Magnetic circuits

Magnetic proximity sensor / detector

Here is an interesting circuit for a magnetic proximity switch which can be used in various applications. The magnetic proximity switch circuit, in principle, consists of a reed switch at its heart. When a magnet is brought in the vicinity of the sensor (reed switch), it operates and controls the rest of the switching circuit. In place of the reed switch, one may, as well, use a general-purpose electromagnetic reed relay (by making use of the reed switch contacts) as the sensor, if required. These tiny reed relays are easily available as they are widely used in telecom products. The reed switch or relay to be used with this circuit should be the normally open type. When a magnet is brought/placed in the vicinity of the sensor element for a moment, the contacts of the reed switch close to trigger timer IC1 wired in monostable mode. ..

RF wireless allarm magnetic switch PIC16F84

This circuit was formed to create a wireless alarm from a normal magnetic contact. By fixing the magnet to the leaf of a door, or swing of a drawer, it is easy to reveal the opening. To transmit the signal to a control anti-theft we modify the circuit of a remote control to activate it only for as long as necessary . Without the change, leaving the door open for the batteries would run out in a few hours! This transmitter is powered by a battery of 9 volts for a period of one year. You can connect to any kind of contact , including that of infrared sensors (PIR) to create a wireless burglar alarm. Every time one of its three entrances is closed, is a radio code to entremets Nutchip or any other circuit compatible with the encoding MM53200 , UM3750 or UM86409 . This diagram illustrates a remote fixed codes , ready to work immediately without adjustments. Moving a jumper, you can also get codes like...

The layout of a typical magnetoresistive chip (parent device 174B) is shown in Figure 1, and is for example the chip used in the ZMY20 sensor. Thin film stripes are a characteristic feature of a magnetoresistive chip. These stripes are made by photolithography and consist of Permalloy (Ni81Fe19), a magnetic material evaporated on an oxidised silicon wafer...

his Design Idea describes a virtual instrument that uses a desktop or notebook computer with an analog data-acquisition card and National Instruments` (www.ni.com) LabView software (Version 7.1 or above). In operation, the software extracts B-H-loop information, core losses, and other magnetic parameters at a reasonable cost per measurement...

Isolated flyback converters usually evoke thoughts-or bitter memories-of custom transformers, slipped delivery schedules, and agency-approval problems. Off-the-shelf flyback transformers carry isolation ratings of only 300 to 500V and rarely of as much as 1 kV. Gate-drive transformers are readily available from stock with high isolation ratings and low cost, but they are wound on ungapped cores, have high inductance (500 µH to 2 mH), and quickly saturate in a normal flyback-converter circuit...

You can assemble a precompliance (or even full compliance) magnetic field immunity test system in a few hours using common laboratory instruments, a 100-W audio amplifier, some white PVC Schedule-40 3/4-in. water pipe, some wood, and a copper or aluminum sheet...

When optimally tuned, it will propel a small slug about 1.5 metres high, or 2.5 metres horizontally. IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15 is taken low through the "Fire" button. IC2 then sequences through outputs Q1 to Q7, to feed power transistors TR1 to TR4, which fire electromagnets L1 to L4 in rapid sequence...

Power-supply designers usually like flyback converters to operate in DCM (discontinuous-conduction mode) rather than in CCM (continuous-conduction mode). In DCM, the flyback converter is a first-order system at low frequencies, which eases the feedback-loop compensation. You can use a low-cost secondary rectifier, thanks to soft blocking conditions. In DCM, IP goes to zero, and the diode stops conducting, whereas the power-switch turn-on event in CCM forces the diode to brutally stop conducting...

These units can be useful as a short-range, single-channel remote-control. When the pushbutton in the transmitter circuit is briefly activated, the LED D1 in the receiver illuminates and an optional beeper or relay can be operated...

The magnetic proximity switch circuit, in principle, consists of a reed switch at its heart. When a magnet is brought in the vicinity of the sensor (reed switch), it operates and controls the rest of the switching circuit. In place of the reed switch, one may, as well, use a general-purpose electromagnetic reed relay (by making use of the reed switch contacts) as the sensor, if required. These tiny reed relays are easily available as they are widely used in telecom products. The reed switch or relay to be used with this circuit should be the normally open type...

Here`s the schematic of the device depicted in the photo. Each of the ten coil-assemblies has its own copy of the above circuit...

Click on a component to visit its circuit description. "TP" indicates a test point, a convenient spot to connect your voltmeter...

Picured in Figure 1 is a miniature magnetic gun. When optimally tuned, it will propel a small slug about 1.5 metres high, or 2.5 metres horizontally. IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15 is taken low through the "Fire" button. IC2 then sequences through outputs Q1 to Q7, to feed power transistors TR1 to TR4, which fire electromagnets L1 to L4 in rapid sequence...