Friday, April 6, 2012

Radios Clock Time Signals

Radio Clock listens to radio time signals from your radio and corrects the time on your PC clock. Radio Clock enables you to decode the time signals sent by various LF and HF radio stations in the standard frequency and time service. Radio Clock uses your PC to display the time code received from the radio station, using a suitable receiver, and compares it with the local time on your PC.

At present Radio Clock can decode the following time signals.

If you register Radio Clock, you can set it to correct your PC clock time automatically. To enjoy this extra feature, you can register Radio Clock here.

Radio Controlled Clock
On these pages, I will introduce a Radio Controlled Clock. But this clock works with Japanese radio clock system so the country out of Japan can not use this equipment just as it is. Please arrange in the system in your country by yourself referring to the contents to carry on these pages.

Pictures Radio Controlled Clock and Schematic

See more: Infrared Light Photo-Detector - Dynamic Metal Detector
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Thursday, April 5, 2012

Relay Output Proximity Sensor Circuit

This is a design circuit of relay output proximity sensor that can be used in oscillator. This is the figure of the circuit;

Q1 is used as an oscillator around 300 kHz. R9 is set so that the oscillator just begins to run. An object near the antenna will load the circuit down, and stop the oscillations. This is detected by bufferQ2, diodes D1 and D2, and this activates relay driver Q4, which operates the relay. [Circuit diagram source:]   
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Plants Watering Watcher Circuit

Here’s a design circuit for plants water monitoring. This is a simple form for the circuit. IC1D is a CMOS Schmitt trigger oscillator at about 2KHz. It starts and continues to oscillate with a supply down to 1.24V (the lowest output voltage of my LM317 variable power supply) or less. This is the figure of the circuit;

IC1B is a Schmitt trigger NAND gate. Its output is low only when both inputs are at, or higher than the upper Schmitt trigger threshold voltage. With 47 ohms or less between the probes, an input is always low, so the output is always high. With a resistance of only R8 between the probes, the voltage across C3 is high most of the time, so the gate output is low for ½ the oscillator period. With a resistance that is halfway, then C3 is charged high by that resistance when the oscillator output is high, then is discharged when the oscillator output is low. When C3 is being discharged, then pin 12 of the gate is high, and pin 13 is also high until the discharging voltage of C3 reaches the lower Schmitt threshold voltage. During this time, the gate's output is low. So the low time of the gate output depends on the value of the resistance between the probes. This is Pulse-Width-Modulation of the low output of the gate. IC1C is another CMOS Schmitt trigger oscillator at about 2Hz. D1 and R4 discharge C4 quickly so that its output is low for only about 15ms with a 3V battery, and about 25ms with a 2V battery.
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Pellistors Circuit

Pellistors employ catalytic combustion to measure combustible gases or vapours in air up to the Lower Explosive Limit (LEL)* of the gas. The standard sensor consists of a matched pair of elements, typically referred to as a detector and compensator (reference element). The detector comprises a platinum wire coil embedded within a bead of catalytic material. The compensator is similar except that the bead does not contain catalytic material and as a consequence is inert. This is a figure of the block diagram of the pellistors;

Both elements are normally operated in a Wheatstone bridge circuit, that will produce an output only if the resistance of the detector differs from that of the compensator. The bridge is supplied with a constant dc voltage that heats the elements to 500-550°C. Combustible gases are oxidised only on the detector element, where the heat generated increases its resistance, producing a signal proportional to the concentration of combustible gas. The compensator helps to compensate for changes in ambient temperature, pressure, and humidity, which affect both elements equally. Most pellistors have the pairs of elements housed in separate metal cans. In a complete gas detector (to be used in a potentially explosive atmosphere) the cans will normally be mounted inside a flameproof enclosure consisting of a metal sinter and housing. This enclosure allows gas to reach the sensor whilst ensuring that the hot sensor elements cannot ignite an explosive gas mixture. Since the design here is critical, it is usual for the enclosure to be certified to National Standards by a recognised test house. This can be a lengthy and costly exercise especially if certification is sought in different countries. As an alternative complete detectors are available with both elements mounted inside a flameproof enclosure approved to the latest European (ATEX) and North American (CSA & UL) standards.

Detection of explosive atmospheres relies on the accurate measurement of combustible gases below the LEL concentration. Safety applications, therefore, are not generally concerned with measuring the volume concentration of gas. Measurements are more usually expressed as a percentage of the LEL concentration of the gas (%LEL). Most combustible gas detection techniques are designed to detect a wide range of gases. Ideally the output of a sensor will be independent of the gas being measured. In reality, however, the variation in physical properties affect the output. Catalytic oxidation sensors are no exception, so the response a pellistor gives to the same volume concentration of different gases will vary. However when exposed to the same %LEL concentration of different gases, the variation in output is fairly small compared to other detection techniques. As safety applications are interested only in %LEL measurements this is a major advantage.

