Hi-Tech Tool For Measuring Your Kid’s Height

Sure we can have our kids back up against a wall, force them to stand up straight, and use a ruler on their head to mark their height on the wall, but what kind of hacker would we be? There isn’t a single microcontroller or any electronic component involved! The DIY-family that calls themselves [HomeMadeGarbage] stood tall and came up with a high-tech tool to measure their kid’s height.

In place of the ruler they got a small wooden box to place on the head. Under the box, at the rear end facing down, they mounted a VL53L0X laser ranging sensor. With a range of 2 meters it’s sure to work with any child. But the box has to be sat level on the child’s head, otherwise the laser will be pointing down at an angle. To handle that they put an MPU6050 6-axis motion sensor in the box along with an Arduino Nano to tie it all together. A LCD display, measurement push-button and LED are mounted outside the box on the rear facing side.

To use it, a parent sits the box on the child’s head, making sure the laser sensor isn’t blocked and can see the floor. The LCD shows the height, along with the acceleration in the x and y directions. The LED is red if the box isn’t level and green if it is. Holding the measurement button pressed puts the tool in measurement mode and when it’s level, the LED turns blue and the LCD display freezes so you can make a note of the height. You’re good for a while, depending on your child’s age. See it being used to measure a child after the break as well as an additional clip showing what the output looks like when waving a hand up and down below it.

Here they measure their child’s height.

And here’s the output when raising and lowering a hand below the sensor. The x and y values are acceleration values from the motion sensor.

And while on the topic of measuring our children’s parameters, check out this Robo Doc that reads children’s pulses without scaring them.

[via hackster.io]

22 thoughts on “Hi-Tech Tool For Measuring Your Kid’s Height

  1. This is a really neat project. But if I’m reading the datasheet correctly, the VL53L0X is only accurate to within several centimeters! It seems as though the color and texture of the target (floor) might affect accuracy as well.

    I would want to see a long-term comparison against traditional measurement methods before trusting this device for a historical record.

    1. I agree, I got excited about this as I’ve been looking for a laser range finder for all sorts of projects :-) as ultrasonic (cheap) is a bit rough.
      However, I too went and looked at the data sheet, and apart from the 1.8v being not good (can’t just plug it into a 8266…) the accuracy seemed below a $3 ultrasonic unit… ie from the graph it’s at least a few cms…

      The thing I find most annoying is that you can buy a cheap laser range finder from your local hardware, but I can’t seem to find a cheap chip to do the same in my projects…

  2. You can get a much better measurement with a laser measuring tool by using multiple bounces off mirrors, just divide the result by the number of paths. The trick is getting the right geometry. It should prove much more accurate, but no less pointless, seriously we have a tribe of kids here and my partner has multiple post grad level medical qualifications but sees no point in measuring anything about our kids. They either look and behave right or they don’t, anything else is irrelevant natural variation. If something about them is completely away from normal, when it is obvious, then you start monitoring.

    1. No point? Wow you like taking the fun out of your kids lives don’t you.

      No one measured their kid for medical reasons. We measured them to see their faces light up when they see they got taller, we measured them to see them reminisce when they still see the markings on the wall years down the line.

      Maybe it’s time you get a post grad degree in fun.

  3. Hmmm could you measure height by flipping a scale upside-down on the ground and zeroing it then place it again upside-down on someones head (or whatever you want to measure) and use the measured weight difference to calculate the height? I guess precision would be very very poor.

    1. The accuracy of this mode depends on the house. In some rooms we had several cm deviation in the ceiling height. But we used the traditional method: Standing against a doorframe (parents watching to detect cheating like tip-toeing :-) ), marking the height and using a tape measure.

  4. There is one thing you will be missing with this hi-tech: in 10 or 15 years you WILL NOT have a wall scribbled with all the markings, year after year, of your children’s growth.
    Priceless (for a parent)

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