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Build this simple "electronic electroscope," a FET electrometer - 0 views
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This simple circuit can detect the invisible fields of voltage which surround all electrified objects
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The 1-meg resistor helps protect the FET from being harmed by any accidental sparks to its Gate lead. The circuit will work fine without this resistor. Just don't intentionally "zap" the Gate wire with a charged object or your charged finger.
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To test the circuit, charge up a pen or a comb on your hair, then wave it close to the little "antenna" wire. The LED should go dark. When you remove the electrified pen or comb, the LED should light up again.
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If you suspect that humidity is very high, test this by rubbing a balloon or a plastic object upon your arm. If the balloon does not attract your arm hairs, humidity is too high.
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This FET sensor is not an ideal educational device because it responds differently to positive than to negative.
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negative objects turn the LED off, it lights again when removed. positive objects make the LED bright, then dark when removed.
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Obtain a small capacitor with a value below 100 picofarads. Connect it between the FET gate lead and one of the other FET leads (doesn't matter which one.) This greatly reduces the sensitivity of the device
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Now make the circuit MORE sensitive. Obtain an alligator clip-lead, and connect it to the Gate lead of the FET. Let it hang loose without touching anything. You'll find that this has vastly increased the sensitivity of your FET circuit.
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Electronics Applications - 0 views
www.asc.vic.edu.au/...cations%20of%20electronics.htm
4star diode electronics ldr led photodiode sensor
shared by York Jong on 30 May 07
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The photodiode and phototransistor can be both photovoltaic (generators of potential difference) and photoconductive (modifiers of an electric current), depending on the application.
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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.
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When light shines on the LDR, it has low resistance and allows current to flow. When light does not shine on it, the LDR has a very high resistance, and a much smaller current will not flow through it.
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Photodiode - Wikipedia, the free encyclopedia - 0 views
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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.
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Photodiodes can be used under either zero bias (photovoltaic mode) or reverse bias (photoconductive mode)
Robot Hobby Circuits free electronic circuit links - 0 views
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Intermediate Robot Building - 0 views
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This book provides far more detail on the hardware aspects of robot building than any other I have seen to date and is worth picking up.
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"Intermediate Robot Building" offers the kind of real-world knowledge that only an experienced robot builder can offer--the kind of knowledge beginners usually have to learn through mistakes. In this book, you'll learn the value of a robot heartbeat and the purpose of the wavy lines in photocells.
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BEAM robotics - Wikipedia, the free encyclopedia - 0 views
BEAM Robotics - 34 views
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Reversing a motor without use of sensors - 0 views
www.solarbotics.net/...tutorials_nosensrevers.html
3star beam circuit electronics motor sensor theory
shared by York Jong on 27 May 07
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The motor is driven in either the forward or reverse direction, but will swap polarity if the motor encounters too sudden or great of a load
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Nv neuron variants - 0 views
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By just tying a neuron's bias resistor to Vcc, rather than to ground, you can make a "regular logic" (active high) Nv:
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Miller tutorial -- applications - 0 views
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Nu neuron basics - 0 views
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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.
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BEAM Pieces -- Integrated circuits - 0 views
library.solarbotics.net/...parts_elect_ic.html
5star beam collection electronics ic motor robot solar survey
shared by York Jong on 27 May 07
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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
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The '240 is often called "the bicore chip," because we can take advantage of the 240's inverters to turn a single 74*240 into a bicore
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The '240 also has tri-state outputs, so an enable line can be used to turn its outputs on and off simply (good for adding reversing capability to a 'bot).
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any *cores built with a 74*04 will require additional logic "downstream" to amplify the current to levels sufficient to drive a moto
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74HC/HCTxx non-buffers (74HC14 or 74HC04) draw about half of the current consumption, and have about half the drive current compared to HC / HCT buffer chips (74HC240 or 74HC245). Non-buffer chips are thus better for oscillators, say Nv and Nu applications; they are not suited for use in driving motors.
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The '245 is an octal buffer chip, and so has 8 channels of buffering power available for our misuse. This chip was designed for data transmission uses, but we'll misuse it as a motor driver chip
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The '244 provides us with 8 (thus the "octal") buffers, enableable in banks of 4. This is a very useful chip for amplifying small currents
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it can drive up to 4 motors in 2 directions each, or you can "buddy up" inputs and outputs to drive fewer motors at higher current
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it can drive up to 4 motors in 2 directions each, or you can "buddy up" inputs and outputs to drive fewer motors at higher current
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If you can't find 1381s locally, you might have better luck finding its European cousin, the TC-54 -- for details on it
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Note that if you need more than about 200 mA per motor, you'll need to use an H-bridge, or some similar motor driver
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The ideal BEAM circuit would use a low (2V-3V) voltage core and sensors combined with level shifting high (5-6V) volt motor drivers to maximize efficiency.
