture is spread evenly. post processing of the trip log can further yeild coverage data.

For simplicty and cost, the bike speedometer idea from Extranet can't be beat. Make sure you get a model that you can program the wheel diameter in the range of your tractor or put a trailing bike wheel behind the tractor or aside the hopper (chopped from the front of an old kids bike). These are good down to a few MPH, any slower you can use multiple sense magnets on the wheel rim and divide by that number to get the real speed.

If the exact speed is not important but maintaining a certain rate, then a simple DC generator connected to the wheel will make a voltage you can feed to an analog meter movement marked with go faster, go slower and just right (in the middle). A potentiameter and/or resistor divider is all you need to calibrate for a particular rate. A diode may or may not be needed depending on the generator you select (any DC motor spun by the wheel to make electricity as opposed to the other way around)

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dacflyer
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Post by dacflyer » Mon May 08, 2006 5:06 pm

heres a thought,,,use a simple GPS....
they measure speed time miles etc,,,

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Chris Smith
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Post by Chris Smith » Mon May 08, 2006 6:12 pm

Do any GPSs actually measure down to one MPH, accurately?

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jollyrgr
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Post by jollyrgr » Tue May 09, 2006 1:57 am

Externet has the right idea. Get a bicycle "computer". These are speedometers with many functions. Some are even "wireless" which means you can mount the sensor on a wheel and mount the display some two feet away. Depending on how fancy you want to get you can pay anywhere from $20 to $100 for one. Even the cheap end ones have an odometer and speedometer functions. Just be sure the one you buy can be programmed for the diameter of the wheel of the four wheeler.
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dyarker
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Post by dyarker » Tue May 09, 2006 2:25 am

I would suggest against optical sensors on farm equipment. Dust or mud!
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Engineer1138
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Post by Engineer1138 » Tue May 09, 2006 10:50 am

The bike computer is a good idea if you can program it with such a small wheel diameter, but doesn't Polaris or one of the other ATV manufacturers already offer an odometer/speedometer that you could attach?

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jollyrgr
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Other People's Experiences

Post by jollyrgr » Tue May 09, 2006 3:53 pm

See these for ideas along this line:
http://www.utahatvtrails.com/ATVAccessories.htm

Custom made for ATV/Dirt bikes:
http://www.trailtech.net/atv_computer_kits_1.htm

Here is a 4WD Polaris installation:
http://www.trailtech.net/polaris4wd.htm
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