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Electronic Dead Reckoning Distance Calculator

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jan 11, 2010 7:25 pm Post subject: Electronic Dead Reckoning Distance Calculator

At 09:47 AM 1/11/2010, you wrote:




Bob,

Thanks for your comments.  I am really proud of this project, but did 

not expect many replies because GPS has made dead reckoning 

obsolete.  You and another friend suggested using a PIC 

micro-controller.  Unfortunately I know very little about them.  I 

understand that a programmer is required.  It was fun learning how to 

program the CD74HC4059 counter-divider.  Learning how to program a 

PIC micro-controller should be fun too.

   There's a ton of pic development systems out there

   for under $100, dozens for under $50. You might

   think about subscribing to Nuts and Volts magazine



http://www.nutsvolts.com/



   Their advertisers include a number of hobbyist PIC

   systems to get started with. The one we use here is

   only $29 and comes with an exceedingly capable editor,

   assembler package. I think it's the PicKit II. You can

   go the assembler route (I think there's only 35 instructions

   to learn how to use) or the Tiny Basic round offered in

   the Basic Stamp series systems . . . and others.



http://www.parallax.com/



http://www.parallax.com/Resources/GettingStarted/tabid/270/Default.aspx



  There are programmers listed on eBay from $15 to over $200.  Does 

anyone have a suggestion on which one to buy?



   This one is $100 but probably your best bet to get

   up and running quickly in Tiny Basic or Assembler



http://tinyurl.com/yfxgka4



   See also:



http://www.mstracey.btinternet.co.uk/pictutorial/picmain.htm



http://tutor.al-williams.com/pic-intro.html



http://www.hobbyprojects.com/microcontroller_tutorials.html

   I want to build a capacitance to voltage converter for a fuel 

gauge like this:http://www.rstengineering.com/kitplanes/KP0007/KPsch.jpg

Can a PIC micro-controller replace much of that circuit?



    Oh my, yes. I've been halted on a program to do just that.

    The program manager ran out of money. It might come back

    in the spring . . .



    The philosophy I'm using alternately charges the

    tank capacitance through a large value resistor

    and discharges it with a transistor. The time it takes

    to charge the capacitor from zero to some reference

    value is measured by the uP. Every other charge/discharge

    cycle, a 100 pf reference capacitor is switched across the

    tank line and the time to charge total capacitances is

    measured.



    By having a reference capacitor, calculation of tank

    + wiring capacitance is a simple ratio that wipes out

    errors in charging current or comparator trip voltages.



    System accuracy is dependent only on stability of

    the reference capacitor and timing accuracy of the uP

    (crystal controlled).



    I can't offer you anything more than that right

    now but I  can assure you it's well within the capability of

    the PICs to do the timing, operating the capacitor

    switch and calculating a PWM output value that

    represents % of tank contents. What's more, the

    total parts count is VERY low.



    Bob . . .

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pmather

Joined: 17 Sep 2009
Posts: 33

Posted: Tue Jan 12, 2010 1:04 am Post subject: Electronic Dead Reckoning Distance Calculator

Unless you need very fast program response look at www.picaxe.co.uk. The 

chips are available worldwide.



These are pic chips pre-programmed with a basic interpreter and need nothing 

more than two resistors and a serial cable to connect to a PC and program. 

The software for the PC is completely free.



The support on the forum www.picaxeforum.co.uk is fantastic and the chips 

have i2c, pwm, etc. capability all available in the interpreter



I can and do use PICs directly programmed in C /assembler using various 

programmers but for quick prototyping and many applications the picaxe can 

not be bettered



best regards



Peter



From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

To: <aeroelectric-list(at)matronics.com>

Sent: Tuesday, January 12, 2010 3:22 AM

Subject: Re: Re: Electronic Dead Reckoning Distance 

Calculator

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 At 09:47 AM 1/11/2010, you wrote:

 

 <fran4sew(at)banyanol.com>



 Bob,

 Thanks for your comments.  I am really proud of this project, but did not 

 expect many replies because GPS has made dead reckoning obsolete.  You and 

 another friend suggested using a PIC micro-controller.  Unfortunately I 

 know very little about them.  I understand that a programmer is required. 

 It was fun learning how to program the CD74HC4059 counter-divider. 

 Learning how to program a PIC micro-controller should be fun too.

   There's a ton of pic development systems out there

   for under $100, dozens for under $50. You might

   think about subscribing to Nuts and Volts magazine



 http://www.nutsvolts.com/



   Their advertisers include a number of hobbyist PIC

   systems to get started with. The one we use here is

   only $29 and comes with an exceedingly capable editor,

   assembler package. I think it's the PicKit II. You can

   go the assembler route (I think there's only 35 instructions

   to learn how to use) or the Tiny Basic round offered in

   the Basic Stamp series systems . . . and others.



 http://www.parallax.com/



 http://www.parallax.com/Resources/GettingStarted/tabid/270/Default.aspx



  There are programmers listed on eBay from $15 to over $200.  Does anyone 

 have a suggestion on which one to buy?



