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Thread: Building your (my) own electronic speedo

  1. #16
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    Quote Originally Posted by Badcat
    i'd buy one (if it wasn't to expensive)
    I don't think it would cost much - probabaly $40-50, but when you add packaging on... well its time to start running.

  2. #17
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    Hey I've got a few unrelated questions you might be able to answer? I've been toying with the idea of datalogging using the BS2 as I have a few of them lying around.

    What format does the tacho signal come across as? I see you tidy up the signal into a pulse input in your bottom left diagram. Do you then measure the time between pulses to calculate RPM or does the PIC have a function for this which returns a value?

  3. #18
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    That is awesome. How do you learn this electronics stuff?

  4. #19
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    Quote Originally Posted by Hoon
    Hey I've got a few unrelated questions you might be able to answer? I've been toying with the idea of datalogging using the BS2 as I have a few of them lying around.

    What format does the tacho signal come across as? I see you tidy up the signal into a pulse input in your bottom left diagram. Do you then measure the time between pulses to calculate RPM or does the PIC have a function for this which returns a value?
    Calculating the revs by the time between pulses requires division... trying to do that in assembler on an 8 bit micro which doesn't even have a multiply instruction

    I cheated - I count the number of pulses (4 pulses per revolution for the CBR250 - it has an output transistor which pulls the line high - there is nothing to push it low) in a 0.3 second interval and multiply it by 50. Gives me a number between 0 and 17,200 with increments of 50 - the real rev limit is at 17,230 so its pretty good. Could use any time period with 1ms increments - the longer the time the more accurate the rev reading but less frequent updates and vice versa.

    I do a similar thing for the speedo - count the number of holes in the disk brake that go past in a 0.432 second interval and thats my speed in km/h.
    Example (my bike): 15 holes per revolution, 1.8m around (its really 1798mm, but 1800mm is close enough). So for 100 pulses in 0.432 seconds = 231.48 pulses per second /15 = 15.43210 wheel revolutions per second * 1.8m = 27.77777m/s. multiply by 3600 for seconds to minutes and divide by 1000 for m to km and you get 100km/h - the same as the number of holes which went past. Very little math involved! Each hole equates to 12cm travelled, so if I wanted to, I could increment the odo every 12cm.

    I just noticed because of your post that I hadn'y put all the tacho cleanup stuff on there - there is extra cap in there now.

  5. #20
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    Quote Originally Posted by alarumba
    That is awesome. How do you learn this electronics stuff?
    Spend faaar too many years of your life (7) at uni doing two degrees in Electrical & Electronic engineering. Actually a single degree would be enough.

  6. #21
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    For those of you with an extraordinary budget though you could consider this.
    http://www.veypor.com/
    I would call this the ultimate performance type accessory thingy. Mine is on its way.

    "If you can't laugh at yourself, you're just not paying attention!"
    "There is no limit to dumb."

    "Resolve to live with all your might while you do live, and as you shall wish you had done ten thousand years hence."

  7. #22
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    Quote Originally Posted by FlyingDutchMan
    I'm not quite sure how lap counters work (rider pushes a button or is there an RF signal or what?), but water temp can be done... just have to re-arrange the wiring to free up an Analogue input pin.
    The simpleist lap timers/counters work off a button on the bars (like a stopwatch) but a RF transmitter could be set up on the side of the track if one was available cheaply enough. Perhaps you could make them too? I am interested in a basic lap timer/counter. Can you come up with a price for a complete unit? It would need a large (ish) display so it could be read while on the bike.
    Cheers
    Ian

  8. #23
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    Quote Originally Posted by FlyingDutchMan
    I don't think it would cost much - probabaly $40-50, but when you add packaging on... well its time to start running.
    well - if you want to build them - i'm your first customer.
    k
    I am Jack's complete lack of remorse .

  9. #24
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    Quote Originally Posted by Aiolos
    Why do anything yourself?
    Why cook? Why shower?
    Why ride an NC30? You would get there much faster on a litre biker.

    What speed do bicycle speedos max out at?
    Bicycles speedo have small displays generally, and no tacho, which FlyingDutchMan's design does.
    This design is also customisable, and I like cowboyz' idea.
    Speedo-199 kmh
    Max speed-999 kmh
    And the display size is fine,I have used one as my sole speedometer for years,and before you say it, if you are doing 200 kmh+ and looking to see what your speed is you are an idiot.Besides the max speed function takes care of that.

  10. #25
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    Quote Originally Posted by FlyingDutchMan
    I don't think it would cost much - probabaly $40-50, but when you add packaging on... well its time to start running.
    im the same as badcat. if you start making them im highly interested

  11. #26
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    Seems I might have to get some PCBs made up so I can produce a professional looking unit. I'll have to upgrade from the black duct tape packaging I'm currently using though - even if it does look classy.

  12. #27
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    12th July 2003 - 01:10
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    Quote Originally Posted by FlyingDutchMan
    Seems I might have to get some PCBs made up so I can produce a professional looking unit. I'll have to upgrade from the black duct tape packaging I'm currently using though - even if it does look classy.
    Ha ha, yeah, the duct-tape gave it that 'temporary' (you call it 'classy'?) look alright - but it all worked well, I was impressed. (can you make one that will get my Sporty to rev to 17,000rpm??? )
    Winding up drongos, foil hat wearers and over sensitive KBers for over 14,000 posts...........
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