Turck's TB-Q08 RFID read/write head measures just 32 x 20 x 8 mm with integrated antenna, electronics and two LEDs visible from all directions.
Presented here is a simple circuit that can drive two motors for a small robot, allowing the robot to negotiate an obstacle course. Two light-dependent resistors (LDRs) are used to detect the obstacle and the motors are driven correspondingly to avoid the obstacles automatically. Two H-bridge motor circuits are used that can drive each motor forward or backward, or stop it, independently.
According to a post by Edward Aten, we would spend a total of 3.5 days untangling headphones over the course of our life. No wonder why Apple is looking to kill the headphones in its future phones.Aten decided to do the math to see how much time is wasted when we endlessly try to untangle our headphones. So, what did he do to arrive on that number?
A single layer coil has two advantages. Firstly, like all air core coils, it is free from 'iron losses' and the non-linearity mentioned above. Secondly, single layer coils have the additional advantage of low self-capacitance and thus high self-resonant frequency. These coils are mostly used above about 3 Mhz.
In the simple case of a single layer solenoidal coil the inductance may be estimated as follows (Wheeler)
L = 0.001 N2r2 / (228r + 254l)
where L is the inductance in henrys, r is the coil radius in metres, l is the coil length in metres (>0.8r) and N is the number of turns.
This formula applies at 'low' frequencies. At frequencies high enough for skin effect to occur a correction of up to about -2% is made.
To construct a self-supporting air cored coil take a length of plain 1 millimetre diameter copper wire and hold one end in a bench vice. Take the other end in a pair of pliers and pull until the wire has stretched slightly - this will straighten it. Using a 5 millimetre diameter drill bit wrap the wire around it until enough turns have been applied. Using 'long nosed' pliers bend the ends of the coil to get them into a radial position.
Small reductions in the inductance obtained can be achieved by pulling the turns apart slightly. This will also reduce self-resonance. Other combinations of wire and coil diameter may be tried but best results are usually obtained when the length of the coil is the same as its diameter.
This property also leads to a disadvantage of the air cored coil: microphony. If you need good frequency stability in the presence of vibration then wind the coil on a support made from a suitable plastic or ceramic former.
From pacemakers to insulin pumps, electronic implants are a powerful medical tool, but they present their own suite of risks — scarring, rejection and sepsis among them. Now a team of researchers has createda dissolving electronic implant, sort of like a much more sophisticated version of dissolving sutures. Sutures, however, can’t be injected into a rat’s brain, and don’t come equipped with temporary Wi-Fi.
In recent years, light-emitting diode (LED) technology has made impressive gains in price, performance and manufacturability. Further improvements that optimise LED operation are expected to drive exponential growth in the LED lighting market. One of the most recent commercial developments is a family of high-voltage LEDs (AC LEDs) that can operate directly off line voltage without the need for an AC-DC converter.