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The frequencies are plotted for a nominal supply voltage of 12 V, however, this voltage is not critical, and a supply of between 5 V and 15 Leektor may in fact be used. By connecting additional modules as shown in Figure ele,tor the circuit may be extended almost in- In order to store digital information on a mag- netic tape or to transmit it over long-distance telephone lines, use is often made of a modu- lator which converts the digital signal into an FSK Frequency Shift Keyed signal.
These consist of an exposed wire el- ement 3301 on a ceramic former, and are pro- vided with contact dips that may be fixed any- where 3011 the length of the element, 1 kW electric fire heating elements which have a re- sistance of around elektkr Q may also be used. For this reason, ‘abbrevia ted’ type numbers are used in Elektor wherever possible: If desired, a 1 k preset may be included in series with PI to allow easier fine tuning. At the same time the inter- nal oscillator begins feeding pulses to the coun- ter.
P2 can then be used to calibrate the ammeter. The ac- companying figure shows a circuit diagram of a simple and reliable FSK modulator which has the advantage of requiring no calibration. A V 1 A thyristor should also prove suitable. The relationship between voltage and fre- quency is given by: This current will also flow through Tl and the zener. A conventional IF transformer is used to determine the frequency, The alignment generator is tuned to the correct frequency by passing the output signal through a ceramic IF filter.
The output from the temperature sensor in the iron is con- nected to the inverting input and compared with a reference voltage at the non-inverting input, set by PI. This is rich in harmonics and, due to the extremely small duty- cycle of the waveform, the power consumed by the output stage, T2, is fairly small. The result is that the chip, and hence the refer- ence voltage, is held at a virtually constant tem- perature.
An ideal basis for constructional projects and a comprehensive source of ideas for anyone interested in elec- tronics.
Elektor – Circuits : Free Download, Borrow, and Streaming : Internet Archive
Care should then be taken that the magnetic field of the trans- former does not affect the performance of the oscilloscope. Although a higher output frequency is possible, there is a corre- sponding deterioration in the waveform. With S4 in the left-hand position the output of the disc preamp can be tapped off and fed to the tape decks, while SI can be in any of its four positions, thus allowing disc or some other source to be listened to at the same time.
When the upper pair of contacts is bridged the input of N1 is taken high, so the output goes high. Cl now charges via PI so that the input voltage of N1 falls until the flip-flop is set and the Q output goes high. The current consumption of the preamp is extremely low, elektoe 1.
The most useful way of doing this is to frequency-scale the input signal, by means of a bucket-brigade elekotr logue delay lineso that the display fits in nicely with the available sweep speed.
The only constraint on the operation of the cir- cuit is that the interval between successive oper- ations of the switch must be at least half a sec- ond to allow Cl time to charge and discharge. D1 and D2 are included to stabilise the reference voltage.
The circuit can be elektod as it stands as a hum rejection filter in harmonic distortion meters or as a hum filter for TV sound signals. So long as the voltage on its inverting input is less than the analogue input voltage on its non -inverting input the output is high. Knotted handkerchief Since the advent of paper handkerchiefs, that time-honoured method of jogging a forgetful memory, namely tying a knot in one’s hanky, has been faced with practical difficulties.
Complete circuit of the function generator. An input signal of sufficient amplitude to over- Figure 1. Photo 1 shows an oscillograph of the complete test waveform, while photo 2 shows the pulses as seen on a cor- rectly calibrated oscilloscope.
Elektor – 301 Circuits.pdf
Obviously, if Vi is less than V A then Vg will be a negative voltage. This signal is fed back via Cl to the dlektor of the Schmitt trigger. Braun Automatic mono stereo switch For some time now owners of stereo FM re- ceivers will have noticed that the stereo indicator lamp stays on continuously. This is driven from an identical astable to that in figure 1b, While the output of Nl is low and Cl is charg- ing, the output of N2 is high and C2 is discharg- ing into C3, and vice versa.
The IC can be a general purpose op-amp such as a3 orThe compensation capacitor C2 is not required if a is used since this IC is internally compensated.
The signal level is increased until elsktor be- comes apparent, whereupon PI is adjusted to minimise distortion. When the voltage on C2 equals that at the non- inverting input the output of IC1 goes low. The result is that the brightness of the lighting varies with the speed of the train, and if the train is actually stopped, then the lighting will be completely extinguished.
Elektor – 301 Circuits
The circuit uses only three ICs, five resistors and a capaci- tor. Wirewound resistors are available with high power ratings, but unfortunately such resistors are rarely wound so as to minimise self- inductance.
The input signal is fed to a two- stage amplifier, each stage consisting of a pair of DC-coupled transistors. PI should be adjusted so that the voltage at the test elektpr shown in figure 1 is between