RSS Feed

February, 2012

  1. SpeedoHealer V4

    February 25, 2012 by frank

    Well, ain’t that a bummer.  After going for my first testdrive, it turns out that my speedo is reading about 20% slow compared to my gps.  I could only do a short drive, but it immediately was very clear that the speedo is off.

    This means that the transmission is sending out 4000 ppm, not 4800 like I assumed.  I’ll have to use a 39 multiplier, something Jean’s board can’t do, so I’ll have to look for an other solution.

    I could program a pic to do the conversion, but this project has already taken too much of my time.  I’ve been messing about with VR circuits, voltage dividers and PWM converter circuits for too long.  I don’t want to spend several days designing a pic based circuit, building and testing it, buying a programmer to progam the pic etc.  So, I decided to take the easy and fast route and ordered a SpeedoHealer V4 today.  78€ well spent :) .

    Category Westield build diary | Tags: | No Comments

  2. got it working

    February 22, 2012 by frank

    Finally got it right. The speedo is working!

    I was sending a 9V signal into my PWM converter that can only handle 5.3V ... luckely I had 2 chips :)
    View at Picasa

    I was sending a 9V signal into my PWM converter that can only handle 5.3V … luckely I had 2 chips :)

    Turns out I was feeding my circuit with a too high signal.  The circuit can only handle 5V and I was sending 9V in it (oscilloscope was set to  ~AC in this pic).

     

     

    Speed conversion. Red is 5.6V input, blue is 5V output (freq x32). The chip can only handle 5.3V, so I need to lower the input a bit.<br /> 23.8Hz = 28km/u as indicated by TunerStudio
    View at Picasa

    Speed conversion. Red is 5.6V input, blue is 5V output (freq x32). The chip can only handle 5.3V, so I need to lower the input a bit.
    23.8Hz = 28km/u as indicated by TunerStudio
    Perfect! 5V square wave in (red trace) and 5V square wave out with x32 frequency
    View at Picasa

    Perfect! 5V square wave in (red trace) and 5V square wave out with x32 frequency

    After modifying the signal to 5.6V, it was working perfectly, but I didn’t want to take the risk of blowing up the chip, so I reduced it to 5V exactly.

     

    Category Westield build diary | Tags: | No Comments

  3. Partial success

    February 12, 2012 by frank

    I got the speedo working with a PWM signal generated by a generic output from the Megasquirt.  I then send this signal through a PWM converter with a 32 multiplier.  This generates a 499Hz signal that indicates a speed of 18km/u, what corresponds with what I calculated.  It was kinda cool to see the odo ticking forward.  I let the car run for 8.8km :) .  The speedo should be spot on :) .
    Unfortunately, I didn’t get it working in the car yet.  My transmission generates an AC signal that I convert to a square wave and send to the PWM converter.  Although it works with my self generated signal, it doesn’t work with the signal coming out of my VR converter.  It looks ok on the oscilloscope though.  I’m a bit puzzled, but I’m sure I’ll figure it out eventually.

    Category Westield build diary | Tags: | No Comments