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Thread: A Simulated Analog Display Using Two LEDs

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    Supporting Member rgsparber's Avatar
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    A Simulated Analog Display Using Two LEDs

    The gas gauge on my car shows Full, has a tick mark at half, and indicates Empty. Although spartan, this is all the precision I need. Using this idea, I found a way to use two LEDs to indicate how much charge remains in my eBike's battery.

    If you are interested, please, click here.


    Your comments are welcome. All of us are smarter than any one of us.


    Thanks,

    Rick

    173 Best Homemade Tools eBook
    Rick

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    Thanks rgsparber! We've added your Battery Charge Display to our Electronics category,
    as well as to your builder page: rgsparber's Homemade Tools. Your receipt:




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    nova_robotics's Tools
    Check out LM3914 bar graph LED drivers.

    https://www.ti.com/lit/ds/symlink/lm3914.pdf

    It's an absolutely amazing little chip. It needs almost no external components, and will give you a 10 LED bar graph of whatever voltage you're trying to measure. There's a sense pin that measures voltage, there's a low voltage pin where you apply the lowest voltage you want to display, and a high voltage pin where you want to apply your highest voltage. And it comes with an internal voltage reference so you can easily create these voltages. Then the chip will divide the highest and lowest voltages evenly and display them on the LEDs. Super amazing. I used to use them for makeshift speedometers, battery meters, and O2 sensor gauges.

    Also it's totally analog so there's no programming, and the refresh speed is generally much faster than a uC.

    And if you want to get really advanced you can daisy chain multiple LM3914s together to get bigger displays (the chip has provisions for this, because it's just built around a resistor divider network).

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    Supporting Member rgsparber's Avatar
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    rgsparber's Tools
    Quote Originally Posted by nova_robotics View Post
    Check out LM3914 bar graph LED drivers.

    https://www.ti.com/lit/ds/symlink/lm3914.pdf

    It's an absolutely amazing little chip. It needs almost no external components, and will give you a 10 LED bar graph of whatever voltage you're trying to measure. There's a sense pin that measures voltage, there's a low voltage pin where you apply the lowest voltage you want to display, and a high voltage pin where you want to apply your highest voltage. And it comes with an internal voltage reference so you can easily create these voltages. Then the chip will divide the highest and lowest voltages evenly and display them on the LEDs. Super amazing. I used to use them for makeshift speedometers, battery meters, and O2 sensor gauges.

    Also it's totally analog so there's no programming, and the refresh speed is generally much faster than a uC.

    And if you want to get really advanced you can daisy chain multiple LM3914s together to get bigger displays (the chip has provisions for this, because it's just built around a resistor divider network).
    It is a great device but doesn't fit my needs. My total currrent allocation is 6 mA and this device uses at least 7 mA per LED. If I went with a bar graph interface, I would use the ATTiny-83 and drive one LED at a time or mutliplex them and accept the lower intensity. I also don't have a voltage to measure since the quantity to be displayed is generated by the software running on the ATTiny-84.

    Rick



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