LEGO Safe

After Duncan and I had really gotten into the LEGO Mindstorms a couple of weekends ago, we were looking for an exciting new project to build.

Duncan had seen a LEGO Safe on one of the videos that comes with the Mindstorms v2.0 CDROM and wanted to build it. It was in the Pro Challenges section. There were a set of snapshots and "3D" views for how to build it. Apparently they are seriously about the Pro part here. I reckon only people who have previously been employed to build the models at the LEGO theme parks are going to understand these. Or kids who spend every waking moment playing with LEGO. I couldn't make hide nor hair of them. At least not enough to want to keep trying.

We gave up that particular project that day after a couple of hours, and went onto something else. Over the next few days, I looked around to see if there was anything that could have helped me. What I was really looking for, was a set of step-by-step instructions -- like that ones in the Mindstorms Constructopedia -- that we could follow in order to build the safe.

What I did find was that there was book 10 Cool LEGO Mindstorms Robotics Invention System 2 Projects and that one of the "robots" was a LEGO Safe. Cool indeed. I found a used copy for sale on Amazon for 5 bucks and ordered it. It arrived last week. I quickly scanned it. It did have step by step instructions for each project and one of the projects was a safe. We were set.

This last weekend, we started building our safe. It says that each project should take an hour. Yeah right. For the authors maybe (or those ex-employees at LEGOland). The pictures unfortunately do several building steps per picture. The fuzzy gray black and white pictures are not crispy clear. It's difficult to see where one brick starts and another ends. Have you ever taken something apart and when you put it back together you had several pieces left over? We had the LEGO equivalent of that. Each picture comes with a list of the parts you are going to use in this step. Quite often we had some left over and we couldn't work out where they were supposed to go.

(Note that it looks like the quality of the instructions for different robots within the book varies quite a bit. The instructions for the F1 Racer look much better.)

For a couple of stages, we really struggled. Working out exactly how the motor with the extended shaft fitted through the side to drive the gear that opened and closed the safe door was one of them. Still, if you treat it like a puzzle and don't get too frustrated you will eventually get there. At least there is now a fuzzy color picture above that might help others. The green bricks above are a Duncan extra. If you didn't have them, the safe would have a big hole. A hint that perhaps we still didn't build it correctly in the end.

I then had to go to the publishers web site associated with the book, register, then enter a special code (given in the book) in order to download the program that would operate the safe. This really seemed overkill. I've no idea why they couldn't have made this easier.

Debugging the program was the next challenge. I literally had to take it apart and test each section separately. We had got the orientation of the leads for the touch sensors incorrect so they failed miserably with the safe door continually opening and closing. The pictures in the book are very confusing. After that I had to change the light sensor code to look for a certain level of darkness not brightness. We got there in the end though.

After that, I wrote my own little program from scratch. One touch sensor would open the safe door. The other would close it. Each operation played a different note. This impressed Duncan much more that having to hit the left sensor four times and the right one three times in order to open the safe (their original program).

Before we start the next project, I'm going to do a bit of prep. work. I'm going to try to fully understand the building instructions and the downloadable program in advance to keep the project rolling along and keep down Duncan's frustration level. Don't get me wrong, I like the book, but it could have been so much better. Clearer instructions. LeoCAD files for each project on the publishers web site would have really impressed me. It also assumes a certain level of LEGO Mindstorms expertise that, (because I'm not doing this all the time,) I haven't achieved yet.

Maybe they will come out with a new edition that addresses these problems.

Maybe there is somewhere on the web that has a better LEGO Safe.

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( Dec 12 2005, 07:15:38 AM PST ) [Listen] Permalink