Archive for the ‘Robot’ Category


Thursday, June 4th, 2009

I bought a Solarbotics “mousebot” a few months ago.  It’s kind of cute:

overhead view of mousebot

The mousebot’s official name is Herbie, which seems to have become a “cute” name in the last 40 years or so, possibly having something to do with the eponymous(e) Volkswagen.  Let’s look at another view of it:

close view of mousebot

Less cute.

mousebot kit

The kit’s instruction book is pretty well thought out, being large, well-illustrated, and detailed.  It is evident that the target market is new hobbyists, as there is a goodly amount of explanatory text, cautions where appropriate, and a scattering of jokes appropriate to the younger set.  This is fortunate, since one goal of my assembling the kit was to get comfortable with soldering.   (If this article reads slowly, it is because I am now typing with a bandage on my finger.  Fortunately, I only burned myself once.)

The kit, once assembled, proved to be quite durable, which impression I tested by accidentally stepping on the bot shortly after completing it.  The shell, held together by numerous solder joints, stayed intact, and the only damage was the motors breaking their moorings.  Fortunately, despite other shortcomings, I possess a solder sucker, which made short work of the (now bad) motor wire connections.

Assembly is straightforward, with one major caveat. The problem is that the battery fits quite tightly, so tightly that it is possible to construct the robot in such a way as to result in a too-small battery compartment.  I had to solder the LM386 chip directly to the circuit board, rather than using the socket provided.  This gave me a bit more room, and I would also suggest fitting the motors with the battery installed.  I would not suggest this kit for anyone younger than, say, 12, given the necessity to think around this problem.  Without a solder sucker, a razor blade, and some patience, I would have been out of luck.

underside view of mousebot

Being unable to leave anything stock, I did make one modification.  After the above picture was taken, I bound the front “whiskers” together at the bend just outside of the circuit board.  This made the whisker assembly a bit stiffer.

So, what does the robot do?

It is an example of the “light-seeking” type, sometimes called a “photovore”.  This sort of robot is a popular choice for inexpensive introductory kits, since the infrared sensors (the eyes) are cheap, and the robot can be led around with a flashlight.  Unlike most such kits, which are solar-powered, Herbie instead uses a 9-volt for it’s energy source, making it very fast for such a little kit with no gearing.  It moves at a brisk walking speed, and will likely outrun your kids.  Given that it has no suspension, it is best suited to very flat flooring; it would do well on a table but for a propensity to do a header over the edge after .5 sec running time.

The whiskers and the tail are both impact sensors.  When it flexes far enough, each sensor bumps the conductive ring surrounding its base, engaging a backup circuit that tells the robot to back up for a moment, skewing its direction a bit.

As is usual for me, the assembly of the kit is more fun than playing with the result, but given its purpose as a learning kit, this is perfectly OK.  The kit is a few dollars more expensive than I would prefer ($40 or so), but one is paying for the very good instructions as well as the parts, and so I don’t think the cost unreasonable.

mousetrap and robot

(Lest you worry, I know that cheese is bad for mice, but Herbie can’t be hurt by the past-its-sell-date Rambol in the trap, nor, really, the trap itself.)