An accelerometer is the ubiquitous little sensor that tells your tablet when to flip orientation or informs the brain of your quadcopter how closely its actual actions are matching your desired ones. In a quick three minutes, [Afroman] explains what is inside an accelerometer and how they work.
It turns out the tiny devices that report acceleration in one, two or three dimensions are not powered by magic complicated mechanisms but very simple Micro Electro-Mechanical Systems or “MEMS.” MEMS are similar to copper/silver/gold-wired integrated circuits except in a MEMS circuit conductive silicon is used and they actually physically move, but only just a bit.
The secret is in creating microscopic capacitors along a weighted lever that flexes in response to changes in velocity. When the plates flex the distance between them changes which alters the capacitance. This translates physical motion into voltage which can then be interpreted by the rest of your circuit. The chemistry behind MEMS is interesting too.
This Christmas when your laptop’s power cord clotheslines your cousin’s kid, your hard drive has a chance of parking the head (on the drive, not on the child) between fall and impact and preventing damage (to the drive, not to the child) because of an accelerometer. If bad roads cause you to drift into the ditch, it is an accelerometer that senses the crash and tells your airbag to deploy before your body hits the steering wheel.
The MEMS market is exploding right now and for us hackers in particular, Wearables are looking to be a big part of that growth.
A gyroscope is a device made for measuring orientation and can typically be found in modern smartphones or tablet PCs to enable rich user experience. A team from Stanford managed to recognize simple words from only analyzing gyroscope signals (PDF warning). The complex inner workings of MEMS based gyroscopes (which use the Coriolis effect) and Android software limitations only allowed the team to only sniff frequencies under 200Hz. This may therefore explain the average 12% word recognition rate that was achieved with custom recognition algorithms. It may however still be enough to make you reconsider installing an app that don’t necessarily need access to the on-board sensors to work. Interestingly, the paper also states that STMicroelectronics currently have a 80% market share for smartphone / Tablet PCs gyroscopes.
On the same topic, you may be interested to check out a gyroscope-based smartphone keylogging attack we featured a couple of years ago.
Hackaday alum [Adam Munich] shot a tutorial video on using a rate gyroscope.
Here he’s showing off the really fancy piece of ancient (technologically speaking) hardware. It would have set you back about fifteen grand in the 1960’s (inflation adjusted) but can be had these days for around $30. What a deal! These are not small, or power efficient when compared to the components that go into smart phones or gaming controllers, but they’re a heck of a lot more accurate than the ubiquitous modern parts. That’s because a rate gyroscope — which is the gold cylinder on the left — actually incorporates a spinning motor and a way to monitor how it is affected by changes in gravity. The driver/interface circuitry for this gets hairy relatively fast, but [Adam] does a solid job of breaking down the concept into smaller parts that are easy to manage.
Wondering what is different about this compared to a MEMS accelerometer? We know they’re really not the same thing at all, but wanted a chance to mention [The Engineer Guy’s] video on how those parts are made.
Continue reading “Rate Gyroscope circuitry explained”
The Nyan Cat you see above is only 600 micrometers from head to tail. To put that into perspective, that’s about 10 times the diameter of a human hair. Also, that Nyan is etched into 200 nanometer thick copper foil and is the work of the HomeCMOS team, who is developing a hobbyist-friendly process to make integrated circuits and MEMS devices at home.
The project is far from complete; HomeCMOS has yet to produce a working IC but a few experiments – getting wet etching down pat and even building an almost working quantum qbit – are remarkable given the small amount of equipment and tools involved.
The HomeCMOS team has yet to actually make an integrated circuit or MEMS device, [Jeri Ellsworth] has shown this is possible by making transistors and integrated circuits at home. While there won’t be chips with millions of transistors coming out of the HomeCMOS lab anytime soon, it’s more than possible to see a few small-scale integration-level tech such as a few logic gates or a regulator.
A friend of [CNLohr’s] used the mechanism from an old pocket watch in an art piece, but left him with the enclosure. It’s an interesting looking object that feels great in your hand so he decided to fill it with his own electronics, thereby giving it a new life. He’s showing off an early version of the hardware in the video, but plans to send off another version of the board soon to add a few features.
You can see that the round PCB is small enough to fit in the space vacated by the original hardware. The ribbon cable is used to connect to the programmer and we think it’s also the power source for this demonstration. There’s a small Densitron display that’s reading out hex values from the accelerometer. Many of these mems chip (you can learn how they work from this post) include a hardware tap detector. This meant you can tap your finger on the device and the chip will signal an input to whatever chip is attached to it. That’s a great option for user input, and it’s what [CNLohr] chose as the select button here. He tilts the watch to one side, then taps to turn on the LED. That’s all for now, but we like the promise it shows and can’t wait for updates!
Continue reading “Pocketwatch retrofit takes input from accelerometer”
There’s a good chance that you use a MEMS accelerometer every single day. It’s the small chip that let your smart phone automatically adjust its screen orientation. They’re great chips, and since they’re mass-produced you can add them to your projects for a song (if you can abide the tiny packaging). But we have no idea of how they are made and only a inkling of how they work. [Bill Hammack] has filled that knowledge gap with this explanation of how MEMS accelerometers are made and how they function.
Our base knowledge comes from the acronym: Micro Electro-Mechanical Systems. There’s something in the chip that moves (so much for solid state electronics; and it makes us wonder if these wear out). [Bill] includes a diagram in his video after the break which shows the silicon-based system that moves as it is affected by gravity. This changes the capacitive properties of the structure, which can be measured and reported to a microcontroller for further use. The structure is built using an intricate etching process which we never want to try out at home.
Looking for a project in which to use one of these devices? We’ve always been fond of this POV device.
Continue reading “The Engineer Guy explains how MEMS accelerometer chips work”