(Back ball bearing assembly, with multiple-height standoffs. I used the tallest of the ones available. You put the ball bearing inside the cone piece, and put the cover on that. Pick the standoff you want to use, and mount everything on the universal plate.)
A few weeks ago, I was in the Junkudo bookstore, about 1 mile from my apartment, looking in the electronics section. Junkudo has a number of actual parts kits in with the books, and one of the kits is an old magazine+box for a small 2-motor robot educational kit. $130 ($140 including tax). Since Gakken hasn’t come out with anything new in close to a year, and there hadn’t been any sign of anything on the horizon, I decided that I’d get this robot and see if I could get it to work.
There are two main body design styles: The box, and the L-panel stubby. The box is fine for playing soccer or line tracing. The stubby is about half as long, and is better for obstacle courses that include ramps. They’re both the same robots, electronically. It’s just that the hardware for the frames are different. I chose to build the box (if you use shorter side rails, the robot isn’t as tall, and it ends up looking more like a sandwich). I didn’t see recommended assembly times in the book. I took 3 hours, mainly because I had so much trouble with the hex nuts. The kit comes with two small plastic Phillips head screwdrivers, and two hex nut wrenches. The screwdrivers are useless for anything but holding the hex nuts in place for the side rails. Generally, I had to resort to my regular driver set.
The parts are all packaged in clearly identified plastic bags, with sheets of paper inserted that have the descriptions and parts lists in English. There’s lots of extra nuts and bolts of various lengths, for customizing the robot as you like. So, that part is really well-done.
The book is broken up into several chapters. The first has the parts lists, and photos so you can check if anything is missing. followed by the assembly instructions for the motor plate, and then the instructions for both the Box and Stubby body types. The second chapter discusses the robot programming environment and how to download programs to the kit. The third sections on up cover different programs, such as the line follower, obstruction avoidance, and the soccer player.
Although it was really fiddly putting the kit together, it is pretty solid, so I don’t have any complaints about that. In general, you can put everything together with just a good screwdriver and the hex nut holders. What I don’t like are: Having to solder the infrared LEDs, and needing to use a 9-pin serial cable to interface the kit to a PC.
(To mount the electronics, you pick the body type first – either the L-plate, or the second flat plate. I used the flat plate. Then, you tighten down the hex nuts on the 3/8″ bolts to act as stand-offs. After that, you just put the boards on the bolts, and hold them in place with another set of nuts. Shown here are the controller-motor drivers, and the RS-232 interface board.)
If you want to make a line follower robot, you need to use the 2 infra-red boards. For those, the photo transistors are already mounted on the top of the circuit board. However, the IR source LEDs are supplied individually, and you have to solder those on yourself. There’s nothing on the outside packaging on the box saying you need a soldering iron and solder. I have both of those, but the one electronics shop in my city just went out of business at the end of September, so the only way I’d be able to get an iron at this point would be to mail order one. Sigh. Even so, it’s a pain having to find the box the iron and solder are in, just to tack down a total of four leads. (Which I haven’t done yet, as of this writing.)
The more serious concern is that the kit software running on the PC communicates to the RS-232 interface through a 9-pin serial cable. My laptop doesn’t have a 9-pin port. None of the laptops I have looked at so far have 9-pin ports. Bic Camera doesn’t carry a 9-pin to USB converter cable. The electronics store near me is no longer in business so I don’t know if they had a converter cable, either. Worst case, I may have to order one from the U.S., and hope that it works with the kit. Sigh. If not, then I just spent $140 and 3 hours on a paperweight.
(Finished Box type chassis, with most of the cables attached. The controller is off-the-shelf, and is capable of driving up to at least 4 motors, and handling other sensors. There’s no schematic for it, so I don’t know what all the connectors are for. I haven’t soldered the IR LEDs onto the IR sensor boards yet, so those haven’t been mounted on the front bumper. I’ll do that later.)
Still, for a paperweight, it does look impressive. Again, if I replaced the side rails with shorter stand-offs, the robot will look more like a sandwich.
And, this is the last of my backlogged posts for this blog. I don’t have any other science or math-y things to write about, no other books to review, or Gakken kits to build (until late December). So, I guess this blog will go on hiatus again until I find something new, or until after Christmas.