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Thread: HUD speedometer

  1. #21
    Variable Bitrate
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    Quote Originally Posted by sxtnitehawk View Post
    I know it's a little late for this suggestion...but does anyone know if there's a binary driver that could convert a 1byte signal into a numeric display? You could cut the number of outputs used in half with a max speed of 255...

    god i feel like a geek again lol

    i like what you've done though
    At that point, it would probably be easier to use an EEPROM or something. the 8-bit number in as address, and the data out driving the LED's. Have to make up the table, and burn it into the chip, but it should work quite well once burnt.
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  2. #22
    Raw Wave
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    I think at that point, the FB is the wrong device - there are various tacho/speedo circuits that can be used.

    Multiplexing the FB will reduce the outputs to 10 (3 digits).

    Otherwise for binary, do you mean BCD, byte/word conversion, or serial? But add one chip to that and you save the FB.

  3. #23
    What can I say? I like serial. Curiosity's Avatar
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    That's called a shift register. It has a sort of memory. A lot of the big matrix signs use them as 7-bit chained using the last bit to send data to the next. You can control a lot of LEDs with just a few lines.

  4. #24
    Raw Wave
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    If you want to rotate the display, yes - that's a shift register.

    I was writing about full drivers....

  5. #25
    Fusion Brain Creator 2k1Toaster's Avatar
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    You can look into demultiplexers if you want to save outputs. Change the outputs fast enough and nobody will know that only one segment is on at one time.
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  6. #26
    What can I say? I like serial. Curiosity's Avatar
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    Quote Originally Posted by OldSpark View Post
    If you want to rotate the display, yes - that's a shift register.

    I was writing about full drivers....
    It might be possible to shift but the main purpose is serial to parallel conversion. The 8 bits are shifted in, then it switches to the new bit set. They also have enough power to drive LEDs and without resistors using the correct voltage. They work quite well.

  7. #27
    Fusion Brain Creator 2k1Toaster's Avatar
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    Yeah a SIPO would work fine. For ease of use you can use the 74LS series of chips.
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    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
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  8. #28
    Raw Wave
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    On multiplexing and resistorless LEDs....

    SiliconChip August 2010 features a 6 digit (remote controlled up/down) timer.

    It uses a total of 10 lines for its 6 digits (including power).
    10 ATINY ports multiplex the segment anodes & cathodes directly.

    They do not use resistors. Despite exceeding the LED current, the duty cycle keeps it under their pulse current tolerance (something Curiosity and others are familiar with).

    Cute eh? 3 more digits than the above, 6 less ports, and (probably) 8-16 less resistors.
    Using this method they achieve a constant brightness across all digits.

  9. #29
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    Has anyone considered trying to use a Projector as a HUD?

  10. #30
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    Have considered it, using a pico-projector such as the Acer C120, Acer K11 or K130.
    Issues:
    Probably not visible in broad daylight. (have tried with a 15 lumen projector - it might work at night with the headlights off, but that wouldn't be very useful, would it?)
    The minimum focus distance for those projectors are 40-60 cm, so it would require some sort of mirror setup or mounting the projector somewhere near the seats.
    The windscreen is usually not flat, so the display might look pretty distorted.
    Even if the other issues are overcome, there is still the "double-reflection" to sort out.

    A laser projector does not need focusing and might be an idea.
    You could look at this : http://www.microvision.com/solutions..._displays.html - they have a dev. kit available for 1695 $

    Youtube also has a lot of HUD videos - however, I haven't found any DIY solutions that looked acceptable in daylight.

    Question:
    Would a LCD monitor with a massively overclocked backlight work as a HUD?

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