Archive for July, 2009

Arduino Offset Header

Thursday, July 16th, 2009

The Arduino has a problem.
Not a big problem by any means, but still annoying under certain circumstances. As the story goes, an 11th hour design mistake has left the Arduino community with a header that doesn’t follow standard 0.1″ (2.54mm) spacing.

So what?


For the most part, this flaw is completely transparent to the user.  Either they plug wires directly into the header, or use shields that have been designed to mate nicely with it. The problem occurs when trying to create your own shield. When you try to line up a standard perfboard with the Arduino, the header doesn’t match up. This has left the community either buying protoshields or resorting to various other DIY techniques. (here’s two.)

An Easier Solution

Offset Header
offset header - standard shield
Thanks to my hackerspace, I’ve been able to machine a jig to make Offset Headers. In my opinion it’s a great solution to the problem. Slide one through the perfboard (or whatever other 0.1″ spaced board you’re using,) solder in place, and you have an Arduino-spaced shield using a standard-spaced board.

But wait… There’s more

offset header - arduino shield

So that takes care of the cheap-shield issue, but there’s more that this header can do. There are TONS of Arduino-spaced sheilds out there. In my opinion, that’s one of the main things keeping people from developing and buying standard-spaced Arduino clones. Currently, if you make your clone standard-spaced, you’re going to alienate all the existing Arduino shields.  Having these offset headers lets users buy a clone without fear of shield compatibility.


Many Headers

So that’s it. Offset headers by the boatload.  Hopefully someone somewhere finds them useful. I’ve sent a preliminary batch over to Adafruit, so they should be available there shortly. 

(UPDATE:  they are now available here)
(UPDATE: SparkFun has them now too.)

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PID Front-End v0.2

Saturday, July 4th, 2009


Some people spend the 4th of July relaxing with friends, drinking beer, enjoying some good weather. I… updated the pid front-end. I got several requests to add grid lines and axes, and now was the time. For those of you with an image of me in a dank basement coding away, fear not. There was a Hawaiian shirt and a hammock involved.

The picture says it all. The trend lines are a little thicker, and there are now axis labels and grid lines. It’s also worth noting, since it was a pain to code, that the time gridlines and labels scroll, and can be displayed in milliseconds, seconds or minutes.

It can be downloaded here.

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Holy Crap I Made Cheese

Thursday, July 2nd, 2009


That’s right. Cheese. I was surprised by how easy it was.  It was just a simple farmer’s cheese, but still.  Making cheese is one of those things you just assume is impossible; for professionals only.  Turns out people have been making it for a long time, with tools far cruder than what we have today.  Who knew?

This could probably be an Instructable, but I’m not an expert, and I’d hate to inadvertently lead someone astray.  This is what worked for me, your results may vary.

So let’s get down to it.  I used this recipe / procedure.  Other than grossly over-specifying the amount of salt needed, it was easy to follow and gave good results.

Step 1: Heat the Milk


The recipe says something like “Slowly heat” until “about 180,” stirring “often.” I approached these statements with the meticulousness of an engineer doing something for the first time. First of all… ABOUT 180? No way. Digital thermometer. As far as slowly, I put the stove on low, and got a heat rate of 5-10 degrees/min. I rounded out the overkill trio by deciding to stir every 20 degrees. I’ve since made cheese again, have been more lax, and it still came out fine. (I still use the thermometer though.)

Step 2: Curdle the Milk


Once the milk was at temperature, buttermilk and vinegar were added. Lowering the pH of the system causes the solids in the milk to want to separate. I think. This will happen at any temperature, but it’s amazing how quickly it starts when you’re at 180 degrees.

Step 3: Strain

cheese clothdrain1

After about 10 minutes, it’s assumed that all the solids that are going to curdle have curdled. Time to get them out of there! Using cheese cloth and a strainer (for support,) I was able to keep the curds and dump the whey. Yes. Curds and whey. This is where that comes from. Why Miss Muffet would want to eat whey is beyond me. The curds are tasty though.

Step 4: ENJOY


The last step is to salt to taste. I used 1/4 tsp. That’s it. Serve in the recipe of your choice. In the picture above it’s mixed with tomato, olive oil and basil. Delicious. It also works really well in mashed potatoes. The cheese apparently lasts for 5 days in the fridge, but it’s been gone after two days both the times that I’ve made it. 

I can’t stress how easy this was.  While it takes around 1:30 from start to finish, more than an hour of that is time where you can do something else.  Totally worth it! 

The next step for me is to make “real” cheese.  That means renet, and aging. At least I think that’s what it means.

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