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Miniature Rotary Stewart Platform Demo

I made a Stewart platform like this several years ago and used aluminum parts that cost a small fortune. I had it stuck in my head that no one would ever want one because it was too expensive. Recently I was contacted through my website by someone who found my old machine at Let’s Make Robots and wanted to buy one. It’s like a light going off in my head when I realize “Hey, this is actually affordable now!”

Long story short: I’m going to work on the printed parts a bit more over the next two weeks and then get this into the store for anyone interested. The code will go up on GitHub. Can we get it to work with GCODE like most of the other machines? I think so.

Stewart platforms are used in flight simulators, driving simulators, robotic surgery, and even docking shuttles to the international space station.

Here’s an idea: Stewart platform + GPS + clock + telescope = DIY star tracking. Just putting that out there.

The most challenging part of assembling this kit is cutting the rods in half. Just FYI.

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HOG Drive Line Following with QRD1114 Sensors

You can find more great stuff like this @ www.marginallyclever.com.

I’m using QRD1114 Infrared sensors to control the movement of a Hemispherical Omnidirectional Gimballed (HOG) Drive for a line riding robot.

I’ll probably mount five of them in a row so I can expand the code and make a maze-solving robot. This thing is fast enough that I’m also going to need a PID controller in the software.

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QRD1114 Circuit How-to Tutorial (or “Where did I put my brain?”)

My line following/maze-solving robot has been bust for too damn long. I just spent two weeks staring at this circuit, unable to figure out why it doesn’t work. Can you see it?

Neither could I, at first. I thought maybe the QRD1114s had been assembled backwards, but that couldn’t be right, could it? It wasn’t until I took a break and restarted from square 1 that I spotted the error, which – I’m sorry – is not in this photo. I the + and – lines connected to the breadboard were reversed, I was running power the wrong way through the circuit. When I looked at the board I saw what you see in that picture. The wires were right there in my peripheral and I missed them completely.

There’s a lesson in every mistake. What is the lesson here? Double check everything? I thought I had. Reconfirm your assumptions? That’s improbable going on impossible. I wonder how many times I will have to wire things backwards before I learn to check it every time. How many times do you have to experience a lesson before you learn and pass the class?

Below is how to wire the correct circuit. I’m using 1k resistors for the sensor and 220Ohm resistors for the IR LEDs. The dot on the top of the sensor is next to pin 1. pin 1 and pin 3 are 0.050″ longer so you know they’re the positive legs.

Here’s a single sensor in the array, isolated for simplicity.

Here’s the sample code I ran on the Arduino.

[code lang=”c”]void setup() {
Serial.begin(57600);
Serial.println(F("Hello, World!"));
}

void loop() {
Serial.print(F("0=")); Serial.print(analogRead(0)); Serial.print(‘\t’);
Serial.print(F("2=")); Serial.print(analogRead(2)); Serial.print(‘\t’);
Serial.print(F("4=")); Serial.print(analogRead(4)); Serial.print(‘\n’);
delay(100);
}[/code]

Here it is working in a robot.

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EL Wire Blowout Sale Until 2013-04-14

I’ve got a lot of EL wire and it’s time I get rid of it to make room for more robot stuff.  From now until April 14, 2013 I’m offering all 5m EL Wire at 17% off.  Every kit includes a driver. All you have to add are two AA batteries.  Perfect for decorating your bike or your person.  If you come up with something creative, let us know!  We love to share pictures.  When they’re gone, they’re gone – I’m probably not going to restock them in the near future.

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MediaWiki for Internal Process Control

Every mistake is a lesson in disguise. Recently I’ve noticed:

• My memory, already bad, is getting worse.
• My number of steps in each task is growing, as are the number of tasks.
• My desire to operate flawlessly and keep everyone happy is extremely high.
• My desire to teach someone else how to do every little step of business process is crazy low to non-existent.

These things are in conflict with each other. My solution has been to write down every step of a task that repeats. Now I don’t have to try and hold it all in my head. When I need to do a job, I look it up. If I can’t find it, I create a new list.

…which works fine if there’s two or three lists. I quickly realized I was going to need a LOT more lists. Writing it on paper was crash-proof (yay) and hard to edit (boo). Solution? A MediaWiki set up on the LAN is now going to serve up all the documents office-wide. MediaWiki is the same software used for Wikipedia, so I know it’s been well tested.

I hope with this I’ll be able to refine my process and build a kind of “Choose your own adventure” for new employees.  Need to know how to do something?  Look it up!

The next big challenge will be predicting when I need to order parts so that they arrive just before I run out of that part.  I couldn’t do that before I started ordering and making sales but as the data builds up I should be able to plan ahead very nicely.  I’m not even going to bother looking for an open source solution – to work right it’s got to be completely integrated into my store.  I don’t want to have to copy data back and forth, I just want a notice saying “it’s time to order [number] units more of [part x]”.

Do you have a favorite way to stay organized? Share! It pleases my OCD.