Hedge Court Robots: Sandwich

Sandwich is a line following robot. He's the first robot I ever made (that's a small un-truth-itude, click for the truth). His body is made from a plastic sandwich container which is where his name comes from. Sandwich has photocells for sensors and an analog comparator for brains. Add in a 9V battery, a pair of DC gearhead motors and some decorative LEDs, and you've got a fun little guy who zips around the living room.

The idea, plans, and instructions for Sandwich come from Robot Building for Beginners by David Cook. I found it when a web search landed me on his web site Robot Room. Such a fantastic book, it walks you through all stages of construction of a line following robot with lots of pictures and simple language. I recommend it for any beginner, and since I'm really just a beginner myself, I'm not qualified to recommend it for more advanced folks, but I'll take David's word for it when he recommends it for all levels of reader. Check out his website, there's tons more good stuff there other than Sandwich. I can't say enough good things about the Robot Room site, I go there all the time, and in fact, I just pre-ordererd my copy of his next intermediate-level book that's due to ship in April, 2004.

As I was building my Sandwich I kept a blog journal of all my adventures. If you read some of the log you'll see that Sandwich was more than just a robot for me. I used him as an excuse to waterproof and remodel my basement, rebuild my workbench, and acquire lots of fun tools and other assorted toys. As of right now, the blog looks stupid and I haven't figured out how to customize the php templates to make it look a little more like the rest of my site. I know, I know, you think that the rest of the site also looks stupid, but at least I want them to look the same kind of stupid.

Now, on to some of the highlights of my Sandwich the Line Following Robot...

Solderless Prototype

The first part of building Sandwich is to build the circuit modules on a solderless prototype board. This is a really fun part of the process because you get to play around with the components. In the picture, you can see the power switch and indicator LED, the balanced light-sensing module, the comparator module, the two transistor-driven LED modules, and an extraneous trimpot thrown in there because I didn't want to lose it. The Robot Building for Beginners book walks you through planning, calculating, constructing, and measuring the whole circuit.

Soldering, Schmoldering

Once the prototype is functional, its time to solder some more permanent circuits together. This is definitely where my skills and the skills needed for robot making are completely unrelated to one another. You can see the pictures of my soldering iron tips that are so oxidized that they actually started melting and corroding. These tips were really inexpensive and the iron I had them in cost about $2.50. I suppose you get what you pay for because my initial experience with soldering was brutal. There's also a picture of part of the motherboard where I heated it too much and even melted a copper trace off of the board.

NOTE: I'm not trying to demonstrate proper soldering, I'm just trying to show off how horribe my technique and tools were.

Improvisation

I can only assume that there's lots of improvisation when it comes to robot building. Things don't quite line up just right, or you have "almost" the correct part lying around, or you're trying to hack a toy into something else and along the way, you've got to be ready to improvise a solution that's not in the book or datasheet or manual. My first taste of this was when my motor stopped working after I soldered the lead wires to it. Intermittently it would switch on and off. Through experimentation I noticed that if I kept pressure on the black wire pushing it out towards the outside of the motor, then the intermmitent problem dissappeared. So during soldering I must have partially melted its internal connection. I didn't want to waste $18 by throwing the motor away, so I wedged in a little piece of wooden dowel that I had laying around, and the problem was solved.

Heatshrink Tubing

Throughout the book, David Cook is continuously reinforcing how proper use of heatshrink tubing separates the newbies from the veterans. In addition to the improved physical strength of joints and protection from short circuits, the tubing gives a robot a more professional look which changes how people think of a robot overall. But does it really look professional if you use a flame to activate the tubing? I don't think so. My first attempt with a hairdryer or two failed miserably and so I used a lighter. This is literally "playing with fire" and I quickly was convinced that the $20 for a heat gun is worth the money in safety, appearance, and heat shrink quality.

Motherboard

Here's the motherboard as seen from the top. It should look quite familiar if you've also been through the book because I tried to exactly follow the suggested layout. You can see one of the yellow LEDs was not firmly pressed in place before soldering. If you look real close at the Molex KK headers, you can see the dried Liquid Nails that I had to use since I can't find silicone adhesive anywhere. The two bare wires sticking out of either side are the power bus lines that I didn't clip off yet.

Truth about Sandwich

Earlier in this page I said that Sandwich was the first robot I've ever built. At the time of this writing, 31-Jan-2004, that's not 100% true because my Sandwich is not done yet. If you look really closely at the picture in the upper right of the page, you'll notice that the body is pretty much empty. I still have to finish the motherboard and then test/tweak the full assembly. I hope this lie hasn't caused you to lose all faith in me. LIES, ALL LIES!!!!!!!
Return to the top of the page.

