Robotics

Droidmakr (Cliff Boerema) came up with an interesting idea for a light-tracking head with a form of peripheral vision. As often happens, the circuit turned into something different -- a photopopper:

All done with a single 74HC14 (the '240 being a motor driver).

I tried the same setup with the 74*240 (with an extra inverter per motor) and 7404, but the 74HC14 seems to work best.

I wanted to share an adaptation of the Schead v4, that I have been experimenting with. It is (for lack of a better term) a Master/Slave Schmitt Comparitor Head (M/S SC-H). With the addition of a 74 AC 240 or two (as motor drivers) and a pair of motors, you can put together an interesting little light seeking, wheeled robot with peripheral vision.

As long as the light reaching the photo-bridge of the Master SC-H is balanced, then the Slave SC-H acts as a regular, lone SC-H would. So, if one of the slave photo-diodes detects more light then the other, the inverter that controls the motor on that side changes states and is now the same as the inverter of the Master SC-H tied to the same motor. This turns that motor off and the robot will pivot around the stopped wheel toward the greater light source until the light on each sensors is balanced and the motor again begins to turn.

I am also using SCar to continue experimenting with Stacking separate Sensor/Behavior circuits onto a robot. I will post more as progress is made.

These bots are powered by a Gold Cap and for a period of about one minute they move, always looking for the brightest lightspot, so in fact they will even follow a lightsource.

All these bots are powered by a 3,3F Gold Cap ( F= farad). You can charge them with a regulated power supply

the two 5 mm red LED's it is capable of following a light source.

It is powered with two 3.3F Goldcaps. They can be charged in a few seconds. When they are charged, MAXIBUg gets "afraid" of light, and wanders of to go to play "in the dark". After a while, about 20 seconds (depending on the current used by the two motors ), the power has dropped, and it wants to "eat". It gets light attracted, and will turn and go to the light. When it gets there, it will recharge and still will be atrackted to the light until it reaches a trigger voltage , at which it gets "afraid"of the light again. This will go on all day until someone turns off the lightsource. While doing all this it also will backup when bumping into something.

Because of the "on-off" output of the first schmitt trigger, the inputs for the LDRs will switch. That's why it gets light atracted -light afraid. This also means that you cannot use IR diodes (like SHF205). You have to use LDRs !

In many ways, both the 74*240 and 74*245 are equally handy for BEAM use; both have 20 pins, and so the main difference that most folks will care about is that one inverts drive inputs, while the other doesn't. Out of curiousity, I decided to torture test the two chips to see how they compared under load.

1381s are CMOS voltage-controlled triggers -- these "gate" a source until the voltage is above some "trip" limit, at which point it is allowed onto a third pin

We use them as 3- or 5-volt triggers

This chip is often considered the heart of Nv net technology

One essential difference is that the Nv responds immediately to an input, and sends the output for a time duration -- the delay occurs AFTER the output is sent. The Nu responds to an input after a delay and sends the output continuously -- the delay occurs BEFORE the output is sent.

"on" first, then a delay, then "off"

delay, then "on", stays "on"

This is the 3 capacitor method.  I used this one in all my RC cars and many of the RC toys that I have taken apart use this method.

One of the easiest and most overlooked technique that can be done to lower motor noise is the twist your motor and motor power wires.  This in affect forces the magnetic fields to cancel each other out.

By placing a metal shield between your motors and radio can do wonders.  Also keep in mind that some metals shield better than others.   Carbon Steel shields several hundred times better than aluminum.  Dont use this shielding as a conductor or you may compound the problem.

Behavior-based robotics is quite simply the design of robots where there are no internal "models" of the environment. Instead, the robot's action is state-machine driven via inputs gleaned from the robot's sensors.