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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 !

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.

Usually, the operating system takes all the values from the sensors, averages them, then finds the one that is the furthest away from that average

The Ant Farm is built next to a very large window that faces east. As a result, with the lab lights off, the brightest light source is always to the east. The robots can use this as a reference and then find all the other directions.

The current through a photodiode is directly proportional to the light intensity

The photodiode and phototransistor can be both photovoltaic (generators of potential difference) and photoconductive (modifiers of an electric current), depending on the application.

A reverse-biased photodiode operates in what is called photoconductive mode, since the conduction of the semiconductor junction varies with the illuminating light intensity.  If the reverse-biased voltage is relatively large (i.e. several volts) the reverse-biased photodiode will have a very fast response time (much faster than an LDR) and is suitable for detecting light signals that vary down to a time scale of a fraction of a microsecond.

pseudocode: read left_photoresistor read right_photoresistor if left_photoresistor detects more light than right_photoresistor then turn robot left if right_photoresistor detects more light than left_photoresistor then turn robot right if right_photoresistor detects about the same as left_photoresistor then robot goes straight loop

Photovore Algorithm, Improved This algorithm does the same as the original, but instead of case-based it works under a more advanced Fuzzy Logic control algorithm. Your robot will no longer just have the three modes of turn left, turn right, and go forward. Instead will have commands like 'turn left by 10 degrees' or 'turn right really fast', and with no additional lines of code! pseudocode: read left_photoresistor read right_photoresistor left_motor = (left_photoresistor - right_photoresistor) * arbitrary_constant right_motor = (right_photoresistor - left_photoresistor) * arbitrary_constant loop

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.

A flashing LED is just an LED with a built-in microcircuit to cause it to flash periodically.

Like other LEDs, FLEDs are light-sensitive, and so flash faster in brighter light.

Like other LEDs, FLEDs are light-sensitive, and so flash faster in brighter light.

The Sharp IR Range Finder works by the process of triangulation. A pulse of light (wavelength range of 850nm +/-70nm) is emitted and then reflected back (or not reflected at all). When the light returns it comes back at an angle that is dependent on the distance of the reflecting object. Triangulation works by detecting this reflected beam angle - by knowing the angle, distance can then be determined.

The IR range finder reciever has a special precision lens that transmits the reflected light onto an enclosed linear CCD array based on the triangulation angle.

The Sharp IR has a non-linear output. This means that as the distance increases linearly (by set increments), the analog output increases/decreases non-linearly.

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.

This adapted photodiode is not as sensitive as large area types so C2 may need to be reduced to 0.01uF while the value of R2 and R3 can be increased by a factor of 10.

Two leaded phototransistors can also be used but may require extra shielding to reduce light current in the bridge to acceptable levels

basic photopopper functions plus reverse -- all on a single chip

To use a photodiode in its photoconductive mode, the photodiode is reverse-biased; the photodiode will then allow a current to flow when it is illuminated.

LEDs can be used as photodiodes

FLEDs are light-sensitive, and so flash faster in brighter light

Note that the resistor value of the pull-down resistor affects the voltage at pin 3 of the Furby's connector. We used a 1k ohm resistor to make it less sensitive to light (since we're now operating with it open to ambient light).

In the above diagram, a 20k ohm resistor is used as the pull-up resistor. You can, however, use any resistor as the pull-up resistor as long as the resistance is high enough to protect the circuit.

This simple circuit can detect the invisible fields of voltage which surround all electrified objects

The purpose of a solar engine is to act like a power "savings account" -- a small trickle of incoming energy is saved up until a useable amount is stored

A solar-powered robot can be made to work, even in relatively-low light levels

Solar cell size is minimized

LEDs can be used as photodiodes (tho' their sensitivity is relatively low, so they're only useable this way in very bright conditions). When light is applied to an LED the anode sources current and becomes positive.

camera-based vision system (for light detection and navigation) two microphones, binaural hearing beat detection (allows pleo to dance and listen to music) - this feature was removed but may be added on again. eight touch sensors (head, chin, shoulders, back, feet) four foot switches (surface detection) fourteen force-feedback sensors, one per joint orientation tilt sensor for body position infrared mouth sensor for object detection into mouth infrared transmit and receive for communication with other Pleos Mini-USB port for online downloads SD card slot for Pleo add-ons infrared detection for external objects 32-bit Atmel ARM 7 microprocessor (main processor for Pleo) 32-bit NXP ARM 7 sub processor (camera system, audio input dedicated processor) four 8-bit processors (low-level motor control)

Reverse bias induces only little current (known as saturation or back current) along its direction. But a more important effect of reverse bias is widening of the depletion layer (therefore expanding the reaction volume) and strengthening the photocurrent. Circuits based on this effect are more sensitive to light than ones based on the photovoltaic effect and also tend to have lower capacitance, which improves the speed of their time response. On the other hand, the photovoltaic mode tends to exhibit less electronic noise.

Photodiodes can be used under either zero bias (photovoltaic mode) or reverse bias (photoconductive mode)

the Cricket's yellow LED flashes when the Cricket is sending infrared signals.

You can type any Cricket Logo instruction in the Cricket Logo Command Center, and it will be immediately transferred to the Cricket and executed.