Secret Diagram: sensor

Showing posts with label sensor. Show all posts

Friday, 17 March 2017

Fog Lamp Sensor

For several years now, a rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under foggy conditions.

Circuit diagram :

Fog Lamp Sensor Circuit Diagram

When this fog lamp is switched on, the fog lamp of the pulling vehicle must be switched off to avoid irritating reflections. For this purpose, a mechanical switch is now built into the 13-way female connector in order to switch off the fog lamp of the pulling vehicle and switch on the fog lamp of the trailer or caravan. For anyone who uses a 7-way connector, this switching can also be implemented electronically with the aid of the circuit illustrated here.

Here a type P521 optocoupler detects whether the fog lamp of the caravan or trailer is connected. If the fog lamp is switched on in the car, a current flows through the caravan fog lamp via diodes D1 and D2. This causes the LED in the optocoupler to light up, with the result that the phototransistor conducts and energises the relay via transistor T1. The relay switches off the fog lamp of the car.

For anyone who’s not all thumbs, this small circuit can easily be built on a small piece of perforated circuit board and then fitted somewhere close to the rear lamp fitting of the pulling vehicle.

Author :Harrie Dogge - Copyright : Elektor

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Wednesday, 11 January 2017

LED Photo sensor

It is not always necessary to use special photoresistors or phototransistors to make light-sensitive switches. Although it is not well known, normal visible-light and infrared LEDs will also work. A voltage that depends on the intensity of the natural or artificial illumination falling on the LED can be taken from the anode of the LED. This behaviour can be easily verified by connecting a DVM or oscilloscope directly to the two leads of the LED.

Circuit Diagram:

LED Photosensor Circuit Diagram

Since the load on the photoelectric potential should be kept as small as possible, a JFET is used here as a buffer. The type used is not critical; similar transistors should work equally well. The buffered voltage is fed to the inverting input of comparator IC1. The threshold voltage can be adjusted to meet the desires of the user by means of the potentiometer. A pull-up resistor is connected to the com-parator output, since the LM393 has an open-collector out-put. The supply voltage may be chosen anywhere in the range of 5 to 9 V.

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Thursday, 24 November 2016

Experimental Hall Sensor

Hall sensors can of course be purchased but making them yourself is far more interesting (and satisfying)!
According to the theory the crucial thing is to use a touch layer that’s as thin as possible; the length and width are unimportant. An ‘obvious’ starting point for our trials would be copper, which in the form of printed circuit board material is easy to find and handle. Copper-clad board may be obvious but not ideal, because it has a very weak Hall constant.

Nevertheless we should be able to use it to demonstrate the Hall effect by using very powerful magnets in our sensor.To achieve detection we need the highest possible level of amplification. In the circuit shown here the voltage amplification is set by the relationship of the two feedback resistors of the first op-amp. With the values given (2.2 MΩ and 330 Ω) produce a gain of 6,667.

Experimental Hall Sensor Circuit Diagram :
Experimental Hall-Sensor-Circuit Diagram

This also creates a convenient bridge connection for taking measurements. The trimmer potentiometer allows fine adjustment. With zero set ting that’s accurate to within millivolts we could use this test point to measure Hall voltages of well below a microvolt. Finally in this way we could also measure the flux density of a magnet.

Copper has a Hall constant of AH= –5.3·10-11m3/C. The thickness of the copper layer is d = 35 µm. The Hall voltage then amounts to:VH= AH× I × B / d

When the field B= 1 T and current I= 1 A a Hall voltage of VH= 1.5 µV is produced. The6,667-fold gain then achieves a figure of 10 mV. The circuit thus has a sensitivity of 10 mV per Tesla. That said, adjusting the zero point with P1 is not particularly easy. The amplifier has a separate power supply in the form of a 9 V battery (BT1). To take measurements we connect a lab power supply with adjustable output current (BT2) to the Hall sensor (the copper surface) and set the current flowing through the sensor to exactly 1 A. Then the zero point must be adjusted afresh.

Next we place a strong Neodymium magnet below the sensor. The output voltage of the circuit should now vary effectively by several millivolts. Note that there are several effects that can influence the measurements we take. Every displacement of the magnet will pro-duce an induction voltage in the power feed wires that is significantly greater than the Hall voltage itself. Every time you move the magnet you must wait a while to give the measurements time to stabilise. With such small voltage measurements problems can also arise with thermal voltages due to temperature variations. It’s best not to move and inch — and to hold your breath as long as possible!

Author : Burkhard Kainka - Copyright : Elektor

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Thursday, 10 November 2016

AMN12111 PIR Motion Sensor

PIR movement sensor module (Passive Infra Red) motion detection sensor AMN12111 is the smallest of objects the size of its shape. PIR motion sensor module (Passive Infra Red) AMN12111 fresneal come equipped with a lens. PIR motion sensor module (Passive Infra Red) AMN12111 has advantages can be directly connected to the microcontroller or other actuator driver.

PIR movement sensor module (Passive Infra Red) AMN12111 has a sensitivity that is very sensitive to changes in motion around it. PIR movement sensor module (Passive Infra Red) AMN12111 very suitable when applied to security systems. The price of the PIR movement sensor module (Passive Infra Red) AMN12111 not quite expensive. readily available in the market. For those of you who want to make a motion detection sensor. PIR movement sensor module (Passive Infra Red) AMN12111 is much easier and more practical than you have to make a series of Infra Red with the Tx and Rx.

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