Wiring Material: sensor

Monday, October 13, 2014

Latest new Oxygen Sensor Simulator Oxygen Simulator Sensor

The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate. The big "V" is a digital voltmeter (not shown in the pictures). Using a smaller value for C1, perhaps 4.7 uF, will make the circuit oscillate faster and might be more like a real oxygen sensor (a new sensor switches more often than an old one).

The schematic diagram for the simulator. Closing the switch engages the simulator. Turning the knob clockwise simulates a lean condition, turns the LED off, and the car should start running rich to compensate. The big "V" is a digital voltmeter (not shown in the pictures). Using a smaller value for C1, perhaps 4.7 uF, will make the circuit oscillate faster and might be more like a real oxygen sensor (a new sensor switches more often than an old one).

The schematic diagram of the adapter cable and oxygen sensor. Note the heater is shown as a resistor, mine measured about 7 ohms.

Friday, September 26, 2014

Temperature Sensor Circuit for Remote Distance Applications

The circuit shows a temperature sensing device which can be used to indicate at a remote point when the temperature passes through a certain value or to give an alarm when this occurs.
The sensing unit itself contains a 2N930 transistor. The base-emitter voltage of this device appears across R1 and (as the base current is far less than the collector current) the voltage at the upper end of R2 will be the emitter-base voltage multiplied by (R2 + R1)/Rl.

The base emitter volt· age changes with T a temperature coefficient of —2.2mV/°C and this change is multiplied by the same factor before being applied to the LM339 circuit. The potential at point A is set by the resistors R3 and R4. As _the temperature of the sensor transistor rises, the voltage at point B falls. At the time this voltage falls below that at point A, the output of the LM339 voltage comparator will go high. lf, however, the input connections to the LM339Aare reversed, the output will go low when the temperature of the sensor falls below the preset point.

The LM339 contains four separate voltage comparators in one package; only one of these comparators is used in the circuit shown. The other three comparators could be used with another three temperature sensing transistors so that an indication is given when the temperature passes through three other preset values. The`value of R5 should be chosen so that the current passing through the remote sensor unit is about 10pA. lf the temperature range over which operation is required is narrow, the ratio R2/R1 may be large so that the system is- very sensitive to small temperature variations. A potentiometer may be substituted for R3 and R4 so that the temperature at which the comparator switches is variable.

The voltage at point B is,highly linear over a very wide temperature range (about -65°C to +150°C) and there- fore the potentiometer which replaces R3 and R4 can be given a linear calibration. A feedback resistor may be connected from the output to the non- inverting input to provide a small amount of hysteresis (so that the temperature at which the output changes when the temperature is rising is different from that when it is falling); one then has the basis of a thermostat. ‘ The output current has a maximum value of about 15mA.

Thursday, August 21, 2014

Electronic Components As Light Sensor

Electronic components are included in the category of light sensors is LDR, Photo Transistor, Photo Diode, Infrared Receiver. The function of the electronic component is to detect the intensity of light received by the component. The light sensor is often used in electronic equipment such as on television, light a light switch, light intensity measuring instrument.

Electronic Components As Light Sensor

Tuesday, August 19, 2014

Line Following Robot Sensor

This Line Following Robot sensor or surface scanner for robots is a very simple, stamp-sized, short range (5-10mm) Infrared proximity detector wired around a standard reflective opto-sensor CNY70(IC1). In some disciplines, a line following robot or an electronic toy vehicle go along a predrawn black line on a white surface. In such devices, a surface scanner, pointed at the surface is used to align the right track.

IC1 contains an infrared LED and a phototransistor. The LED emit invisible infrared light on the track and the phototransistor works as a receiver. Usually, black colored surface reflects less light than white surface and more current will flow through the phototransistor when it is above a white surface. When a reflection is detected (IR light falls on the phototransistor) a current flows through R2 to ground which generates a voltage drop at the base of T1 to make it conduct. As a result, transistor T2 start conducting and the visual indicator LED(D1) lights up. Capacitor C2 works as a mini buffer.

Line Follower Robot Scanner Schematic

After construction and installation, the scanner needs to be calibrated. Initially set P1 to its mechanical centre position and place the robot above the white portion of the track. Now slowly turn P1 to get a good response from D1. After this, fine tune P1 to reduce false detection caused by external light sources. Also ensure that the LED remains in off condition when the sensor module is on the blackarea. Repeat the process until the correct calibration is achieved.

The red color LED (D1) is only a visual indicator. You can add a suitable (5V) reed relay in parallel with D1-R4 wiring after suitable alterations to brake/stop/redirect the robot. Similarly, the High to low (H-L) transition at the collector of T2 can be used as a signal to control the logic blocks of the robot. Resistor R1 determines the operating current of the IRLED inside IC1. The sensing ability largely depends on the reflective properties of the markings on the track and the strength of the light output from IC1.