   This one is $100 but probably your best bet to get

   up and running quickly in Tiny Basic or Assembler



 http://tinyurl.com/yfxgka4



   See also:



 http://www.mstracey.btinternet.co.uk/pictutorial/picmain.htm



 http://tutor.al-williams.com/pic-intro.html



 http://www.hobbyprojects.com/microcontroller_tutorials.html

   I want to build a capacitance to voltage converter for a fuel gauge like 

 this:http://www.rstengineering.com/kitplanes/KP0007/KPsch.jpg

 Can a PIC micro-controller replace much of that circuit?



    Oh my, yes. I've been halted on a program to do just that.

    The program manager ran out of money. It might come back

    in the spring . . .



    The philosophy I'm using alternately charges the

    tank capacitance through a large value resistor

    and discharges it with a transistor. The time it takes

    to charge the capacitor from zero to some reference

    value is measured by the uP. Every other charge/discharge

    cycle, a 100 pf reference capacitor is switched across the

    tank line and the time to charge total capacitances is

    measured.



    By having a reference capacitor, calculation of tank

    + wiring capacitance is a simple ratio that wipes out

    errors in charging current or comparator trip voltages.



    System accuracy is dependent only on stability of

    the reference capacitor and timing accuracy of the uP

    (crystal controlled).



    I can't offer you anything more than that right

    now but I  can assure you it's well within the capability of

    the PICs to do the timing, operating the capacitor

    switch and calculating a PWM output value that

    represents % of tank contents. What's more, the

    total parts count is VERY low.



    Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jan 12, 2010 12:14 pm Post subject: Electronic Dead Reckoning Distance Calculator

At 08:38 AM 1/12/2010, you wrote:

 	  Quote: 	
		  



To Peter, Bob, Ken, Ed,

   I know that I can build that capacitance-to-voltage-converter 

 fuel-gauge circuit designed by Jim Weir using discreet parts that 

 do not cost very much.  Using a PIC microcontroller will cost more 

 in both time and money to purchase the programmer and to learn how 

 to use it.  On the other hand, new technology is exciting and it 

 will be fun to learn a new skill that can be used for future 

 projects.  Thanks for your suggestions and advice.


	




    Certainly going the discrete component route has some

    educational value . . . as I mentioned, I have plans

    for my grandsons to sling a little solder over some

    vacuum tubes. I've looked at the schematic in Jim's

    article. It's not clear to me that it even works.



    There are two oscillators . . . U101A and U101C

    who's frequency is set by hysteresis (resistor network

    on the minus terminal) and the RC time constant of

    network on the plus terminal.



    The frequency of the lower oscillator is fixed.

    The frequency of the upper oscillator is affected

    by the 360 pF variable which I presume is tank

    + wiring capacitance. The output of both oscillators

    is fed to positive peak following integrators and

    then applied to a differential amplifier and finally

    to a gain stage U102B. Offset and gain potentiometers

    are provided in the DC gain stages.



    It appears that the circuit depends on a DIFFERENCE

    in relative duty cycle of the two oscillators. While

    they differ from each other in frequency, their duty

    cycles will be close to 50% irrespective of frequency.

    The stages at U101B and U101D are not frequency

    discriminators. I'd like to enlist the assistance

    of other electron-herders on the list to confirm

    or correct my dissection of this circuit's functionality.



    If you're up to the task for conducting the experiment,

    you  might consider this schematic:



http://aeroelectric.com/Pictures/Schematics/Fuel_Capacitance_Meter.pdf



    This circuit was crafted to generate a variable

    DUTY CYCLE as tank sensor capacitance changes.



    Like any analog circuit, calibration stability

    is subject to the sum total of effect contributed

    by every nearly every component in the system.

    This circuit was never built but it was analyzed

    for component effects on the system error budget.



    It's possible to build a practical fuel gage but

    falls short of the best we know how to do. This

    is why I move off to the processor-based design

    I described earlier . . . parts count and effects

    of those parts on calibration and drift are a

    TINY fraction of the analog.



    Let's see if anyone else on the List can confirm

    that the Kitplanes article fuel gage can be expected

    to meet design goals.



    Bob . . .





 	  Quote: 	
		  Joe



--------

Joe Gores





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 81163#281163




	




        Bob . . .

                    ////

                   (o o)

    ===========o00o=(_)=o00o=========

    < Go ahead, make my day . . .   >

    < show me where I'm wrong.      >

    =================================

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