Color Sensing With An RGB LED And Photoresistor

December 8, 2011 by Mike Szczys 11 Comments

[Fjord Carver] brings together an RGB LED and CdS Photoresistor to make a color sensor. Those Cadmium Sulfide lights sensors usually have a very wide swing of resistance when exposed to varying levels of light sensitivity. That makes for great resolution when reading them using the ADC of a microcontroller. The LED comes into play by shining known wavelengths of light on the surface being measured. Three separate readings are taken with each of the LED’s different colors, then used to extrapolate the RGB value of the test material. We saw the very same method used a couple of years back. This time around it’s an Arduino doing the measuring instead of a PIC.

So why isn’t that sensor shown in this picture? It’s because we appreciate the application which [Fjord] is using for this sensor. He built a lamp that shines the same color as the surface on which it is placed.

Christmas Tree Water Sensor Gets An Upgrade And A Fancy New Box

December 7, 2011 by Mike Nathan 9 Comments

xmas-tree-water-sensor

[Eric Ayars] has a nice cast iron Christmas tree stand at home, but the only drawback is that the stand makes it hard to see just how much water is available to the tree. Last year we covered a small gadget he created to help keep tabs on the water level, but as several of you predicted, the system eventually failed.

His previous solution used copper plated proto board to sense how much water was in the stand, but the leads corroded in about a week’s time. With Christmas just around the corner, he decided to give things another try.

His revamped water level sensor relies on measuring capacitance changes in a copper strip board when under water rather than detecting a complete circuit like the previous model. To protect his sensor this time around he coated the board with polyurethane, which should provide a decent corrosion barrier.

Using the Arduino CapSense library, the sensor can detect the presence of water, signaling an alarm if the base needs refilling. One of our readers suggested that he use the tree itself as a low water indicator, which is just what [Eric] did this year. If the water is somewhat low, the Arduino-controlled relay powering the tree is switched off and then on again, every 5 seconds. If the base is nearly dry, the tree asks for water by blinking the word “Water” repeatedly in Morse code.

We think that this year’s solution is pretty clever, and we’re glad to see that [Eric] didn’t give up after last year’s setback!

An Iambic Keyer In 5 Minutes

December 5, 2011 by Brian Benchoff 17 Comments

When most people think about a telegraph key, a piece of 1890s tech with a lever that moves up and down comes to mind. These ‘straight keys’ were terrible for telegraphers and led to repetitive stress injuries like carpel tunnel syndrome..Iambic keys came along and move the contacts to a horizontal position. If you ever see a HAM playing with his CW rig, chances are they’re using an iambic key. It’s great, then, that you can build your own iambic key in five minutes using parts you have lying around.

The build [Dimitris] put up is dead simple – just two metal contacts with a pair of 470K pullup resistors. All this connects to three pins on an Arduino. All the micocontroller needs to do is measure the rise time a touch sensor pin when a voltage is applied. If there’s a finger on the pin, the capacitance increases and the rise time is longer. After that, just assign one sensor as ‘dit’ and the other as ‘dah’ and you’ve got an iambic key.

[Dimitris] put all the code for his project up on his blog. His iambic key seems like the perfect project after a tiny Morse trainer. Check out the video of the key in action after the break

Continue reading “An Iambic Keyer In 5 Minutes” →

Trying To Measure The Speed Of Light With An Arduino

December 1, 2011 by Brian Benchoff 63 Comments

We know that measuring the speed of light with an Arduino is possible. It’s just that the implementation is hard.

Last month we saw [Udo]’s blinkenlight shield that can be used as a line scan camera. It’s a neat piece of kit, but [Udo] really wants to submit something for the Buildlounge laser cutter giveaway, so he figured measuring the speed of light would be an easy project. If a kid and a chocolate bar can do it, surely it can’t be too hard.

[Udo] hit upon the idea of pulsing a laser pointer and measuring the time of the reflection. Because his blinkenlight shield can be used as a light sensor, all that’s needed is a mirror and a pretty long line of sight. There’s a few problems with the setup though: with the Arduino running at 16 MHz, a photon will travel 19 meters in one clock cycle.

Even with some very clever coding, we’re not really sure detecting an emitted photon is possible at such (relatively) slow clock speeds. We’re thinking [Udo] could source a few hundred meters of optic fiber so the entire experiment could fit on a desk, but feel free to drop a note in the comments if you’ve got a better idea. [Udo]’s demo of his blinkenlight/laser mashup is after the break.

Continue reading “Trying To Measure The Speed Of Light With An Arduino” →

Custom Massive LED Panel Lights Up The Party

November 30, 2011 by Mike Nathan 12 Comments

giant-led-sign

The guys at BuildLounge wrote us to share a giant LED sign they came across in the submission pile for their “Win a Laser Cutter” contest that’s currently under way. [Stephen Shaffer] helps run a huge party called Fantastic Planet, for which the group typically outsources the lighting arrangements. They got tired of hiring light guys several times a year and built their own mega display for the festivities instead.

The LED sign consists of 1,474 LEDs that output well over 10,000 lumens. The sign was produced for just about $800, which is very reasonable for a display of its size. The whole thing is controlled by a pair of Arduinos paired with 34 MIC5891 shift registers, all mounted on custom designed PCBs that the group produced in-house.

The display looks great, but don’t take our word for it – check out the video below to see it in action.

If you are interested in taking a closer look at how it was built, swing by the build thread to see more details.

Continue reading “Custom Massive LED Panel Lights Up The Party” →

Arduino Weather-station To Internet Bridge

November 30, 2011 by Mike Szczys 10 Comments

Here’s a project that looks to eliminate the PC necessary for pushing weather station data to the Internet. When you think about it, getting data from your own weather sensing hardware to a site like Weather Underground doesn’t require very much processing at all. The largest chunk of the puzzle is a window to the Internet, and that can be easily accomplished with a microcontroller rather than an always-on computer.

In this case, [Boris Landoni] is using an Arduino along with an RS232 shield and an Ethernet shield. The weather station, a La Crosse WS23xx series, already has an RS232 serial port for grabbing the data. The shield is necessary to step the voltage down to levels that will play nicely with Arduino. It also gives you a D-Sub connector for easy hook up. From there he hit up the documentation for Weather Undeground API, writing code to build the necessary string which is pushed over the Ethernet connection at regular intervals.

If your weather station only offers a USB port you’re not out of luck. Using an embedded platform with USB host functionality you can achieve the same results as we see here.

Graphical Programming With The Arduino IDE

November 30, 2011 by Brian Benchoff 46 Comments

The Arduino is an excellent first embedded development kit, provides a great introduction to electronics, and has the potential to get children into programming. [David] thinks throwing C at non-programmers isn’t the best way to learn programming, so he developed ArduBlock , a graphical programming language for the Arduino.

We’ve seen a number of graphical, block-based programming languages in our time, most notably Scratch. [David] found a project called OpenBlocks that serves as the basis for Android App Inventor.

[David] forked the OpenBlocks project and started working on his new graphical programming language. ArduBlocks uses the Arduino IDE, so everything possible in C with an Arduino should be possible with ArduBlocks. There’s a lot of thought put into the design of the blocks – the first iteration was far too ‘busy,’ but [David] cleaned it up and made the projects understandable.

For an absolute beginner, we couldn’t imagine anything better. ArduBlocks would be great for children, and we can’t wait to see a proper implementation of ArduBlocks with a touch screen.