HACK A WEEK

In Februrary of 1880, Alexander Graham Bell and his assistant Charles Sumner Tainter invented a device that allowed the transmission of sound via a beam of light. It was called the Photophone. Bell believed the Photophone was his most important invention! Indeed, 100 years later in the 1980s fiber optics came into widespread use. It is noted on a plaque that on June 3rd, 1880 the first wireless transmission of a telephone message using the Photophone took place. This year marks the 131st anniversary of this event.

Bell’s Photophone used crystalline selenium cells at the focal point of its parabolic receiver. My version uses a solar cell as the receiver. The transmitter is a mirror attached to a speaker aimed at the solar cell. The mirror is aligned so that it reflects the Suns rays onto the solar cell. The solar cell is mounted at one end of a black 4″ ABS pipe about 2 feet long. The light reflecting off the mirror is modulated by the vibrating speaker. The Solar cell receives this modulated wave of light and outputs a corresponding modulated voltage that can be fed into an amplifier and output through a speaker to produce audio. A 0.1 uF capacitor is connected in series between the solar panel and the amp.

The whole project is quite simple and fun to build. Enjoy the video and.. as always, Keep On Hackin!

This week I built small single coil guitar pickup to demonstrate the way they work by induction. This was a really fun project because I ended up also building a simple one string guitar! There’s a lot of info on the internet about building your own pickups. This one is very easy to build with common parts. All that you need is a magnet and some magnet wire!

A guitar pickup is a simple inductor. At it’s center is a magnet and around it are windings of copper “magnet wire”. Magnet wire is simply copper wire with an enamel coating which serves as an insulator. The pickup is mounted under the steel guitar string so that when the string vibrates, it alters the magnetic flux thus creating a voltage.

A pickup is essentially a generator or dynamo. A generator is defined as “The production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic flux”. The copper wire serves as the conductor with the change in flux generated by the wire vibrating in proximity to the coil.

A pickup has an inductance measured in “Henries”. One henry is the amount of inductance that is required to generate one volt of induced voltage when the current is changing at the rate of one ampere per second. Two other characteristics of a pickups are a resistance measured in ohms and a “distributed” capacitance which is in parallel with the inductance of the coil.

The combination of these three factors – an electrical circuit comprising an inductor and a capacitor connected in parallel, with a resistor in series – is effectively a tuned circuit with a well defined resonant frequency. Most pickups exhibit a peak frequency between 2K and 8K depending on the type.

These are really fun to build so I encourage you to give it a go and experiment!

Keep on hackin…. 🙂

Inspired by my friends at Toymaker Television, I decided to build an interactive Cat toy thingy. After some thought, I figured that a toy mouse poking it’s head out of a hole might be fun. When the Cat whacked at the mouse, it would disappear inside the hole and then another mouse would pop out of a nearby hole! This could be lots of fun for a Cat!

So, then I thought about how to make all this happen. At first, I thought about using a micro controller and some sensors, but no, as usual I wanted it to be simple. After some more thought I realized that I could do it all with a few switches and a pivoting lever, and so, I got started making a plan. Now, when I plan something. I literally sleep on it. Things just come to me in my sleep, or I’ll wake up with a solution to a problem. That’s how this project got designed… I slept on it for a few days.

After I had a solid idea in mind, I sat down with pen and paper and a few drafting tools like a divider, a ruler, a circle template and a pencil. I drew out a design, then made a working 2D model of the mechanism. Once I worked out all the details, I built the heart of this device, the central lever that holds the two mice and functions as an actuator for several switches. I decided to use an RC servo to do the work so I opened one up and modded it to free rotate past 180 degrees, and wired it direct to the motor, Basically, I turned it into a gear reduction motor.

Then it was time to put it all together, which took about 10 hours over two sessions at the bench! A lot more time than I would have estimated, but there were several problems that came up that had to be solved. That’s what rapid prototyping is about. Solving problems quickly. Along the way I made a few changes and additions.

