Wafer level chips are cheap and very tiny, but as [Kevin Darrah] shows, vulnerable to bright light without the protective plastic casings standard on other chip packages.
We covered a similar phenomenon when the Raspberry Pi 2 came out. A user was taking photos of his Pi to document a project. Whenever his camera flash went off, it would reset the board.
[Kevin] got a new Arduino 101 board into his lab. The board has a processor from Intel, an accelerometer, and Bluetooth Low Energy out of the box while staying within the same relative price bracket as the Atmel versions. He was admiring the board, when he noticed that one of the components glittered under the light. Curious, he pulled open the schematic for the board, and found that it was the chip that switched power between the barrel jack and the USB. Not only that, it was a wafer level package.
So, he got out his camera and a laser. Sure enough, both would cause the power to drop off for as long as the package was exposed to the strong light. The Raspberry Pi foundation later wrote about this phenomenon in more detail. They say it won’t affect normal use, but if you’re going to expose your device to high energy light, simply put it inside a case or cover the chip with tape, Sugru, or a non-conductive paint to shield it.
EDIT: [Kevin] also tested it under the sun and found conditions in which it would reset. Videos after the break.
Continue reading “Don’t Take Photos of Your Arduino 101 Either, It’s Light Sensitive”
For the past month, the Raspberry Pi 2 has only been available to the Raspi Foundation, and for about 2 weeks, select members of the media who have worn the Raspi 2 on a necklace like [Flavor Flav] wears a clock. That’s not many people with real, working hardware and when a product is released, the great unwashed masses will find some really, really weird bugs. The first one to crop up is a light-sensitive reset of the Raspberry Pi 2.
[PeterO] on the Raspberry Pi forums took a few pictures – with flash – of a running Raspberry Pi 2. It took a little bit of deduction to realize that a camera flash will either reset or turn the Raspi 2 off. Yes, this is weird, and experiments are ongoing.
A short video from [Mike Redrobe] confirms the finding and a reddit thread offers an explanation. U16, a small chip located in the power supply part of the Raspi 2, is sensitive to light. Putting enough photons will cause the Pi to shut down or restart.
There’s still some research to be done, however, I can confirm a cheap green laser pointer will reset a Raspberry Pi 2 when the beam is directed at the U16 chip. This is the chip that is responsible, and this is not an EMP issue. This is a photon/light issue with the U16 chip. The solution to this bug is to either keep it in a case, or put a tiny amount of electrical tape over the chip.
Thanks [Arko] for staying up until an ungodly hour and sending this to me.
Some folks believe that exposure to electromagnetic pulses helps the human body heal itself (one portion of the [Bob Beck] protocol). [Steffan] is one of those folks and was interested in EMP generation but wasn’t crazy about the several-hundred dollar price tag for professional units. As any determined DIYer would do, he set off to make his own.
This whole thing works by straight-out-of-the-wall 110v AC running through a couple 60 watt light bulbs before moving through a rudimentary rectifier circuit. The DC output from the rectifier charges five 130uF camera flash capacitors. An inductor coil is responsible for generating the EMP and is only separated from the capacitors by a single normally-open momentary switch. Although it is possible to wrap your own coil, [Steffan] decided to use an off the shelf 2.5mH unit normally used for speaker system crossovers. Once the momentary switch is pressed, the energy in the capacitors is discharged through the inductor coil and the EMP is created. To demonstrate that the pulser does indeed work, a metal washer was placed on the inductor coil and the unit fired resulting in the washer being thrown into the air.
[Stephan] did deviate from the some of the online designs he had researched, using 7 capacitors instead of the recommended 5. The result was a firecracker-like discharge sound and melting of the 14 gauge wire. Well, back to 5 caps.
Last week we caught wind of a piece from the Today Show that shows very technically minded thieves stealing cars with a small device. Cops don’t know how they’re doing it, and of course the Today show (and the Hackaday comments) were full of speculation. The top three theories for how these thieves are unlocking car doors are jamming a keyless entry’s ‘lock signal’, a radio transmitter to send an ‘unlock’ code, or a small EMP device touched to the passenger side door to make it unlock.
That last theory – using a small EMP device to unlock a car’s door – got the attention of someone who builds mini EMP devices and has used them to get credits on slot machines. He emailed us under a condition of anonymity, but he says it’s highly unlikely a mini EMP device would be able to activate the solenoid on a car door.
This anonymous electromagnetic wizard would like to open up a challenge to Hackaday readers, though: demonstrate a miniature EMP device able to unlock an unmodified car door, and you’ll earn the respect of high voltage tinkerers the world over. If you’re successful you could always sell your device to a few criminal interests, but let’s keep things above board here.