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Infrared Optical Proximity Switch Circuit

This is a design circuit that can be used to detect objects by reflected infrared light. It can be built into a cylindrical enclosure just like an inductive proximity switch. This is also useful as a level detector for colored liquids like oil. This has some immunity to ambient sunlight as it detects ac pulses. This is the figure of the circuit;

The proximity switch can work for a wide range of power, from 8v to 18v DC, D3 protects reverse power supply connections, and U1 regulates the supply to +5v , -5v is derived from U2 555 oscillator which serves dual purpose. IC 555 is used as an astable oscillator and it flashes the Infra red LED D1 at a high speed, The object close to this LED reflects the light along with the ambient light which may also be sunlight. The infra red diode D2 detector gets the reflected light from LED and some ambient light, The forward voltage drop of D2 will vary with the amount of light falling on it. Ambient light causes a DC component and the pulsing light from D1 causes an AC component. 

The capacitor C6 blocks DC and only transfers AC pulses if any to opamp amplifier U3A whose gain is set by R18, D9 rectifies the pulses to DC and this DC voltage is used by opamp comparator U3B which drives Q1 through Q2 for an open collector output for relays. LED D7 turns on when relay Output is high. R14 and R13 can be replaced with potentiometer for threshold adjustment if required. Connect 12v DC supply to +V and GND Ports, Connect a relay coil Between OUT and GND Ports, you can use the relay contacts as you require to turn on a lamp, heater, fan or motor. If all connections are ok and ICs are working you should see a +5V at U3 pin8 VCC and around -4 to -5 at U3 pin4 VDD.
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Energy Leak Detector Circuit

Here’s a design circuit for sensitive circuit is basically a comparator, detecting very slight temperature changes in respect to the ambient temperature. It was primarily intended to detect draughts around doors and windows that cause energy leaks but can be used in many other ways, when a sensitive temperature change detector is needed. Two LEDs are used to signal if the temperature change is pointing above (Red LED) or below (Green LED) the ambient temperature.

IC1 acts as a bridge detector and amplifier: its output voltage raises when temperature increases and vice-versa. This happens because the n.t.c. resistor R2 reduces its resistance value as temperature increases and vice-versa, therefore unbalancing the bridge formed by R1, R2, R4, R5. IC2A and IC2B form a window comparator and R8 is the sensitivity control.

Before starting a measurement the circuit must be balanced by means of R1 in order to obtain that both LEDs are off. If R8 is set to zero resistance the circuit sensitivity will be at maximum and one of the LEDs will illuminate when a very slight difference in temperature will be detected. As R8 value is increased the circuit sensitivity will decrease.

R1_____________22K  Linear Potentiometer (See Notes)
R2_____________15K  @ 20°C n.t.c. Thermistor (See Notes)
R3_____________10K  1/4W Resistor
R4,R5,R7,R9____22K  1/4W Resistors
R6____________220K  1/4W Resistor
R8______________5K  1/2W Trimmer Cermet
R10___________680R  1/4W Resistor
C1_____________47µF  63V Electrolytic Capacitor
D1_____________5mm. Red LED
D2_____________5mm. Green LED
IC1___________TL061 Low current BIFET Op-Amp
IC2___________LM393 Dual Voltage Comparator IC
P1_____________SPST Pushbutton
B1_______________9V PP3 Battery
Clip for PP3 Battery
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Simple Metal Detector

It's a simple metal detector design that has the quite good characteristics. the principle of operation which one differs from the classic schemes (BFO, transmit-receive known as "two-boxes" metal detector, inductive).

The dynamic mode is used to find targets in interference environment. There is known from theory of signal filtration that if signal shape is determined we can construct optimal filter - the best one for extracting the signal with maximum signal/noise ratio. This filter is known as optimal matched filter. In our device we realized digital optimal matched filter as part of microcontroller software. The filter parameters are optimized for effective ferro- and nonferro targets detection on 0.5-1.0 m/s velocity of sensor.

Features of the Metal Detector:
Power supply .............................4.5-6V;
DC consumption .......................15 mA;
Indication ...................................sound + 8 LEDs;
Modes ........................................static or dynamic;

Metal Detector Schematic, Layout and PCB

Switches controled (versions V1.9 and V2.0 of firmware):
S0: reset device;
S1: reserved;
S2: on - threshold hight, off - threshold low;
S3: measuring time on - 30ms, off - 120ms;
S4: selftuning on/off (in dynamic mode only);
S5: mode on - static, off - dynamic.

Metal Detector Coil Design

Approx. 100 curls 200 mm in diameter. Cupper wire in isolation 0,35 mm diameter

Source : Metal Detector
See More: Infrared Light Photo-Detector
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