Human Sensing Circuits

This highly sensitive movement detector is designed from bipolar transistors and draws a curren..

Views: 31 | Votes: 98 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Aug 8, 2012 |

The change in ambient light triggers the alarm by changing resistance of LDRl and LDR2. ..

Views: 438 | Votes: 6 | Comments: 0 | Rating: 7 | Rank: 4 | Added: Jul 27, 2012 |

This touch-actuated switch stays on as long as you keep your finger on the touch plate. Rl sets the input impedance to a high 22 MO. Ql picks up stray signals coupled through your body to the touch plate and amplifies them to tum on Q2, which turns on lamp drivers Q3 and Q4. Lamp 11 is any small12-V lamp, such as a No. 53-12 V 120 mA. R4 and Cl add a small amount of hysteresis (delay) to keep the light from constantly flickering. ..

Views: 20 | Votes: 72 | Comments: 0 | Rating: 1 | Rank: 5 | Added: Jul 25, 2012 |

Integrated circuit gates ICl-a and TCl-b form a monostable, whose time constant is determined by C2 and R3. When the transmitter is dekeyed (and then almost immediately rekeyed) point TX+ goes low and takes pin 1 low for a short time. This triggers the start of the timing period controlled by C2/R3. The capacitor C2, charges via R3 until the trigger point of gate ICl-b is reached. At this point, the monostable changes state and pin3 goes low again. On the prototype, this.....

Views: 5 | Votes: 72 | Comments: 0 | Rating: 0 | Rank: 5 | Added: Jul 5, 2012 |

This circuit detects an object passing in one direction but ignores it going the opposite way. Two sensors define the sense of direction. The object blocks the light to phototransistor Ql or Q2 first dependent on the direction of approach. When the object passes Ql then Q2, an output pulse is generated at D; while no pulse is seen at D as the object passes Q2 then Ql. ..

Views: 716 | Votes: 23 | Comments: 0 | Rating: 8 | Rank: 4 | Added: Jun 11, 2012 |

? simple heart-beat transducer can be made from an infrared LED and an infrared phototransistor. ?t works because skin acts as a ref1ecti?e surface for infrared light. The lR ref1ecti?ity of one's skin depends ??? the density of blood in it. Blood density rises and falls with the pumping action of the heart. ..

A 3-x -3-inch piece of circuit board, or similar size metal object which functions as the pick-up sensor, is connected to the gate of Ql. A 100-MD resistor, R2, isolates Ql"s gate from Rl, allowing the input iropedance to remain very high. If a 100MO resistor cannot be located, just tie five 22-MO resistors in series and use that combination for R2. In fact, R2 can be made even higher in value for added sensitivity. ..

Views: 23 | Votes: 47 | Comments: 0 | Rating: 7 | Rank: 5 | Added: Jun 4, 2012 |

In This circuit, two 567 tone decoders are used. One is an oscillator, the other is a detector. Bridging TP1 and TP2 causes U2 to receive Ul`s signal, which causes pin 8 of U2 to go low...

Views: 5 | Votes: 1 | Comments: 0 | Rating: 4 | Rank: 5 | Added: May 12, 2012 |

Right- and left-channel signals pass through 1 C4-a and -b buffer amps into active crossover IG5; low frequencies are sent to the IC6-c mixer, and middle and high frequencies are sent to the analog delay lines of 1C1 and 1C2. That output passes through lC6-a and -d to filter high- frequency sample steps. 106-b signals are remixed with low frequencies by 106-c and are sent to final out via IC4-c, and -d buffers. One channel (R) is a variable-delay circuit, using an analog.....

Views: 15 | Votes: 71 | Comments: 0 | Rating: 6 | Rank: 5 | Added: Apr 20, 2012 |

This circuit uses a surplus geophone to detect human footsteps from 100 feet away. It was designed for monitoring the Mexico/USA border. This preamp part of the system draws about 50 microamps from a 12 volt supply...

A home made geophone is made from a strong magnet, a coil of wire and a rubber band. The circuit is sensitive enough to detect the vibrations of a nearby foot stomp. It could be used as an earthquake detector...

This is an image Schematic. No Description available...

A simple circuit with which we have the possibility opening and closing the RL1 contacts. He becomes touching a small metal surface. Clue of situation that is found RL1, is become by the Led D3. The supply of circuit is +12V, the IC1 is supplied with 3.9V fall of voltage that is ensured by combination R5 and zener D2. For more good restoration perhaps it should adaptation of R1 value. ..

Our circuit is amplifying the current flowing through your finger (when it touches the touch plate) 10,000 times and this is sufficient to illuminate the LED. The current flowing through your finger (when touching the touch plate) is only a few microamps and this is not enough to illuminated the Light Emitting Diode (LED). We need an amplifier with considerable gain to get the LED to light and this is what the circuit does. You can alter the brightness of the LED by.....

Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door. Anyone grabbing the knob from the outside is detected by the electrical capacitance change that occurs from the human hand contact between the knob and the box. Almost all of the commercial devices sold use a more expensive and power consuming radio frequency circuit approach to.....

With this circuit we can change the brightness of lamb, with a only key of touch. The key of touch is connected in the circuit, center of which is a special completed IC1, which is the S566B of SIEMENS. This IC, it processes the information of duration of touch and then it checks the brilliance of lamb, according to this information. If we touch upon the key for a small period of time (60 until 400 ms), the lamb simply only changes situation, that is to say from OFF in ON.....

This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load...

These ultrasonic circuits are all quite old: my notes date them at mid-70s so they don`t use ICs. Nevertheless there are several places where an op-amp would possibly simplify things. Despite their age I hope they are of interest: certainly basic principles don`t change...

This circuit processes the amplified signals from the footstep detector circuit and activates a microprocessor when the circuit detects footsteps. At has an adjustable sensitivity...

A touch switch is a switch that is turned on and off by touching a wire contact, instead of flicking a lever like a regular switch. Touch switches have no mechanical parts to wear out, so they last a lot longer than regular switches. Touch switches can be used in places where regular switches would not last, such as wet or very dusty areas...