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BEAM Circuits -- 74*24x-based motor drivers compared - 0 views
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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.
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Maxibug, Minibug, Microbug - 0 views
home.wanadoo.nl/...maxibug.htm
5star 74x14 beam circuit diy electronics maxibug photopopper phototrope photovore robot tutorial
shared by York Jong on 27 May 07
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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.
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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 !
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The change in output is visualised with two red LEDs. When the LEDs are burning, the bot is "afraid" of light. They are mounted as eyes off the bot, that's why I used two off them. One LED will do also, but doesn't look nice !
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Short Period Astetics Intelligence - 0 views
home.wanadoo.nl/...others.htm
5star beam circuit diy electronics phototrope photovore robot tutorial
shared by York Jong on 27 May 07
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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.
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All these bots are powered by a 3,3F Gold Cap ( F= farad). You can charge them with a regulated power supply
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When ALI bumps into something it will go backward for a short time and then go forward in another direction, so they will find their way all alone.
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The first one is a light seeker and the second one is a line follower. This version I like very much.
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When you are making the line follower you need to place the small light bulb. The light seeker doesn't need it.
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When bumbing into something it can also reverse for several seconds. The time of going reverse can be changed. I've used 2M2 and 3,3 uF, this will give a reverse time of about 5 seconds
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When you "power on" Bully it will first go backwards for some time. After a few seconds it seems that it doesn’t know what to do, it looks like it’s shivering. Then it starts of going to the brightest lightspot it can see, first slowly and then like "in a hurry". When it reaches the lightspot it makes turns which make it look like it’s happy! In the time doing all this stuff, each bump into a obstacle makes it move backwards for a few seconds. The time doing this can be changed with the 10 uF elco. Smaller means less seconds and bigger means reversing for more seconds.
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A Bot With Peripheral Vision - 0 views
www.geocities.com/...PVRoller.html
5star beam behavior-based circuit electronics photopopper phototrope robot
shared by York Jong on 27 May 07
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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.
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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.
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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.
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The diodes between the photo-diodes create a constant voltage drop between the inputs of the inverters. They cause a dead band to exist between the thresholds of the two inverters. In a way they cause the circuit to act like a kind of window comparator. Without these diodes both inverters would always be in the same state. With them, there is a small range where their outputs are in opposite states.
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The Slave section has only two diodes (or one LED) between the photo-diodes. This makes it respond to smaller differences in light levels than does the Master part of the circuit
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Cheesy works very well. I?ve had fun making him chase a spot of light from a flashlight around on the floor. He has even been able to detect and react to the flashlight spot on the floor of the brightly lighted lab where I work.
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74*14-based photopopper circuits - 0 views
library.solarbotics.net/...bot_popper_14.html
5star 74x14 beam circuit electronics maxibug photopopper phototrope robot
shared by York Jong on 27 May 07
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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:
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I tried the same setup with the 74*240 (with an extra inverter per motor) and 7404, but the 74HC14 seems to work best.
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John-Isaac Mumford started off by simplifying the Maxibug design, and wound up with an entirely new circuit -- Mazibug
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The tactiles switches behave even more strongly: if a switch is closed then the bot turns away unconditionally. If both switches are closed the robots reverse straight back regardless of light level.
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When the robot bumps into something on one side, it over-rides all the photodiode circuits and reverses the motor on the OPPOSITE side
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From the title it would appear that all 4 photodiodes face forward but the 2 inner PDs face directly forward and the outer 2 are angled to the left and right
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74*240-based photopopper circuits - 0 views
library.solarbotics.net/...bot_popper_240.html
5star 74x240 beam circuit electronics maxibug photopopper phototrope robot
shared by York Jong on 27 May 07
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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.
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Two leaded phototransistors can also be used but may require extra shielding to reduce light current in the bridge to acceptable levels
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The monocore capacitor is for positive feedback for fast switching between the two motors and to slow down and avoid high frequency oscillations.
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R2 together with C2 limits the maximum frequency of the monocore and motor drivers when the light is bright and the sensors are equally lit
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R3 together with C2 sets the minimum frequency of the waggle even in the complete dark which is more interesting than twirling endlessly in a circle.
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Having said that, maxibug is not perfect: it churns its wheels while feeding and does not back out of the feeding station when full. CD MaxiBug v5 uses just a few more parts but has powerful and efficient motor drivers, its motors are off while feeding, and it backs up when full.
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Reduce Motor Noise - 0 views
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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.
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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.
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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.
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Place your high current wires away from sensitive areas and antennas. Don't run the wire parallel with wires that are used as signaling in your micro controller. If you must its best to have them cross at 90 degrees.