Lego NXT creations are even cooler with WiFi on board


The folks at Dexter Industries have just wrapped up a week of Lego NXT projects, most of which centered on the use of their NXT WiFi sensor. Developed over the last few months, the group has been hard at work refining their design and getting some of the kinks worked out, so now you too can control your NXT creations sans wires.

The demonstrations have covered various topics throughout the week, starting out with a short tutorial on how to use a computer to communicate with the NXT device using the TCP protocol. After taking a look at WiFi power-saving capabilities, they touched on pinging other networked machines as well as querying DNS records from an NXT device. An NXT-based webserver was the next project on the list, as was remote robot control over the Internet. Finally, they wrapped the week up by configuring their Lego robot to send a tweet.

If getting your NXT creations on the move with full-fledged network access is something that sounds interesting, be sure to check out their site for downloads, a WiFi manual, and more.

Video: Working with the 3pi robot’s line sensors

This week, we are serving up part five in our series where we are using the Pololu 3pi robot as a fancy development board for the ATmega328p processor. This week we are taking a quick break from working with the perpherals specific to the processor and will show how to work with the 3pi’s line sensors. A quick look at the schematic for the 3pi might lead you to think that you should be reading the line sensors with the A2D peripheral. Even though they are wired to the A2D pins, they need to be read digitally. In the video, [Jack] will show how to read raw values from the sensors and then how to calibrate the results so that you can get a nice clean 8-bit value representing what the sensors are seeing. Of course, that would happen under normal circumstances. Murphy had his way in this video and it turned out that our studio lighting was interfering a bit with the sensor readings when we were shooting so we didn’t get as good of a calibration as we would have liked when we shot.

Video is after the break.

In case you have missed the previous videos here are some links:

Part 1: Setting up the development environment
Part 2: Basic I/O
Part 3: Pulse Width Modulation
Part 4: Analog to Digital conversion

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Adding RS232 to a multimeter the hard way

You might want to store information from a multimeter to be graphed over time. This comes with pretty much all of the high-end professional models. But if you buy a super cheap meter you can bet this isn’t an option. [Jazzzzzz] has found a way to pull the data from a $4 meter via RS232. It’s not impossible, but we definitely think he’s doing it the hard way. That’s because he’s not just tapping into a dormant feature. He’s actually adding a microcontroller to sample the data and push it via the RS232 protocol.

On the bright side, this is easier than building a multimeter from scratch. The sampling circuits are still being used, with a PIC 16F688 intercepting the signals as they enter the stock microcontroller. The signal he was after comes into the chip on just one pin, but to get the readings right on the PIC he had to use an OpAmp. That’s only part of the puzzle as he also needed a way to tell what the selector switch was set at. In the end, adding a potentiometer and reading its value let him calculate the position.

[Thanks Karl]

Ghostly images appear thanks to projections on fog

This wire-frame cube appears to be floating in mid-air because it actually is. This is a project which [Tom] calls a Laminar Flow Fog Screen. He built a device that puts out a faint amount of fog, which the intense light from a projector is able to illuminate. The real trick here is to get a uniformed fog wall, which is where the laminar part comes in. Laminar Flow is a phenomenon where fluids flow in a perfectly parallel stream, not allowing errant portions to introduce turbulence. This is a favorite trick with water.

[Tom's] fog screen starts off with a PC fan to move the air. This airflow is smoothed and guided by a combination of a sponge, and multiple drinking straws. This apparatus is responsible for establishing the laminar flow, as the air picks up fog from an ultrasonic fogger along the way.

The only real problem here is that you want the projector shooting off into infinity. Otherwise, the projection goes right through the fog and displays on the wall, ruining the effect. Outdoor applications are great for this, as long as there’s no air movement to mess with your carefully established fog screen.

You can find a short test clip embedded after the break but there are other videos at the link above.

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Weekly Roundup 11/12/11

In case you missed them the first time around, here are our most popular posts from the past week:

In the #1 spot, we had a post about a tri-color laser projector that really is a well-done project. This projector sweeps the lasers around in vector mode using a pair or mirror galvanometers so would be perfect for playing asteroids in vivid full color!

In at #2 is a post about a PVC pipe gun that can shoot AA batteries at 600 batteries per minute!

Next up we have a post about the US military finding that due to Chinese counterfeit electronics, some of its weapon systems are defective. This has become a more serious issue in recent years. It has effected hackers too as shown in this Sparkfun post from last year.

After that, we had a post about a novel and somewhat scary way to post bulletins on a board without using tacks. How do they do that? By carefully using 20,000 Volts! Yikes. We’ll stick to tape next time we run out of tacks thank you very much.

Finally, we have one about a spot welder built out of some super capacitors and carbon rods. This one probably produces equally large sparks where it is welding and at the triggering mechanism!