		Hedge Court Robots: Sandwich
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Sandwich is a line following robot. He's the first robot I ever made (that's a small un-truth-itude, click for the truth). His body is made from a plastic sandwich container which is where his name comes from. Sandwich has photocells for sensors and an analog comparator for brains. Add in a 9V battery, a pair of DC gearhead motors and some decorative LEDs, and you've got a fun little guy who zips around the living room. The idea, plans, and instructions for Sandwich come from Robot Building for Beginners by David Cook. I found it when a web search landed me on his web site Robot Room. Such a fantastic book, it walks you through all stages of construction of a line following robot with lots of pictures and simple language. I recommend it for any beginner, and since I'm really just a beginner myself, I'm not qualified to recommend it for more advanced folks, but I'll take David's word for it when he recommends it for all levels of reader. Check out his website, there's tons more good stuff there other than Sandwich. I can't say enough good things about the Robot Room site, I go there all the time, and in fact, I just pre-ordererd my copy of his next intermediate-level book that's due to ship in April, 2004. As I was building my Sandwich I kept a blog journal of all my adventures. If you read some of the log you'll see that Sandwich was more than just a robot for me. I used him as an excuse to waterproof and remodel my basement, rebuild my workbench, and acquire lots of fun tools and other assorted toys. As of right now, the blog looks stupid and I haven't figured out how to customize the php templates to make it look a little more like the rest of my site. I know, I know, you think that the rest of the site also looks stupid, but at least I want them to look the same kind of stupid. Now, on to some of the highlights of my Sandwich the Line Following Robot... Solderless Prototype The first part of building Sandwich is to build the circuit modules on a solderless prototype board. This is a really fun part of the process because you get to play around with the components. In the picture, you can see the power switch and indicator LED, the balanced light-sensing module, the comparator module, the two transistor-driven LED modules, and an extraneous trimpot thrown in there because I didn't want to lose it. The Robot Building for Beginners book walks you through planning, calculating, constructing, and measuring the whole circuit. Soldering, Schmoldering Once the prototype is functional, its time to solder some more permanent circuits together. This is definitely where my skills and the skills needed for robot making are completely unrelated to one another. You can see the pictures of my soldering iron tips that are so oxidized that they actually started melting and corroding. These tips were really inexpensive and the iron I had them in cost about $2.50. I suppose you get what you pay for because my initial experience with soldering was brutal. There's also a picture of part of the motherboard where I heated it too much and even melted a copper trace off of the board. NOTE: I'm not trying to demonstrate proper soldering, I'm just trying to show off how horribe my technique and tools were. Improvisation I can only assume that there's lots of improvisation when it comes to robot building. Things don't quite line up just right, or you have "almost" the correct part lying around, or you're trying to hack a toy into something else and along the way, you've got to be ready to improvise a solution that's not in the book or datasheet or manual. My first taste of this was when my motor stopped working after I soldered the lead wires to it. Intermittently it would switch on and off. Through experimentation I noticed that if I kept pressure on the black wire pushing it out towards the outside of the motor, then the intermmitent problem dissappeared. So during soldering I must have partially melted its internal connection. I didn't want to waste $18 by throwing the motor away, so I wedged in a little piece of wooden dowel that I had laying around, and the problem was solved. Heatshrink Tubing Throughout the book, David Cook is continuously reinforcing how proper use of heatshrink tubing separates the newbies from the veterans. In addition to the improved physical strength of joints and protection from short circuits, the tubing gives a robot a more professional look which changes how people think of a robot overall. But does it really look professional if you use a flame to activate the tubing? I don't think so. My first attempt with a hairdryer or two failed miserably and so I used a lighter. This is literally "playing with fire" and I quickly was convinced that the $20 for a heat gun is worth the money in safety, appearance, and heat shrink quality. Motherboard Here's the motherboard as seen from the top. It should look quite familiar if you've also been through the book because I tried to exactly follow the suggested layout. You can see one of the yellow LEDs was not firmly pressed in place before soldering. If you look real close at the Molex KK headers, you can see the dried Liquid Nails that I had to use since I can't find silicone adhesive anywhere. The two bare wires sticking out of either side are the power bus lines that I didn't clip off yet. Truth about Sandwich Earlier in this page I said that Sandwich was the first robot I've ever built. At the time of this writing, 31-Jan-2004, that's not 100% true because my Sandwich is not done yet. If you look really closely at the picture in the upper right of the page, you'll notice that the body is pretty much empty. I still have to finish the motherboard and then test/tweak the full assembly. I hope this lie hasn't caused you to lose all faith in me. LIES, ALL LIES!!!!!!! Return to the top of the page.