Micro controller Use

Discussion in 'General Electronics Chat' started by electric101, Apr 26, 2011.

  1. electric101

    Thread Starter New Member

    Apr 25, 2011
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    Hello,

    I am wondering; does a cruise control system use a micro controller? It would make sense to me that it does; but I'm not sure.

    I am looking to purchase a micro controller kit but want to know if a micro controller is what I need.

    It should be noted that this is NOT automotive related. The system I'll be mocking is automotive related, but it's not being installed in a car. Or anything that is street legal, for that matter.

    Any help would be great. Thanks!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Motorolla used to make an IC purpose made for cruise control. The ECU no doubt handles that function now.

    You can use all sorts of ways to do the function - analog and digital. It's a servo control that tries to keep an input (voltage or pulse frequency) steady.
     
  3. hgmjr

    Moderator

    Jan 28, 2005
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    It would help us to answer your question if you could be more specific about what you are planning to do with the microcontroller.

    Also, what experience have you had with programming? What languages have you programmed with? What is your approximate budget for this project?

    hgmjr
     
  4. electric101

    Thread Starter New Member

    Apr 25, 2011
    12
    0

    Thanks to both of you.

    Yes, I guess I should have expanded on the project. It will be installed on a go-kart style chase vehicle that we use to "camera shadow" vehicles on the salt flats. We do have a speedometer installed on the chase kart, but no ECM. It's a 250cc 4 stroke engine thrown into a chassis I welded up. Since what we are filming is done by the driver, we need the cart as "self-operational" as possible. Part of the beauty of the flats; nothing to run into. haha.

    Now, as far as the programming. I have no experience but am interested in learning. I've purchased a couple books regarding the programming; plan to start reading them soon. I can budget $300 for the speed control portion with the project manager. The PICAXE seems to be a good way to go; any thoughts?

    p.s. This is a no-rush project, plenty of time as our rights to film on the flats aren't until mid summer
     
  5. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    Picaxe is easy, but slow. It might not keep up with the speed sensor. Much more than 150Hz and it gets dicey. Arduino is >>quicker but might be not as easy to program. It has a huge following that can walk you out of any problem though.
     
    electric101 likes this.
  6. PRS

    Well-Known Member

    Aug 24, 2008
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    With your budget go to Jameco Electronics and buy a Basic Stamp and buy a book that tells how to use it. This would be the easiest way to make a smart controller such that you describe.

    But if you're serious about the future, then you want to use a PIC microcontroller made by Microchip. This is the real McCoy. In this case go to Microchip and buy a PICkit2 or PicKit3, and download all the software that goes with it. This is only if you're really serious about microcontrollers.
     
  7. hgmjr

    Moderator

    Jan 28, 2005
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    So your project is to design and build a cruise-control unit for this go-kart. The input signals you have are speed (from the speedometer) along with controls such as "increase speed", "decrease speed", "engage", and "disengage". The output would be a signal that would control the speed of the motor. Does that sound about right?

    hgmjr
     
  8. electric101

    Thread Starter New Member

    Apr 25, 2011
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    That sounds exactly right. And the controls don't have to be fancy. No style points here, just functionality!
     
  9. electric101

    Thread Starter New Member

    Apr 25, 2011
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    Thank you, great insight. I'll look into Arduino, I will end up leaning on the help, I'm sure.

    I'll look at both these. I'm into building things so I have to imagine that microcontrollers would be up my alley; therefore, the Microchip place might be the direction to go. Hmmm. Thanks!!
     
  10. BillO

    Well-Known Member

    Nov 24, 2008
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    How fast is the kart and what diameter are the wheels?

    A PICAXE may do it, but as already mentioned, and Arduino would be a better bet.

    You could do this with;


    Sounds like a neat project. Have fun!

    Edit: An RTC would be great too.
     
    Last edited: Apr 26, 2011
  11. electric101

    Thread Starter New Member

    Apr 25, 2011
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    0

    The kart can reach speeds of 90 mph but our typical chase speed is between 24 - 29 mph. Diameter of the wheels = 13". The kart is great fun to ride around on the flats on lunch break! ;)

    I'll look at the links provided, thank you. I was wondering if I would have to utilize a vacuum operated actuator or not for the control of the throttle, but it looks like I can get away without it. Which is good, seeing as I don't have much vacuum produced from that engine.

