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York Jong

Flashing LED - BEAM Wiki - 0 views

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

Build this simple "electronic electroscope," a FET electrometer - 0 views

  • This simple circuit can detect the invisible fields of voltage which surround all electrified objects
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  • The Gate acts as an antenna, so leave it unconnected.
  • 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.
  • 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.
  • 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.
  • This FET sensor is not an ideal educational device because it responds differently to positive than to negative.
  • negative objects turn the LED off, it lights again when removed. positive objects make the LED bright, then dark when removed.
  • 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
  • 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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    This simple circuit can detect the invisible fields of voltage which surround all electrified objects. It acts as an electronic "electroscope.
York Jong

LEDs - BEAM Wiki - 0 views

  • 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.
York Jong

Maxibug, Minibug, Microbug - 0 views

  • 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 !
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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 !
York Jong

Getting Started With Crickets - 0 views

  • 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.
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  • the Cricket's green LED light goes on while the Cricket is executing commands.
  • You can "launch" a procedure directly from the Cricket by pressing the white button on the Cricket.
  • You can send information from the Motor/Sensor Cricket back to the computer using the send instruction.
York Jong

「單」晶片控制多組 PWMs - 160 views

作者: ykjiang (York) 看板: Robotics 標題: Re: 「單」晶片控制多組 PWMs 時間: Wed Dec 13 00:17:04 2006 ※ 引述《happosai (八方齋)》之銘言: > 其實用 FPPA 產生 PWM 訊號一點都不難,因為那一顆CPU就只負責 > 產生PWM訊號,講白一點都是死迴圈,真正 update PWM 是另外一顆 > 負責,所以程...

embedded motor pwm

York Jong

A Bot With Peripheral Vision - 0 views

  • 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.
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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.
  • 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
  • Basically, what I did was to stack one SC-H on top of another
  • I?m using a 74 HC 139 to direct the outputs of the M/S SC-H circuit to the appropriate motor(s)
  • 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.
    • York Jong
       
      Stacking separate Sensor/Behavior
York Jong

Diode - 0 views

  • 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
York Jong

Electronics Applications - 0 views

  • 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.
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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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