Sunday, June 6, 2010

Milling Circuit Boards

I purchased a Proxxon high-speed (20K RPM!) spindle for milling circuit boards.  After devising a way to attach the spindle to my milling machine, I used eagle (and the pcb-gcode script) to generate the G-code for the following simple board.  This board contains a microcontroller (the 8-lead device in the center), an 0805 resistor, and several pads to attach wires.
After running the g-code on the milling machine, I ended up with the following circuit board.
Then I installed some components and attached wires for power.  The micro is programmed using the 4 surface mount pads between the micro and the wires.  I wrote a program to blink out "HI" in Morse code on the LED.

Friday, May 28, 2010

Internet TV Broadcasting

For a while at TardHaus we have been experimenting with different ways of sending a live feed. We are currently testing a new setup that seems to work better than others we've tried.

Here's an example of our feed:

Watch live video from tardsat on

You may want to try it in a at the main page to compare quality:

Tuesday, May 25, 2010

Casting Apples

This apple was cast in Aluminum using a green sand mold and the "coping out" method.  The parting line was placed at the largest diameter of the apple, about 3/4 of the way up.  The flash has not been removed yet, so the parting line is clearly visible.  The images below show the detail on the top and bottom of the casting.  A real apple is also shown for comparison (not the same apple used to make the mold)

Monday, March 29, 2010

Computer Fixin's Part Deux, the Finale

Today the screen came in. It was simple to install, with the hardest part being to remember where the screws go. Because of this I tried turning it on before adding the hardware, as can be seen below.
After I got it all put together it was fine. Hooray!

For the record, I bought the screen on Ebay. The supplier was in China, and the screen came from Shenzen, China via UPS. Total time on this project was about 1 hour.

Sunday, March 14, 2010

Computer Fixin's Part Deux, Laptop Fixin's

My sister bought a Laptop recently, it is a Gateway NV7802U. Not a bad machine, it has a 2.2GHz processor, 4 GB Ram, and a 500GB. Tiger Direct review. Last week, I was told there was a problem and I said I would take a look. Below, it is in its natural state.Unfortunately, when it is powered up, it is obvious what the problem is. She stepped on it and broke the screen. I found a replacement screen for the Laptop model on ebay for $149.99 but I thought if I might open it up I could find the model of the screen. The idea was, I might find the screen directly for less money somewhere.
After some fairly difficult figuring out, I was able to pull the screen out. It was a little funny as there is a webcam in the cover just above the screen. There was also two screws in the bottom of the laptop that had to come out.

After taking it out, I turned the screen over to find the model. Voila! Here it is, a Samsung LTN173kT01-A01. You may notice that the screen (and the laptop, for that matter) was very recently made. "0935" is a date-code meaning 2009, week 35. This puts it late August of 2009.
Unfortunately, my plan hit a wall when I could only find this type of screen for more than $149.99. It turns out that the replacement for the Gateway that I found on Ebay is not this model, but instead an LG LP173WD1-TLA1 and the LG is cheaper. It looks like the LG would fit, but I am currently doing research to conform. I can imagine that Gateway manufactured this laptop (and the rest during this run) with whatever parts they could get at the moment and this screen happened to be a Samsung. At other times, they might use the LG.

Stay tuned to see if I can fix it.


Monday, March 8, 2010

Ground Loops

Last week at work, we proved that ground loops with an oscilloscope can be a bad thing. Here is a description of what happened, but the pictures mostly speak for themselves. As I understand it (I was not present) the issue occurred when a setup involving 277 volts was present. Our oscilloscope was not plugged into earth ground through the third prong, which was supposed to help look at AC signals. Unfortunately, the 'scope was plugged into the PC via the serial port (to wave capture) and then the serial ground provided at path for potential disaster. Basically, all the grounds in the circuit should be at the same point (voltage), ours were not.This picture is from the serial port on the back of the 'scope. Notice anything odd?
Same board, different angle. In this picture you can almost see the lifted traces on the board as well. That trace goes from one of the pins on the DB9 to the chip. The yellow cap. next to the chip isn't looking great either.
As it turns out, since the loop was through the PC, it was not spared either. Shockingly similar failure to the 'scope. Lucky for all of us, the hard drive was spared any damage and a duplicate PC was located to replace this lost one. The 'scope, however, could not be replaced as easily.

Thursday, March 4, 2010

Give him the Clamps!

Last September, me and Freshman were in the Barre/Montpelier area to pick up some fireworks, and we stopped at R+L Archery to check out some more fun things. When there, I saw cray fish on sale for $0.50 each (as fish bait.) So what could I do? I picked up a few and I named them all clamps. Long story short, I have one left.

Notice the food to the right, and the electrical box in the back. He calls that home. Sometimes I don't see him for days while he is hiding. The point of this post is a new development. Recently, clamps molted, why not, and when he did, he came out with one less claw. Actually, he came out with the whole arm missing. The question is, will it come back?

Saturday, February 27, 2010

Sno' Movin'

We got some snow... 20+ inches... and then it changed to rain. The driveway was turning to slush, and the snow-blower was having trouble with the heavy wet snow. This, of course, means it's time to break out the big snow machine. Bill and Ollie got the battery hooked up and fired it up. The 3-53 runs like a champ!

Then we had to clean a path through the back yard so we could get the bucketloader into the parking lot.

By taking successive swipes with the bucket, we got the parking lot cleaned up to an acceptable level. We were worried that if the slush froze, it would leave 1 foot deep ruts in ice, making it difficult to get out of the parking lot. Here, we're just removing a lot of the slush and making a big pile across the road on the far side.

While the machine was out, we moved some snow around and made some little jumps in the backyard, which Ollie immediately took advantage of.

Sunday, February 14, 2010

Computer Fixin's

Here is a sad G5 iMac. It is so sad that it can't even make the frowny-mac face. When you try to power it up, it doesn't do anything. Careful listening reveals that it starts to power up but then powers down within 1 second.

This, of course, means it's time to take it apart. As suspected (because of its age), some of the electrolytic capacitors in the power supply section had failed. These things typically only have a 1000-2000 hour lifetime, so it's not uncommon to see failures in older electronics. A quick order to DigiKey (about $20 worth of parts), a bit of soldering to remove the old caps and install the new caps, and it was ready to put back together. The knife block in the picture was used to lean the motherboard against so I could heat the solder on one side and pull the cap off from the other side.

Yay! A happy mac! It's very satisfying to fix broken electronics.