An Optical Mouse Sensor For Robotic Vision

Readers with long memories will remember the days when mice and other similar pointing devices relied upon a hard rubber ball in contact with your desk or other surface, that transmitted any motion to a pair of toothed-wheel rotation sensors. Since the later half of the 1990s though, your rodent has been ever significantly more likely to rely upon an optical sensor taking the form of a small CCD camera connected to motion sensing electronics. These cameras are intriguing components with applications outside pointing devices, as is shown by [FoxIS] who has used one for robot vision.

The robot in question is a skid-steer 4-wheeled toy, to which he has added an ADNS3080 mouse sensor fitted with a lens, an H-bridge motor driver board, and a Wemos D1 Mini single board computer. The D1 serves a web page showing both the image from the ADNS3080 and an interface that allows the robot to be directed over a network connection. A pair of LiPo batteries complete the picture, with voltage monitoring via one of the Wemos analogue pins.

The ADNS3080 is an interesting component and we’d love see more of it. This laser distance sensor or perhaps this car movement tracker should give you some more info. We’ve heard rumors of them being useful for drones. Anyone?

Joe Grand is Hiding Data in Plain Sight: LEDs that Look Solid but Send a Message

Thursday night was a real treat. I got to see both Joe Grand and Kitty Yeung at the HDDG meetup, each speaking about their recent work.

Joe walked us through the OpticSpy, his newest hardware product that had its genesis in some of the earliest days of data leakage. Remember those lights on old modems that would blink when data is being transmitted or received? The easiest way to design this circuit is to tie the status LEDs directly to the RX and TX lines of a serial port, but it turns out that’s broadcasting your data out to anyone with a camera. You can’t see the light blinking so fast with your eyes of course, but with the right gear you most certainly could read out the ones and zeros. Joe built an homage to that time using a BPW21R photodiode.

Transmitting data over light is something that television manufacturers have been doing for decades, too. How do they work in a room full of light sources? They filter for the carrier signal (usually 38 kHz). But what if you’re interested in finding an arbitrary signal? Joe’s bag of tricks does it without the carrier and across a large spectrum. It feels a bit like magic, but even if you know how it works, his explanation of the hardware is worth a watch!

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High Speed Chronograph Looks Like Pro Gear

It can be hard enough to take a good photograph of a running kid or pet, and if we’re being honest, sometimes even stationary objects manage to allude our focus. Now imagine trying to take a picture of something moving really fast, like a bullet. Trying to capture the moment a fast moving projectile hits an object is simply not possible with a human behind the shutter button.

Enter the ballistic chronometer: a device that uses a set of sensor gates and a highly accurate timer to determine how fast an object is flying through it. Chronometers that operate up to a couple hundred meters per second are relatively common, but [td0g] had something a little faster in mind. He’s come up with an optical setup that he claims can capture objects moving as fast as Mach 2. With this chronometer tied into a high-speed flash rig, [td0g] is able to capture incredible shots such as the precise instant a bullet shatters a glass of water.

Because he couldn’t find any phototransistors with the sub-microsecond response time necessary to detect a small object moving at 1,000 m/s, [td0g] ended up using LEDs in a photoconductive configuration, where 27 VDC is applied backwards against the diode. Careful monitoring of voltage fluctuations across the diode allows for detection of changes in the received light level. To cut down on interference, [td0g] used IR LEDs as his light sources, reasoning there would be less ambient IR than if he used something in the visual range.

What really impresses with this build is the attention to detail and amount of polish [td0g] put into the design. From the slick angled bracket that holds the Arduino and LCD to the 3D printed covers over the optical gates, the final device looks like a professional piece of equipment with a price tag to rival that of a used car.

For the future, [td0g] plans on upgrading to faster comparators than he LM339’s he has installed currently, and springing for professionally done PCBs instead of protoboard. In it’s current state this is already a very impressive piece of kit, so we’d love to see what it looks like when it’s “finished”.

If you don’t need something quite this high end but still would like to see how fast something is going, we have covered chronometer builds to fit every budget.

DIY Optical Sensor Breakout Board makes DIY Optical Mouse

Wanting to experiment with using optical mouse sensors but a bit frustrated with the lack of options, [Tom Wiggins] rolled his own breakout board for the ADNS 3050 optical mouse sensor and in the process of developing it used it to make his own 3D-printed optical mouse. Optical mouse sensors are essentially self-contained cameras that track movement and make it available to a host. To work properly, the sensor needs a lens assembly and appropriate illumination, both of which mate to a specialized bracket along with the sensor. [Tom] found a replacement for the original ADNS LED but still couldn’t find the sensor bracket anywhere, so he designed his own.

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Turntable Turns Waveform Generator

In need of a waveform generator for another project, [David Cook] crammed out the old turntable to modify it for a handy hack: By adding a simple reflectance sensor to the pickup he turned it into a waveform generator that optically plays back arbitrary waveforms from printed paper discs.

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Single Molecule Detects Light

Everything is getting smaller all the time. Computers used to take rooms, then desks, and now they fit in your pocket or on your wrist. Researchers that investigate light sensors have known that individual diarylethene molecules can exist in two states: one where it conducts electricity and one where it doesn’t. A visible photon causes the molecule to be electrically open and ultraviolet causes it to close. But there’s a problem.

light600Placing electrodes on the molecule interferes with the process. Depending on the kind of electrode, the switch will get stuck in the on or off position. Researchers at Peking University in Beijing determined that placing some buffering material between the molecule and the electrodes would reduce the interference enough to maintain correct operation. What’s more the switches remain operable for a year, which is unusually long for this kind of construct.

Using chemical vapor deposition and electron beam lithography, the team produced over 40 working single molecule switches. These devices could be useful in optical computing and other applications. Future work will include developing multilevel switches comprised of multiple molecules.

If you want something more macroscopic, you might try using an LED to sense light. A switch is fine, but sometimes you want to generate a signal.