Motion Sensor Chips

Are obviously quite cheap these days. We had a new cable TV box a couple of years back and I couldn’t help notice the buttons light when I first picked it up. Very handy when the lights are low. I’ve just recently bought a new toothbrush and this also lights if you pick it up. What next I wonder?

What is the working principle of these, presumably solid state, devices?

MEMS accelerometers. You can get a 9-axis sensor from the likes of Bosch or Invensys for not a lot of money. 3 accelerations, 3 rotations (gyros), 3 magnetic. Most smartphones have them now.

John Haine:

You are a mine of information!

I gather that MEMS are "micro electro mechanical systems" so I assume that there is something in them that moves.

It is just an etching and plating process within a semiconductor. Say after laying down a plated layer of metal track with a lump on the end (for weight) they then etch away the support having used material that can be etched without eating the metal. So it end up with a bit of metal sticking out in mid air. This is on a microscopic level. It will vibrate up and down when the support is moved.
They have also built in to the semiconductor a strain gauge on the support so it can detect the vibration movement. Build lots of them in different directions during the chip fabrication process.

Thanks, Bazyle - very informative and I bet that "not many people know that"!

To make a gyroscope I think they make a u-shaped cantilever that is "released" from the substrate and made to vibrate up and down. Rotation around an appropriate axis causes it also to twist which can be detected separately.

I think my wife has had one secretly implanted into my nether regions, as soon as my bum touches the sofa she receives a signal and finds me something to do!

It’s probably just a simple pressure pad under the sofa.

Clearly an ideal subject [no, not Dave Wooton’s nether regions] for Scanning Electron Microscopy … so try a Google search for mems sensor sem image and admire the ‘craftsmanship’

MichaelG.

You can easily get hold of one to play with, for instance many of the introductory kits available for the Arduino include one, along with temperature sensors and other fun devices to play with. No soldering required you just hook the devices up with a breadboard. Some of the chips include a magnetic compass as well.

John

My latest clock has an Arduino Nano33BLE that has Bluetooth and a 9-axis sensor built in.

That sounds like a particularly complicated way to pick up pendulum motion