Safety First! Switching 120vac loads with a microcontroller

Rob writes in… [via]

I’ve seen quite a few hacks related to controlling appliances, lights, etc over the years and just wanted to share a little info so that everyone has access to a cheap way to do it relatively safely. By trade I work in the building controls/integration industry and as a result I use these relays at work and at home(chicken coop control,light,etc)quite a bit.

The interface between your microcontroller of choice and the relay is a simple 555 relay driver circuit. I have included the pdf that inspired me to do it this way. The relay I use is the RIBTU1C. The reason I prefer this relay is that the coil will run on 9VC @ 20mA and the contacts will switch 10A @ 120VAC. Total cost for the RIB and a 555 is under $15 if you shop around. In addition the RIB has a partition inside the box between the line and control sides. There’s also room for a Radio Shack breadboard in there!

Safety First! Switching 120vac loads with a microcontroller – [Link]


Portable, high-res 3D imaging tech

Portable, high-res 3D imaging tech

MIT researchers have improved a gel technology that can image microscopic features without expensive equipment, opening up applications in forensics, medicine, and other fields.

Developed by Edward Adelson, Micah Johnson, and colleagues, GelSight acquires surface textures and shapes by pressing a block of clear rubber onto them, revealing striking 3D details. It can even visualize a pulse when pressed on a wrist.

Originally presented in 2009, the technology has been improved to resolve features as small as 2 microns across and is being presented in a paper (PDF) at this week’s Siggraph 2011 computer graphics conference in Vancouver, British Columbia.

When an object is pressed against the clear rubber, its reflective skin on one side distorts to assume the shape of the object. The skin is coated with paint that contains flecks of metal that are smaller than the features they resolve.

Portable, high-res 3D imaging tech – [Link]


Building a simple Fritzing component

HOW TO – Building a simple Fritzing component… Bertrand writes – [via]

This is me shaving a yak. Shaving the yak, if you don’t know, is what you do when a seemingly simple task necessitates many recursive and unforeseen sub-tasks in order to be carried out.

The story goes like this… Let’s say that I want to paint a picture, but I’m in a shack in the middle of the desert and I don’t have a canvas, brushes or paint. I do have a piece of strong cloth, a few pieces of wood, and the rocks around the shack can provide some pigments that I can mix with some oil. For the nails, I can extract some from the shack’s structure itself. For the brush, I’ll need some quality hair. Well, long story short, before I know it, here I am, in the middle of the desert, shaving a yak.

Today’s metaphorical yak is the representation in Fritzing of a $0.95 part, a knob potentiometer. Fritzing is a wonderful Open Source tool for designing electronic circuits. Its only shortcoming is that its library of components is not yet complete enough that it can be used to design all circuits. In my case, it’s lacking the SD card reader that I’m using, analog sticks and… this small $0.95 potentiometer. Well, in fact, for the potentiometer, I could have easily used one of the stock components from Fritzing that is close enough, but for my first component design, I wanted to start with a fairly simple part so I went ahead with it anyways, with the hope of having a better fit in the end.

Building a simple Fritzing component – [Link]

Using VFD display with Arduino

Using VFD display with Arduino – [via]

Summer of 2010 I picked up an Arduino board from adafruit and took some time to walk through all of the tutorials available with it. Since then I have spent most of my time on other projects including my bachelor’s. Recently I have obtained the Motor Party Pack, LoL Shield Kit, and a 20×2 VFD (Vacuum Fluorescent Display) to go with the original board so my interest is sparked again. I have found that the Motor Party Pack and LoL Shield have adequate instruction and tutorials, but the VFD is lacking in beginner level instructions to get started. As such I have decided to write a tutorial for the 20×2 VFD available through adafruit.

The adafruit VFD is made by Samsung and is model No. 20T202DA2JA, this is really unimportant though as adafruit is nice enough to link you to the spec sheets for both the module and the controller chip. What you would be looking for is the pin-out found on page 4 of the module controller sheet.

Using VFD display with Arduino – [Link]

VT220 serial console (circa 1983) set up as a terminal for Mac Pro (2010)

VT220 serial console (circa 1983) set up as a terminal for Mac Pro (2010) – [via]

My biggest source of information getting this going was Paul Weinstein’s post about setting up an Apple IIc as a terminal for his Mac mini (which is similar, but not quite the same since the IIc still has to emulate the terminal in software). I got the same USB-to-serial adapter, a Keyspan USA-19HS ($27), which has Mac drivers that I can happily confirm work well with 10.7 Lion. I also needed a null modem cable ($7) and 25-pin female/female converter ($4) to connect it to my VT220.

At first I used the same method as Paul to get it working, gluing together the terminal and OS with a utility called screen. As Paul notes, this is less than desirable. It still requires you to open a software terminal to make the connection, and you’re still operating through a layer of emulation. On most Unixes you can simply add a line to /etc/ttys and everything just works via getty, but apparently this has been disabled in OS X since 10.5.

Eventually I found this page, which explains the problem and how to fix it. After adding a line in /etc/gettytab to manually set the terminal type to vt220-8bit everything works perfectly! A real hardware terminal directly connected the old fashioned way, with no emulation. Awesome

VT220 serial console (circa 1983) set up as a terminal for Mac Pro (2010) – [Link]


Sharp "Memory LCD"

Check out this Sharp “Memory LCD”

Memory LCD Technology
Display technology advances such as LED backlighting have dramatically changed the game of LCD power consumption. However, the power requirements of some conventional LCDs can still be high enough to limit their usage pattern or usage environment.

The industry’s first incarnation of memory LCD technology yielded cholesteric, electrophoretic, and other bi-stable technologies. However, these types of displays require relatively high driving voltages and considerable time to respond, in some cases requiring most of a second to update display images. They are also extremely limited in the amount of content they can display at one time.

Electrophoretic displays have also been known to experience image retention. Some current display technologies eliminate this possibility by designing a display to update twice. The first update is with a negative image to completely switch states in the display, and the second update is with the new positive image. Thus, the true update (or “refresh”) rate in a typical application of this type may actually be twice that which is stated in its specifications. Due to this, even though electrophoretic displays do deliver energy savings when holding state, power drain during image updates is a real concern. (more…)

Sharp's "World's Most Efficient LED Ceiling Light"

Sharp’s “World’s Most Efficient LED Ceiling Light”. A little pricey to start, but that’s how it goes… [via]

Sharp’s “‪World’s Most Efficient LED Ceiling Light” – [Link]