Home  Sources  Part descriptions Assembly descriptions  Motor drivers  Sensors  Contact Sensors  Proximity Sensors  Sound Sensors  Field Sensors  Light Sensors  State sensors  Solar engines   BEAM Pieces is a BEAM Reference Library site.		Contact sensors Making contact Contact sensors (as their name implies) require physical contact with some other object in order to "trigger." While this is sometimes a bit inconvenient for your 'bot (unlike proximity sensors, contact sensors won't help a 'bot avoid an obstacle before it is within "arm's reach"), it has two big advantages: Contact sensors are very easy to build at home from various bits & pieces you probably already have lying around. Contact sensors don't draw power until contact is made.   Obstacle avoidance contact sensors Contact sensors for obstacle avoidance are essentially the electronic version of a cat's "whiskers." In most designs, a whisker is attached to one electrical contact, and this contact gets pushed into another one if the whisker touches something. You can also just mount a "whisker" to a small pushbutton switch (you can salvage some nice "soft" ones from floppy drives). Ian Bernstein's site has an excellent tutorial for one contact sensor design here.   Ground contact sensors Some BEAMbots may want to know when a leg touches the ground. Here, you'll need some sort of a foot contact sensor. Again, you can use a "soft" pushbutton switch (preferably salvaged) for this job. You can also build a fairly simple ground contact sensor of your own. Clifford Boerema, Jr. posted a nice design for a foot contact sensor. I drew up a similar design for a normally-open sensor, using a spent .22 cal cartridge (if you're a "plinker," you should be able to come up with lots of these). It's normally-closed cousin is here.
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