    Thanks again for the input.
     
  12. BillO

    Well-Known Member

    Nov 24, 2008
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    Well, with wheels that size (outside diameter), they will be turning less than 22 times each second at 50 mph. In which case a PICAXE will easily keep up for your application, so you can go either way, PICAXE or Arduino.
     
  13. BillB3857

    Senior Member

    Feb 28, 2009
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    You also need to be concerned with the physical actuator you will need to control the throttle. At one time, there were "add on" cruise controls available. They had a magnetic pickup added to the drive shaft with the magnets attached with a hose clamp, an electronic module and a vacuum actuator. The actuator had two electrically controlled valves built in. One allowed manifold vacuum to a diaphragm to increase throttle and the other vented air to the diaphragm to decrease throttle. With neither actuated, the diaphragm held the last commanded position. Here is a link to an installation manual for one......

    www.gadgetjq.com/av_manual.pdf
    For some reason, you need to copy and paste the whole link. Don't know why?????
     
    Last edited: Apr 26, 2011
  14. electric101

    Thread Starter New Member

    Apr 25, 2011
    12
    0
    Okay. If you don't mind, help me understand this. A previous post mentioned anything over 150hz and the PICAXE might not work. So how does the 22 revolutions a second at 50 mph compare to 150hz? Sorry for what seems like a rather dumb question! I suspect the books I've ordered will help with these types of questions, too. Nothing like learning through books!
     
  15. electric101

    Thread Starter New Member

    Apr 25, 2011
    12
    0
    Great info! I'm familiar with AV and suspect I'll end up purchasing some parts through them. I'm not sure about my vacuum pressure; if I have enough to work for the actuator; it states 6" of mercury or more at all times, so I'll check that next. May have to use a vacuum canister. Or go about it with a servo motor. Options options options....:)

    Thank you for the help!
     
  16. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    Auto wrecking yards have a wealth of parts cheap. GM had two flavors of cruise control actuator in the 90's, one vacuum operated and one electrical. Ford also had an electrical actuator in the 90's. If you don't have a wrecking yard near you, let me know and I will gladly get one or both of the electrical actuators for you.
    Here's how one guy modified a GM unit for his specific need:

    http://www.mwrench.com/barth/cruise control/Cruise Control.pdf
     
    Last edited: Apr 27, 2011
  17. hgmjr

    Moderator

    Jan 28, 2005
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    I suspect that you will probably be using a PID algorithm to manage the speed control. One nice thing about the Arduino is that there is already a library of functions for PID implementation.

    hgmjr
     
  18. t06afre

    AAC Fanatic!

    May 11, 2009
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    Cruise control have been around for many years. I think the early models were analog PID controllers. The first standard production car with drive by wire (engine speed not controlled by mechanical wire) came in 1989. But it was only Electronic throttle control. And it was then naturally to move the cruise control system into the ECU. To day almost all car use drive by wire and cruise control is part of the ECU.
    So in your project I think it will essential to use a drive by wire concept. And not using a mechanical engine control. But rather some servo system
     
    Last edited: Apr 27, 2011
  19. strantor

    AAC Fanatic!

    Oct 3, 2010
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    22 revolutions/ second (assuming you mount 1 magnet on the wheel, so 1 pulse per revolution) = 22hz. 1 Hz = 1 cycle per second.

    I don't really think that you need it, but if you wanted better speed resolution, you could mount more than 1 magnet. for example, if you planned to run < 1 wheel revolution/second (around 2.3mph), then you would be recieving less than 1 pulse per second, and your cruise control might act wacky because the calculated speed would be jumping all over. In this case you could mount say, 10 magnets on the wheel. If you had 10 magnets on the wheel and then you changed your mind and decided to go 50mph, then you would be at 220Hz and outside the capacity of the PICAXE.
     
  20. BillO

    Well-Known Member

    Nov 24, 2008
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    @strantor - Right! That's what I was going to say.:cool:

    @electric101 - The more I think about this, the more I think the Arduino is the best choice. You can get a "Sensor Shield" for it (less than $10) to easily connect up push buttons, sensors and servos. Plus, as stated, there is a wealth of libraries that cover what you need. It also has a nice pair of functions for timing purposes (micros() and millis()) that would make it a simple matter to determine the kart's speed by timing the rotation of the wheels.
     
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