Finally, I had a working device. Time to let the Cat, Seamus, have at it….

Talk about an anti-climax! He was not only disinterested in it, he was a bit freaked out by it and didn’t want to be near it! What the hell? Mouse filled with Cat Nip… interactivity… nope. Seamus would rather just go sleep. Ahh Kittehs!

Not to be let down, I let Sophie the Dog have a go at it. She was pretty excited about the ball launchers so why not! Well, she loved it! As you’ll see in the video, sometimes projects end up working differently than you had planned, or even thought of. It’s not a failure… it’s a surprise and a realization that your project has more applications that you had originally thought of, or conceived. Bonus!

I’ve always admired the film maker Ken Burns. His use of still photos is a trademark called “The Ken Burs Effect”. They’re brought to life through the use closeup shots and slow pans.

I thought this technique would be a good choice in producing a video memorial for my Mom on Mothers Day. She passed on two years ago and I wanted to pay a tribute to her with pictures from her life. She was very influential in my childhood as someone that demonstrated the DIY spirit in her daily activities. She sewed clothes for us, baked bread, tended a garden, canned goods for winter, knitted mittens and hats for the needy, made quilts, grew wonderful flowers and cooked simple nutritious meals for us every day.

I knew that the dolly I wanted to build had to move freely in two directions. After some thought, I realized that this old broken flatbed scanner/printer I had was a good choice for parts. The ink cartridge holder and carriage would take of holding the camera and allowing free movement in left and right directions. I could add some rollers to the end of this carriage so that they could rest in a drawer slide and allow movement fore and aft. Another bonus from the scanner was the glass flatbed. I could flip it over, place my photo under the glass and it would be held flat ready to reproduce on video or still digital photo. Perfect!

As a side note, YES… I realize there is software out there that will do this for me however I like to build stuff so, to quote Frank Sinatra, “I did it my way!”

I first stripped the carriage down to the bare essentials, mounted the rollers and camera mount then set to work on the frame. A few pieces of wood served to build the frame and legs to which I added two salvaged drawer slides. Then it was simply a matter of placing the dolly over the flatbed, lighting the area with a bright light and I was ready to shoot!

This is a good example of re-purposing existing hardware into something new. I do a lot of this. Yard sales and thrift stores are great places to find these items, usually quite cheap. In the videos below you’ll get to see a step by step build of this project and the video I made using the dolly. It was pretty emotion filled video session looking at all these photos of my Mom. Of course, I miss her. She was a wonderful Mother and so I say “Thanks Mom” with this tribute to her life.

Enjoy watching and keep on hackin!
Dino

This week I decided to share a repair I did on a Dell Mini 10v. I got it on ebay for a very reasonable price because it had a broken USB port, It appears it got dropped with a device plugged into the port, and it broke the port. This is a fairly common accident. First I had to come up with a replacement port. Since I didn’t have any dead computers in the “bone pile” I went to my local “dollar store” and checked out the cell phone accessories. They always have cheap stuff and I got lucky and found a 12 volt charger that plugs into a cigarette lighter socket and has a USB port with 5 volts output for charging and powering USB devices. I bought it for $5 and brought it home where I promptly took it apart and salvaged the USB port from it to use in the Dell.

Next I had to get inside the Dell Mini. When you first look at it, it seems pretty difficult to get inside but, like most laptops and net books, it isn’t that hard. On most laptops, you gain access to the motherboard by removing the keyboard. The keyboard can be held in place with screws from the bottom or some simple release clips at the edges. The Dell Mini has 8 screws on the back, three of which hold the keyboard in place. The other five hold the top cover on. Up top there are three more screws to remove along with the hard drive and then the top cover comes off

Once inside you can remove the connectors to the motherboard and take it out, replace the hard drive, upgrade the RAM and make repairs as needed.

Follow along on with me on the video and you’ll learn how to get inside the Dell Mini. If you apply this approach to other laptops and net books you’ll soon learn that it isn’t that hard to figure out how to get inside these devices and repair them yourself!
Happy hackin!